wireprotov2: support response caching

One of the things I've learned from managing VCS servers over the
years is that they are hard to scale. It is well known that some
companies have very beefy (read: very expensive) servers to power
their VCS needs. It is also known that specialized servers for
various VCS exist in order to facilitate scaling servers. (Mercurial
is in this boat.)

One of the aspects that make a VCS server hard to scale is the
high CPU load incurred by constant client clone/pull operations.

To alleviate the scaling pain associated with data retrieval
operations, I want to integrate caching into the Mercurial wire
protocol server as robustly as possible such that servers can
aggressively cache responses and defer as much server load as
possible.

This commit represents the initial implementation of a general
caching layer in wire protocol version 2.

We define a new interface and behavior for a wire protocol cacher
in repository.py. (This is probably where a reviewer should look
first to understand what is going on.)

The bulk of the added code is in wireprotov2server.py, where we
define how a command can opt in to being cached and integrate
caching into command dispatching.

From a very high-level:

* A command can declare itself as cacheable by providing a callable
  that can be used to derive a cache key.
* At dispatch time, if a command is cacheable, we attempt to
  construct a cacher and use it for serving the request and/or
  caching the request.
* The dispatch layer handles the bulk of the business logic for
  caching, making cachers mostly "dumb content stores."
* The mechanism for invalidating cached entries (one of the harder
  parts about caching in general) is by varying the cache key when
  state changes. As such, cachers don't need to be concerned with
  cache invalidation.

Initially, we've hooked up support for caching "manifestdata" and
"filedata" commands. These are the simplest to cache, as they should
be immutable over time. Caching of commands related to changeset
data is a bit harder (because cache validation is impacted by
changes to bookmarks, phases, etc). This will be implemented later.
(Strictly speaking, censoring a file should invalidate caches. I've
added an inline TODO to track this edge case.)

To prove it works, this commit implements a test-only extension
providing in-memory caching backed by an lrucachedict. A new test
showing this extension behaving properly is added. FWIW, the
cacher is ~50 lines of code, demonstrating the relative ease with
which a cache can be added to a server.

While the test cacher is not suitable for production workloads, just
for kicks I performed a clone of just the changeset and manifest data
for the mozilla-unified repository. With a fully warmed cache (of just
the manifest data since changeset data is not cached), server-side
CPU usage dropped from ~73s to ~28s. That's pretty significant and
demonstrates the potential that response caching has on server
scalability!

Differential Revision: https://phab.mercurial-scm.org/D4773

tests/test-wireproto-caching.t

@@ -0,0 +1,645
+  $ . $TESTDIR/wireprotohelpers.sh
+  $ cat >> $HGRCPATH << EOF
+  > [extensions]
+  > blackbox =
+  > [blackbox]
+  > track = simplecache
+  > EOF
+  $ hg init server
+  $ enablehttpv2 server
+  $ cd server
+  $ cat >> .hg/hgrc << EOF
+  > [extensions]
+  > simplecache = $TESTDIR/wireprotosimplecache.py
+  > EOF
+
+  $ echo a0 > a
+  $ echo b0 > b
+  $ hg -q commit -A -m 'commit 0'
+  $ echo a1 > a
+  $ hg commit -m 'commit 1'
+  $ echo b1 > b
+  $ hg commit -m 'commit 2'
+  $ echo a2 > a
+  $ echo b2 > b
+  $ hg commit -m 'commit 3'
+
+  $ hg log -G -T '{rev}:{node} {desc}'
+  @  3:50590a86f3ff5d1e9a1624a7a6957884565cc8e8 commit 3
+  |
+  o  2:4d01eda50c6ac5f7e89cbe1880143a32f559c302 commit 2
+  |
+  o  1:4432d83626e8a98655f062ec1f2a43b07f7fbbb0 commit 1
+  |
+  o  0:3390ef850073fbc2f0dfff2244342c8e9229013a commit 0
+  
+
+  $ hg --debug debugindex -m
+     rev linkrev nodeid                                   p1                                       p2
+       0       0 992f4779029a3df8d0666d00bb924f69634e2641 0000000000000000000000000000000000000000 0000000000000000000000000000000000000000
+       1       1 a988fb43583e871d1ed5750ee074c6d840bbbfc8 992f4779029a3df8d0666d00bb924f69634e2641 0000000000000000000000000000000000000000
+       2       2 a8853dafacfca6fc807055a660d8b835141a3bb4 a988fb43583e871d1ed5750ee074c6d840bbbfc8 0000000000000000000000000000000000000000
+       3       3 3fe11dfbb13645782b0addafbe75a87c210ffddc a8853dafacfca6fc807055a660d8b835141a3bb4 0000000000000000000000000000000000000000
+
+  $ hg serve -p $HGPORT -d --pid-file hg.pid -E error.log
+  $ cat hg.pid > $DAEMON_PIDS
+
+Performing the same request should result in same result, with 2nd response
+coming from cache.
+
+  $ sendhttpv2peer << EOF
+  > command manifestdata
+  >     nodes eval:[b'\x99\x2f\x47\x79\x02\x9a\x3d\xf8\xd0\x66\x6d\x00\xbb\x92\x4f\x69\x63\x4e\x26\x41']
+  >     tree eval:b''
+  >     fields eval:[b'parents']
+  > EOF
+  creating http peer for wire protocol version 2
+  sending manifestdata command
+  s>     POST /api/exp-http-v2-0002/ro/manifestdata HTTP/1.1\r\n
+  s>     Accept-Encoding: identity\r\n
+  s>     accept: application/mercurial-exp-framing-0005\r\n
+  s>     content-type: application/mercurial-exp-framing-0005\r\n
+  s>     content-length: 83\r\n
+  s>     host: $LOCALIP:$HGPORT\r\n (glob)
+  s>     user-agent: Mercurial debugwireproto\r\n
+  s>     \r\n
+  s>     K\x00\x00\x01\x00\x01\x01\x11\xa2Dargs\xa3Ffields\x81GparentsEnodes\x81T\x99/Gy\x02\x9a=\xf8\xd0fm\x00\xbb\x92OicN&ADtree@DnameLmanifestdata
+  s> makefile('rb', None)
+  s>     HTTP/1.1 200 OK\r\n
+  s>     Server: testing stub value\r\n
+  s>     Date: $HTTP_DATE$\r\n
+  s>     Content-Type: application/mercurial-exp-framing-0005\r\n
+  s>     Transfer-Encoding: chunked\r\n
+  s>     \r\n
+  s>     13\r\n
+  s>     \x0b\x00\x00\x01\x00\x02\x011
+  s>     \xa1FstatusBok
+  s>     \r\n
+  received frame(size=11; request=1; stream=2; streamflags=stream-begin; type=command-response; flags=continuation)
+  s>     63\r\n
+  s>     [\x00\x00\x01\x00\x02\x001
+  s>     \xa1Jtotalitems\x01\xa2DnodeT\x99/Gy\x02\x9a=\xf8\xd0fm\x00\xbb\x92OicN&AGparents\x82T\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00T\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00
+  s>     \r\n
+  received frame(size=91; request=1; stream=2; streamflags=; type=command-response; flags=continuation)
+  s>     8\r\n
+  s>     \x00\x00\x00\x01\x00\x02\x002
+  s>     \r\n
+  s>     0\r\n
+  s>     \r\n
+  received frame(size=0; request=1; stream=2; streamflags=; type=command-response; flags=eos)
+  response: gen[
+    {
+      b'totalitems': 1
+    },
+    {
+      b'node': b'\x99/Gy\x02\x9a=\xf8\xd0fm\x00\xbb\x92OicN&A',
+      b'parents': [
+        b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00',
+        b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
+      ]
+    }
+  ]
+
+  $ sendhttpv2peer << EOF
+  > command manifestdata
+  >     nodes eval:[b'\x99\x2f\x47\x79\x02\x9a\x3d\xf8\xd0\x66\x6d\x00\xbb\x92\x4f\x69\x63\x4e\x26\x41']
+  >     tree eval:b''
+  >     fields eval:[b'parents']
+  > EOF
+  creating http peer for wire protocol version 2
+  sending manifestdata command
+  s>     POST /api/exp-http-v2-0002/ro/manifestdata HTTP/1.1\r\n
+  s>     Accept-Encoding: identity\r\n
+  s>     accept: application/mercurial-exp-framing-0005\r\n
+  s>     content-type: application/mercurial-exp-framing-0005\r\n
+  s>     content-length: 83\r\n
+  s>     host: $LOCALIP:$HGPORT\r\n (glob)
+  s>     user-agent: Mercurial debugwireproto\r\n
+  s>     \r\n
+  s>     K\x00\x00\x01\x00\x01\x01\x11\xa2Dargs\xa3Ffields\x81GparentsEnodes\x81T\x99/Gy\x02\x9a=\xf8\xd0fm\x00\xbb\x92OicN&ADtree@DnameLmanifestdata
+  s> makefile('rb', None)
+  s>     HTTP/1.1 200 OK\r\n
+  s>     Server: testing stub value\r\n
+  s>     Date: $HTTP_DATE$\r\n
+  s>     Content-Type: application/mercurial-exp-framing-0005\r\n
+  s>     Transfer-Encoding: chunked\r\n
+  s>     \r\n
+  s>     13\r\n
+  s>     \x0b\x00\x00\x01\x00\x02\x011
+  s>     \xa1FstatusBok
+  s>     \r\n
+  received frame(size=11; request=1; stream=2; streamflags=stream-begin; type=command-response; flags=continuation)
+  s>     63\r\n
+  s>     [\x00\x00\x01\x00\x02\x001
+  s>     \xa1Jtotalitems\x01\xa2DnodeT\x99/Gy\x02\x9a=\xf8\xd0fm\x00\xbb\x92OicN&AGparents\x82T\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00T\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00
+  s>     \r\n
+  received frame(size=91; request=1; stream=2; streamflags=; type=command-response; flags=continuation)
+  s>     8\r\n
+  s>     \x00\x00\x00\x01\x00\x02\x002
+  s>     \r\n
+  s>     0\r\n
+  s>     \r\n
+  received frame(size=0; request=1; stream=2; streamflags=; type=command-response; flags=eos)
+  response: gen[
+    {
+      b'totalitems': 1
+    },
+    {
+      b'node': b'\x99/Gy\x02\x9a=\xf8\xd0fm\x00\xbb\x92OicN&A',
+      b'parents': [
+        b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00',
+        b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
+      ]
+    }
+  ]
+
+Sending different request doesn't yield cache hit.
+
+  $ sendhttpv2peer << EOF
+  > command manifestdata
+  >     nodes eval:[b'\x99\x2f\x47\x79\x02\x9a\x3d\xf8\xd0\x66\x6d\x00\xbb\x92\x4f\x69\x63\x4e\x26\x41', b'\xa9\x88\xfb\x43\x58\x3e\x87\x1d\x1e\xd5\x75\x0e\xe0\x74\xc6\xd8\x40\xbb\xbf\xc8']
+  >     tree eval:b''
+  >     fields eval:[b'parents']
+  > EOF
+  creating http peer for wire protocol version 2
+  sending manifestdata command
+  s>     POST /api/exp-http-v2-0002/ro/manifestdata HTTP/1.1\r\n
+  s>     Accept-Encoding: identity\r\n
+  s>     accept: application/mercurial-exp-framing-0005\r\n
+  s>     content-type: application/mercurial-exp-framing-0005\r\n
+  s>     content-length: 104\r\n
+  s>     host: $LOCALIP:$HGPORT\r\n (glob)
+  s>     user-agent: Mercurial debugwireproto\r\n
+  s>     \r\n
+  s>     `\x00\x00\x01\x00\x01\x01\x11\xa2Dargs\xa3Ffields\x81GparentsEnodes\x82T\x99/Gy\x02\x9a=\xf8\xd0fm\x00\xbb\x92OicN&AT\xa9\x88\xfbCX>\x87\x1d\x1e\xd5u\x0e\xe0t\xc6\xd8@\xbb\xbf\xc8Dtree@DnameLmanifestdata
+  s> makefile('rb', None)
+  s>     HTTP/1.1 200 OK\r\n
+  s>     Server: testing stub value\r\n
+  s>     Date: $HTTP_DATE$\r\n
+  s>     Content-Type: application/mercurial-exp-framing-0005\r\n
+  s>     Transfer-Encoding: chunked\r\n
+  s>     \r\n
+  s>     13\r\n
+  s>     \x0b\x00\x00\x01\x00\x02\x011
+  s>     \xa1FstatusBok
+  s>     \r\n
+  received frame(size=11; request=1; stream=2; streamflags=stream-begin; type=command-response; flags=continuation)
+  s>     b1\r\n
+  s>     \xa9\x00\x00\x01\x00\x02\x001
+  s>     \xa1Jtotalitems\x02\xa2DnodeT\x99/Gy\x02\x9a=\xf8\xd0fm\x00\xbb\x92OicN&AGparents\x82T\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00T\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\xa2DnodeT\xa9\x88\xfbCX>\x87\x1d\x1e\xd5u\x0e\xe0t\xc6\xd8@\xbb\xbf\xc8Gparents\x82T\x99/Gy\x02\x9a=\xf8\xd0fm\x00\xbb\x92OicN&AT\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00
+  s>     \r\n
+  received frame(size=169; request=1; stream=2; streamflags=; type=command-response; flags=continuation)
+  s>     8\r\n
+  s>     \x00\x00\x00\x01\x00\x02\x002
+  s>     \r\n
+  s>     0\r\n
+  s>     \r\n
+  received frame(size=0; request=1; stream=2; streamflags=; type=command-response; flags=eos)
+  response: gen[
+    {
+      b'totalitems': 2
+    },
+    {
+      b'node': b'\x99/Gy\x02\x9a=\xf8\xd0fm\x00\xbb\x92OicN&A',
+      b'parents': [
+        b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00',
+        b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
+      ]
+    },
+    {
+      b'node': b'\xa9\x88\xfbCX>\x87\x1d\x1e\xd5u\x0e\xe0t\xc6\xd8@\xbb\xbf\xc8',
+      b'parents': [
+        b'\x99/Gy\x02\x9a=\xf8\xd0fm\x00\xbb\x92OicN&A',
+        b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
+      ]
+    }
+  ]
+
+  $ cat .hg/blackbox.log
+  *> cacher constructed for manifestdata (glob)
+  *> cache miss for c045a581599d58608efd3d93d8129841f2af04a0 (glob)
+  *> storing cache entry for c045a581599d58608efd3d93d8129841f2af04a0 (glob)
+  *> cacher constructed for manifestdata (glob)
+  *> cache hit for c045a581599d58608efd3d93d8129841f2af04a0 (glob)
+  *> cacher constructed for manifestdata (glob)
+  *> cache miss for 6ed2f740a1cdd12c9e99c4f27695543143c26a11 (glob)
+  *> storing cache entry for 6ed2f740a1cdd12c9e99c4f27695543143c26a11 (glob)
+
+  $ cat error.log
+
+  $ killdaemons.py
+  $ rm .hg/blackbox.log
+
+Try with object caching mode
+
+  $ cat >> .hg/hgrc << EOF
+  > [simplecache]
+  > cacheobjects = true
+  > EOF
+
+  $ hg serve -p $HGPORT -d --pid-file hg.pid -E error.log
+  $ cat hg.pid > $DAEMON_PIDS
+
+  $ sendhttpv2peer << EOF
+  > command manifestdata
+  >     nodes eval:[b'\x99\x2f\x47\x79\x02\x9a\x3d\xf8\xd0\x66\x6d\x00\xbb\x92\x4f\x69\x63\x4e\x26\x41']
+  >     tree eval:b''
+  >     fields eval:[b'parents']
+  > EOF
+  creating http peer for wire protocol version 2
+  sending manifestdata command
+  s>     POST /api/exp-http-v2-0002/ro/manifestdata HTTP/1.1\r\n
+  s>     Accept-Encoding: identity\r\n
+  s>     accept: application/mercurial-exp-framing-0005\r\n
+  s>     content-type: application/mercurial-exp-framing-0005\r\n
+  s>     content-length: 83\r\n
+  s>     host: $LOCALIP:$HGPORT\r\n (glob)
+  s>     user-agent: Mercurial debugwireproto\r\n
+  s>     \r\n
+  s>     K\x00\x00\x01\x00\x01\x01\x11\xa2Dargs\xa3Ffields\x81GparentsEnodes\x81T\x99/Gy\x02\x9a=\xf8\xd0fm\x00\xbb\x92OicN&ADtree@DnameLmanifestdata
+  s> makefile('rb', None)
+  s>     HTTP/1.1 200 OK\r\n
+  s>     Server: testing stub value\r\n
+  s>     Date: $HTTP_DATE$\r\n
+  s>     Content-Type: application/mercurial-exp-framing-0005\r\n
+  s>     Transfer-Encoding: chunked\r\n
+  s>     \r\n
+  s>     13\r\n
+  s>     \x0b\x00\x00\x01\x00\x02\x011
+  s>     \xa1FstatusBok
+  s>     \r\n
+  received frame(size=11; request=1; stream=2; streamflags=stream-begin; type=command-response; flags=continuation)
+  s>     63\r\n
+  s>     [\x00\x00\x01\x00\x02\x001
+  s>     \xa1Jtotalitems\x01\xa2DnodeT\x99/Gy\x02\x9a=\xf8\xd0fm\x00\xbb\x92OicN&AGparents\x82T\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00T\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00
+  s>     \r\n
+  received frame(size=91; request=1; stream=2; streamflags=; type=command-response; flags=continuation)
+  s>     8\r\n
+  s>     \x00\x00\x00\x01\x00\x02\x002
+  s>     \r\n
+  s>     0\r\n
+  s>     \r\n
+  received frame(size=0; request=1; stream=2; streamflags=; type=command-response; flags=eos)
+  response: gen[
+    {
+      b'totalitems': 1
+    },
+    {
+      b'node': b'\x99/Gy\x02\x9a=\xf8\xd0fm\x00\xbb\x92OicN&A',
+      b'parents': [
+        b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00',
+        b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
+      ]
+    }
+  ]
+
+  $ sendhttpv2peer << EOF
+  > command manifestdata
+  >     nodes eval:[b'\x99\x2f\x47\x79\x02\x9a\x3d\xf8\xd0\x66\x6d\x00\xbb\x92\x4f\x69\x63\x4e\x26\x41']
+  >     tree eval:b''
+  >     fields eval:[b'parents']
+  > EOF
+  creating http peer for wire protocol version 2
+  sending manifestdata command
+  s>     POST /api/exp-http-v2-0002/ro/manifestdata HTTP/1.1\r\n
+  s>     Accept-Encoding: identity\r\n
+  s>     accept: application/mercurial-exp-framing-0005\r\n
+  s>     content-type: application/mercurial-exp-framing-0005\r\n
+  s>     content-length: 83\r\n
+  s>     host: $LOCALIP:$HGPORT\r\n (glob)
+  s>     user-agent: Mercurial debugwireproto\r\n
+  s>     \r\n
+  s>     K\x00\x00\x01\x00\x01\x01\x11\xa2Dargs\xa3Ffields\x81GparentsEnodes\x81T\x99/Gy\x02\x9a=\xf8\xd0fm\x00\xbb\x92OicN&ADtree@DnameLmanifestdata
+  s> makefile('rb', None)
+  s>     HTTP/1.1 200 OK\r\n
+  s>     Server: testing stub value\r\n
+  s>     Date: $HTTP_DATE$\r\n
+  s>     Content-Type: application/mercurial-exp-framing-0005\r\n
+  s>     Transfer-Encoding: chunked\r\n
+  s>     \r\n
+  s>     13\r\n
+  s>     \x0b\x00\x00\x01\x00\x02\x011
+  s>     \xa1FstatusBok
+  s>     \r\n
+  received frame(size=11; request=1; stream=2; streamflags=stream-begin; type=command-response; flags=continuation)
+  s>     63\r\n
+  s>     [\x00\x00\x01\x00\x02\x001
+  s>     \xa1Jtotalitems\x01\xa2DnodeT\x99/Gy\x02\x9a=\xf8\xd0fm\x00\xbb\x92OicN&AGparents\x82T\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00T\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00
+  s>     \r\n
+  received frame(size=91; request=1; stream=2; streamflags=; type=command-response; flags=continuation)
+  s>     8\r\n
+  s>     \x00\x00\x00\x01\x00\x02\x002
+  s>     \r\n
+  s>     0\r\n
+  s>     \r\n
+  received frame(size=0; request=1; stream=2; streamflags=; type=command-response; flags=eos)
+  response: gen[
+    {
+      b'totalitems': 1
+    },
+    {
+      b'node': b'\x99/Gy\x02\x9a=\xf8\xd0fm\x00\xbb\x92OicN&A',
+      b'parents': [
+        b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00',
+        b'\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00\x00'
+      ]
+    }
+  ]
+
+  $ cat .hg/blackbox.log
+  *> cacher constructed for manifestdata (glob)
+  *> cache miss for c045a581599d58608efd3d93d8129841f2af04a0 (glob)
+  *> storing cache entry for c045a581599d58608efd3d93d8129841f2af04a0 (glob)
+  *> cacher constructed for manifestdata (glob)
+  *> cache hit for c045a581599d58608efd3d93d8129841f2af04a0 (glob)
+
+  $ cat error.log
+
+  $ killdaemons.py
+  $ rm .hg/blackbox.log
+
+A non-cacheable command does not instantiate cacher
+
+  $ hg serve -p $HGPORT -d --pid-file hg.pid -E error.log
+  $ cat hg.pid > $DAEMON_PIDS
+  $ sendhttpv2peer << EOF
+  > command capabilities
+  > EOF
+  creating http peer for wire protocol version 2
+  sending capabilities command
+  s>     POST /api/exp-http-v2-0002/ro/capabilities HTTP/1.1\r\n
+  s>     Accept-Encoding: identity\r\n
+  s>     accept: application/mercurial-exp-framing-0005\r\n
+  s>     content-type: application/mercurial-exp-framing-0005\r\n
+  s>     content-length: 27\r\n
+  s>     host: $LOCALIP:$HGPORT\r\n (glob)
+  s>     user-agent: Mercurial debugwireproto\r\n
+  s>     \r\n
+  s>     \x13\x00\x00\x01\x00\x01\x01\x11\xa1DnameLcapabilities
+  s> makefile('rb', None)
+  s>     HTTP/1.1 200 OK\r\n
+  s>     Server: testing stub value\r\n
+  s>     Date: $HTTP_DATE$\r\n
+  s>     Content-Type: application/mercurial-exp-framing-0005\r\n
+  s>     Transfer-Encoding: chunked\r\n
+  s>     \r\n
+  s>     13\r\n
+  s>     \x0b\x00\x00\x01\x00\x02\x011
+  s>     \xa1FstatusBok
+  s>     \r\n
+  received frame(size=11; request=1; stream=2; streamflags=stream-begin; type=command-response; flags=continuation)
+  s>     52b\r\n
+  s>     #\x05\x00\x01\x00\x02\x001
+  s>     \xa5Hcommands\xaaIbranchmap\xa2Dargs\xa0Kpermissions\x81DpullLcapabilities\xa2Dargs\xa0Kpermissions\x81DpullMchangesetdata\xa2Dargs\xa4Ffields\xa4Gdefault\xd9\x01\x02\x80Hrequired\xf4DtypeCsetKvalidvalues\xd9\x01\x02\x84IbookmarksGparentsEphaseHrevisionInoderange\xa3Gdefault\xf6Hrequired\xf4DtypeDlistEnodes\xa3Gdefault\xf6Hrequired\xf4DtypeDlistJnodesdepth\xa3Gdefault\xf6Hrequired\xf4DtypeCintKpermissions\x81DpullHfiledata\xa2Dargs\xa4Ffields\xa4Gdefault\xd9\x01\x02\x80Hrequired\xf4DtypeCsetKvalidvalues\xd9\x01\x02\x82GparentsHrevisionKhaveparents\xa3Gdefault\xf4Hrequired\xf4DtypeDboolEnodes\xa2Hrequired\xf5DtypeDlistDpath\xa2Hrequired\xf5DtypeEbytesKpermissions\x81DpullEheads\xa2Dargs\xa1Jpubliconly\xa3Gdefault\xf4Hrequired\xf4DtypeDboolKpermissions\x81DpullEknown\xa2Dargs\xa1Enodes\xa3Gdefault\x80Hrequired\xf4DtypeDlistKpermissions\x81DpullHlistkeys\xa2Dargs\xa1Inamespace\xa2Hrequired\xf5DtypeEbytesKpermissions\x81DpullFlookup\xa2Dargs\xa1Ckey\xa2Hrequired\xf5DtypeEbytesKpermissions\x81DpullLmanifestdata\xa2Dargs\xa4Ffields\xa4Gdefault\xd9\x01\x02\x80Hrequired\xf4DtypeCsetKvalidvalues\xd9\x01\x02\x82GparentsHrevisionKhaveparents\xa3Gdefault\xf4Hrequired\xf4DtypeDboolEnodes\xa2Hrequired\xf5DtypeDlistDtree\xa2Hrequired\xf5DtypeEbytesKpermissions\x81DpullGpushkey\xa2Dargs\xa4Ckey\xa2Hrequired\xf5DtypeEbytesInamespace\xa2Hrequired\xf5DtypeEbytesCnew\xa2Hrequired\xf5DtypeEbytesCold\xa2Hrequired\xf5DtypeEbytesKpermissions\x81DpushKcompression\x82\xa1DnameDzstd\xa1DnameDzlibQframingmediatypes\x81X&application/mercurial-exp-framing-0005Rpathfilterprefixes\xd9\x01\x02\x82Epath:Lrootfilesin:Nrawrepoformats\x82LgeneraldeltaHrevlogv1
+  s>     \r\n
+  received frame(size=1315; request=1; stream=2; streamflags=; type=command-response; flags=continuation)
+  s>     8\r\n
+  s>     \x00\x00\x00\x01\x00\x02\x002
+  s>     \r\n
+  s>     0\r\n
+  s>     \r\n
+  received frame(size=0; request=1; stream=2; streamflags=; type=command-response; flags=eos)
+  response: gen[
+    {
+      b'commands': {
+        b'branchmap': {
+          b'args': {},
+          b'permissions': [
+            b'pull'
+          ]
+        },
+        b'capabilities': {
+          b'args': {},
+          b'permissions': [
+            b'pull'
+          ]
+        },
+        b'changesetdata': {
+          b'args': {
+            b'fields': {
+              b'default': set([]),
+              b'required': False,
+              b'type': b'set',
+              b'validvalues': set([
+                b'bookmarks',
+                b'parents',
+                b'phase',
+                b'revision'
+              ])
+            },
+            b'noderange': {
+              b'default': None,
+              b'required': False,
+              b'type': b'list'
+            },
+            b'nodes': {
+              b'default': None,
+              b'required': False,
+              b'type': b'list'
+            },
+            b'nodesdepth': {
+              b'default': None,
+              b'required': False,
+              b'type': b'int'
+            }
+          },
+          b'permissions': [
+            b'pull'
+          ]
+        },
+        b'filedata': {
+          b'args': {
+            b'fields': {
+              b'default': set([]),
+              b'required': False,
+              b'type': b'set',
+              b'validvalues': set([
+                b'parents',
+                b'revision'
+              ])
+            },
+            b'haveparents': {
+              b'default': False,
+              b'required': False,
+              b'type': b'bool'
+            },
+            b'nodes': {
+              b'required': True,
+              b'type': b'list'
+            },
+            b'path': {
+              b'required': True,
+              b'type': b'bytes'
+            }
+          },
+          b'permissions': [
+            b'pull'
+          ]
+        },
+        b'heads': {
+          b'args': {
+            b'publiconly': {
+              b'default': False,
+              b'required': False,
+              b'type': b'bool'
+            }
+          },
+          b'permissions': [
+            b'pull'
+          ]
+        },
+        b'known': {
+          b'args': {
+            b'nodes': {
+              b'default': [],
+              b'required': False,
+              b'type': b'list'
+            }
+          },
+          b'permissions': [
+            b'pull'
+          ]
+        },
+        b'listkeys': {
+          b'args': {
+            b'namespace': {
+              b'required': True,
+              b'type': b'bytes'
+            }
+          },
+          b'permissions': [
+            b'pull'
+          ]
+        },
+        b'lookup': {
+          b'args': {
+            b'key': {
+              b'required': True,
+              b'type': b'bytes'
+            }
+          },
+          b'permissions': [
+            b'pull'
+          ]
+        },
+        b'manifestdata': {
+          b'args': {
+            b'fields': {
+              b'default': set([]),
+              b'required': False,
+              b'type': b'set',
+              b'validvalues': set([
+                b'parents',
+                b'revision'
+              ])
+            },
+            b'haveparents': {
+              b'default': False,
+              b'required': False,
+              b'type': b'bool'
+            },
+            b'nodes': {
+              b'required': True,
+              b'type': b'list'
+            },
+            b'tree': {
+              b'required': True,
+              b'type': b'bytes'
+            }
+          },
+          b'permissions': [
+            b'pull'
+          ]
+        },
+        b'pushkey': {
+          b'args': {
+            b'key': {
+              b'required': True,
+              b'type': b'bytes'
+            },
+            b'namespace': {
+              b'required': True,
+              b'type': b'bytes'
+            },
+            b'new': {
+              b'required': True,
+              b'type': b'bytes'
+            },
+            b'old': {
+              b'required': True,
+              b'type': b'bytes'
+            }
+          },
+          b'permissions': [
+            b'push'
+          ]
+        }
+      },
+      b'compression': [
+        {
+          b'name': b'zstd'
+        },
+        {
+          b'name': b'zlib'
+        }
+      ],
+      b'framingmediatypes': [
+        b'application/mercurial-exp-framing-0005'
+      ],
+      b'pathfilterprefixes': set([
+        b'path:',
+        b'rootfilesin:'
+      ]),
+      b'rawrepoformats': [
+        b'generaldelta',
+        b'revlogv1'
+      ]
+    }
+  ]
+
+  $ test -f .hg/blackbox.log
+  [1]
+
+An error is not cached
+
+  $ sendhttpv2peer << EOF
+  > command manifestdata
+  >     nodes eval:[b'\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa']
+  >     tree eval:b''
+  >     fields eval:[b'parents']
+  > EOF
+  creating http peer for wire protocol version 2
+  sending manifestdata command
+  s>     POST /api/exp-http-v2-0002/ro/manifestdata HTTP/1.1\r\n
+  s>     Accept-Encoding: identity\r\n
+  s>     accept: application/mercurial-exp-framing-0005\r\n
+  s>     content-type: application/mercurial-exp-framing-0005\r\n
+  s>     content-length: 83\r\n
+  s>     host: $LOCALIP:$HGPORT\r\n (glob)
+  s>     user-agent: Mercurial debugwireproto\r\n
+  s>     \r\n
+  s>     K\x00\x00\x01\x00\x01\x01\x11\xa2Dargs\xa3Ffields\x81GparentsEnodes\x81T\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaaDtree@DnameLmanifestdata
+  s> makefile('rb', None)
+  s>     HTTP/1.1 200 OK\r\n
+  s>     Server: testing stub value\r\n
+  s>     Date: $HTTP_DATE$\r\n
+  s>     Content-Type: application/mercurial-exp-framing-0005\r\n
+  s>     Transfer-Encoding: chunked\r\n
+  s>     \r\n
+  s>     51\r\n
+  s>     I\x00\x00\x01\x00\x02\x012
+  s>     \xa2Eerror\xa2Dargs\x81T\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaaGmessagePunknown node: %sFstatusEerror
+  s>     \r\n
+  received frame(size=73; request=1; stream=2; streamflags=stream-begin; type=command-response; flags=eos)
+  s>     0\r\n
+  s>     \r\n
+  abort: unknown node: \xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa\xaa! (esc)
+  [255]
+
+  $ cat .hg/blackbox.log
+  *> cacher constructed for manifestdata (glob)
+  *> cache miss for 9d1bb421d99e913d45f2d099aa49728514292dd2 (glob)
+  *> cacher exiting due to error (glob)
+
+  $ killdaemons.py
+  $ rm .hg/blackbox.log

tests/wireprotosimplecache.py

@@ -0,0 +1,100
+# wireprotosimplecache.py - Extension providing in-memory wire protocol cache
+#
+# Copyright 2018 Gregory Szorc <[e-mail]>
+#
+# This software may be used and distributed according to the terms of the
+# GNU General Public License version 2 or any later version.
+
+from __future__ import absolute_import
+
+from mercurial import (
+    extensions,
+    registrar,
+    repository,
+    util,
+    wireprototypes,
+    wireprotov2server,
+)
+from mercurial.utils import (
+    interfaceutil,
+)
+
+CACHE = None
+
+configtable = {}
+configitem = registrar.configitem(configtable)
+
+configitem('simplecache', 'cacheobjects',
+           default=False)
+
[e-mail](repository.iwireprotocolcommandcacher)
+class memorycacher(object):
+    def __init__(self, ui, command, encodefn):
+        self.ui = ui
+        self.encodefn = encodefn
+        self.key = None
+        self.cacheobjects = ui.configbool('simplecache', 'cacheobjects')
+        self.buffered = []
+
+        ui.log('simplecache', 'cacher constructed for %s\n', command)
+
+    def __enter__(self):
+        return self
+
+    def __exit__(self, exctype, excvalue, exctb):
+        if exctype:
+            self.ui.log('simplecache', 'cacher exiting due to error\n')
+
+    def adjustcachekeystate(self, state):
+        # Needed in order to make tests deterministic. Don't copy this
+        # pattern for production caches!
+        del state[b'repo']
+
+    def setcachekey(self, key):
+        self.key = key
+        return True
+
+    def lookup(self):
+        if self.key not in CACHE:
+            self.ui.log('simplecache', 'cache miss for %s\n', self.key)
+            return None
+
+        entry = CACHE[self.key]
+        self.ui.log('simplecache', 'cache hit for %s\n', self.key)
+
+        if self.cacheobjects:
+            return {
+                'objs': entry,
+            }
+        else:
+            return {
+                'objs': [wireprototypes.encodedresponse(entry)],
+            }
+
+    def onobject(self, obj):
+        if self.cacheobjects:
+            self.buffered.append(obj)
+        else:
+            self.buffered.extend(self.encodefn(obj))
+
+        yield obj
+
+    def onfinished(self):
+        self.ui.log('simplecache', 'storing cache entry for %s\n', self.key)
+        if self.cacheobjects:
+            CACHE[self.key] = self.buffered
+        else:
+            CACHE[self.key] = b''.join(self.buffered)
+
+        return []
+
+def makeresponsecacher(orig, repo, proto, command, args, objencoderfn):
+    return memorycacher(repo.ui, command, objencoderfn)
+
+def extsetup(ui):
+    global CACHE
+
+    CACHE = util.lrucachedict(10000)
+
+    extensions.wrapfunction(wireprotov2server, 'makeresponsecacher',
+                            makeresponsecacher)

mercurial/repository.py

@@ -1,1659 +1,1816
 # repository.py - Interfaces and base classes for repositories and peers.
 #
 # Copyright 2017 Gregory Szorc <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 from __future__ import absolute_import
 
 from .i18n import _
 from . import (
     error,
 )
 from .utils import (
     interfaceutil,
 )
 
 # When narrowing is finalized and no longer subject to format changes,
 # we should move this to just "narrow" or similar.
 NARROW_REQUIREMENT = 'narrowhg-experimental'
 
 # Local repository feature string.
 
 # Revlogs are being used for file storage.
 REPO_FEATURE_REVLOG_FILE_STORAGE = b'revlogfilestorage'
 # The storage part of the repository is shared from an external source.
 REPO_FEATURE_SHARED_STORAGE = b'sharedstore'
 # LFS supported for backing file storage.
 REPO_FEATURE_LFS = b'lfs'
 
 class ipeerconnection(interfaceutil.Interface):
     """Represents a "connection" to a repository.
 
     This is the base interface for representing a connection to a repository.
     It holds basic properties and methods applicable to all peer types.
 
     This is not a complete interface definition and should not be used
     outside of this module.
     """
     ui = interfaceutil.Attribute("""ui.ui instance""")
 
     def url():
         """Returns a URL string representing this peer.
 
         Currently, implementations expose the raw URL used to construct the
         instance. It may contain credentials as part of the URL. The
         expectations of the value aren't well-defined and this could lead to
         data leakage.
 
         TODO audit/clean consumers and more clearly define the contents of this
         value.
         """
 
     def local():
         """Returns a local repository instance.
 
         If the peer represents a local repository, returns an object that
         can be used to interface with it. Otherwise returns ``None``.
         """
 
     def peer():
         """Returns an object conforming to this interface.
 
         Most implementations will ``return self``.
         """
 
     def canpush():
         """Returns a boolean indicating if this peer can be pushed to."""
 
     def close():
         """Close the connection to this peer.
 
         This is called when the peer will no longer be used. Resources
         associated with the peer should be cleaned up.
         """
 
 class ipeercapabilities(interfaceutil.Interface):
     """Peer sub-interface related to capabilities."""
 
     def capable(name):
         """Determine support for a named capability.
 
         Returns ``False`` if capability not supported.
 
         Returns ``True`` if boolean capability is supported. Returns a string
         if capability support is non-boolean.
 
         Capability strings may or may not map to wire protocol capabilities.
         """
 
     def requirecap(name, purpose):
         """Require a capability to be present.
 
         Raises a ``CapabilityError`` if the capability isn't present.
         """
 
 class ipeercommands(interfaceutil.Interface):
     """Client-side interface for communicating over the wire protocol.
 
     This interface is used as a gateway to the Mercurial wire protocol.
     methods commonly call wire protocol commands of the same name.
     """
 
     def branchmap():
         """Obtain heads in named branches.
 
         Returns a dict mapping branch name to an iterable of nodes that are
         heads on that branch.
         """
 
     def capabilities():
         """Obtain capabilities of the peer.
 
         Returns a set of string capabilities.
         """
 
     def clonebundles():
         """Obtains the clone bundles manifest for the repo.
 
         Returns the manifest as unparsed bytes.
         """
 
     def debugwireargs(one, two, three=None, four=None, five=None):
         """Used to facilitate debugging of arguments passed over the wire."""
 
     def getbundle(source, **kwargs):
         """Obtain remote repository data as a bundle.
 
         This command is how the bulk of repository data is transferred from
         the peer to the local repository
 
         Returns a generator of bundle data.
         """
 
     def heads():
         """Determine all known head revisions in the peer.
 
         Returns an iterable of binary nodes.
         """
 
     def known(nodes):
         """Determine whether multiple nodes are known.
 
         Accepts an iterable of nodes whose presence to check for.
 
         Returns an iterable of booleans indicating of the corresponding node
         at that index is known to the peer.
         """
 
     def listkeys(namespace):
         """Obtain all keys in a pushkey namespace.
 
         Returns an iterable of key names.
         """
 
     def lookup(key):
         """Resolve a value to a known revision.
 
         Returns a binary node of the resolved revision on success.
         """
 
     def pushkey(namespace, key, old, new):
         """Set a value using the ``pushkey`` protocol.
 
         Arguments correspond to the pushkey namespace and key to operate on and
         the old and new values for that key.
 
         Returns a string with the peer result. The value inside varies by the
         namespace.
         """
 
     def stream_out():
         """Obtain streaming clone data.
 
         Successful result should be a generator of data chunks.
         """
 
     def unbundle(bundle, heads, url):
         """Transfer repository data to the peer.
 
         This is how the bulk of data during a push is transferred.
 
         Returns the integer number of heads added to the peer.
         """
 
 class ipeerlegacycommands(interfaceutil.Interface):
     """Interface for implementing support for legacy wire protocol commands.
 
     Wire protocol commands transition to legacy status when they are no longer
     used by modern clients. To facilitate identifying which commands are
     legacy, the interfaces are split.
     """
 
     def between(pairs):
         """Obtain nodes between pairs of nodes.
 
         ``pairs`` is an iterable of node pairs.
 
         Returns an iterable of iterables of nodes corresponding to each
         requested pair.
         """
 
     def branches(nodes):
         """Obtain ancestor changesets of specific nodes back to a branch point.
 
         For each requested node, the peer finds the first ancestor node that is
         a DAG root or is a merge.
 
         Returns an iterable of iterables with the resolved values for each node.
         """
 
     def changegroup(nodes, source):
         """Obtain a changegroup with data for descendants of specified nodes."""
 
     def changegroupsubset(bases, heads, source):
         pass
 
 class ipeercommandexecutor(interfaceutil.Interface):
     """Represents a mechanism to execute remote commands.
 
     This is the primary interface for requesting that wire protocol commands
     be executed. Instances of this interface are active in a context manager
     and have a well-defined lifetime. When the context manager exits, all
     outstanding requests are waited on.
     """
 
     def callcommand(name, args):
         """Request that a named command be executed.
 
         Receives the command name and a dictionary of command arguments.
 
         Returns a ``concurrent.futures.Future`` that will resolve to the
         result of that command request. That exact value is left up to
         the implementation and possibly varies by command.
 
         Not all commands can coexist with other commands in an executor
         instance: it depends on the underlying wire protocol transport being
         used and the command itself.
 
         Implementations MAY call ``sendcommands()`` automatically if the
         requested command can not coexist with other commands in this executor.
 
         Implementations MAY call ``sendcommands()`` automatically when the
         future's ``result()`` is called. So, consumers using multiple
         commands with an executor MUST ensure that ``result()`` is not called
         until all command requests have been issued.
         """
 
     def sendcommands():
         """Trigger submission of queued command requests.
 
         Not all transports submit commands as soon as they are requested to
         run. When called, this method forces queued command requests to be
         issued. It will no-op if all commands have already been sent.
 
         When called, no more new commands may be issued with this executor.
         """
 
     def close():
         """Signal that this command request is finished.
 
         When called, no more new commands may be issued. All outstanding
         commands that have previously been issued are waited on before
         returning. This not only includes waiting for the futures to resolve,
         but also waiting for all response data to arrive. In other words,
         calling this waits for all on-wire state for issued command requests
         to finish.
 
         When used as a context manager, this method is called when exiting the
         context manager.
 
         This method may call ``sendcommands()`` if there are buffered commands.
         """
 
 class ipeerrequests(interfaceutil.Interface):
     """Interface for executing commands on a peer."""
 
     def commandexecutor():
         """A context manager that resolves to an ipeercommandexecutor.
 
         The object this resolves to can be used to issue command requests
         to the peer.
 
         Callers should call its ``callcommand`` method to issue command
         requests.
 
         A new executor should be obtained for each distinct set of commands
         (possibly just a single command) that the consumer wants to execute
         as part of a single operation or round trip. This is because some
         peers are half-duplex and/or don't support persistent connections.
         e.g. in the case of HTTP peers, commands sent to an executor represent
         a single HTTP request. While some peers may support multiple command
         sends over the wire per executor, consumers need to code to the least
         capable peer. So it should be assumed that command executors buffer
         called commands until they are told to send them and that each
         command executor could result in a new connection or wire-level request
         being issued.
         """
 
 class ipeerbase(ipeerconnection, ipeercapabilities, ipeerrequests):
     """Unified interface for peer repositories.
 
     All peer instances must conform to this interface.
     """
 
 @interfaceutil.implementer(ipeerbase)
 class peer(object):
     """Base class for peer repositories."""
 
     def capable(self, name):
         caps = self.capabilities()
         if name in caps:
             return True
 
         name = '%s=' % name
         for cap in caps:
             if cap.startswith(name):
                 return cap[len(name):]
 
         return False
 
     def requirecap(self, name, purpose):
         if self.capable(name):
             return
 
         raise error.CapabilityError(
             _('cannot %s; remote repository does not support the %r '
               'capability') % (purpose, name))
 
 class iverifyproblem(interfaceutil.Interface):
     """Represents a problem with the integrity of the repository.
 
     Instances of this interface are emitted to describe an integrity issue
     with a repository (e.g. corrupt storage, missing data, etc).
 
     Instances are essentially messages associated with severity.
     """
     warning = interfaceutil.Attribute(
         """Message indicating a non-fatal problem.""")
 
     error = interfaceutil.Attribute(
         """Message indicating a fatal problem.""")
 
     node = interfaceutil.Attribute(
         """Revision encountering the problem.
 
         ``None`` means the problem doesn't apply to a single revision.
         """)
 
 class irevisiondelta(interfaceutil.Interface):
     """Represents a delta between one revision and another.
 
     Instances convey enough information to allow a revision to be exchanged
     with another repository.
 
     Instances represent the fulltext revision data or a delta against
     another revision. Therefore the ``revision`` and ``delta`` attributes
     are mutually exclusive.
 
     Typically used for changegroup generation.
     """
 
     node = interfaceutil.Attribute(
         """20 byte node of this revision.""")
 
     p1node = interfaceutil.Attribute(
         """20 byte node of 1st parent of this revision.""")
 
     p2node = interfaceutil.Attribute(
         """20 byte node of 2nd parent of this revision.""")
 
     linknode = interfaceutil.Attribute(
         """20 byte node of the changelog revision this node is linked to.""")
 
     flags = interfaceutil.Attribute(
         """2 bytes of integer flags that apply to this revision.""")
 
     basenode = interfaceutil.Attribute(
         """20 byte node of the revision this data is a delta against.
 
         ``nullid`` indicates that the revision is a full revision and not
         a delta.
         """)
 
     baserevisionsize = interfaceutil.Attribute(
         """Size of base revision this delta is against.
 
         May be ``None`` if ``basenode`` is ``nullid``.
         """)
 
     revision = interfaceutil.Attribute(
         """Raw fulltext of revision data for this node.""")
 
     delta = interfaceutil.Attribute(
         """Delta between ``basenode`` and ``node``.
 
         Stored in the bdiff delta format.
         """)
 
 class ifilerevisionssequence(interfaceutil.Interface):
     """Contains index data for all revisions of a file.
 
     Types implementing this behave like lists of tuples. The index
     in the list corresponds to the revision number. The values contain
     index metadata.
 
     The *null* revision (revision number -1) is always the last item
     in the index.
     """
 
     def __len__():
         """The total number of revisions."""
 
     def __getitem__(rev):
         """Returns the object having a specific revision number.
 
         Returns an 8-tuple with the following fields:
 
         offset+flags
            Contains the offset and flags for the revision. 64-bit unsigned
            integer where first 6 bytes are the offset and the next 2 bytes
            are flags. The offset can be 0 if it is not used by the store.
         compressed size
             Size of the revision data in the store. It can be 0 if it isn't
             needed by the store.
         uncompressed size
             Fulltext size. It can be 0 if it isn't needed by the store.
         base revision
             Revision number of revision the delta for storage is encoded
             against. -1 indicates not encoded against a base revision.
         link revision
             Revision number of changelog revision this entry is related to.
         p1 revision
             Revision number of 1st parent. -1 if no 1st parent.
         p2 revision
             Revision number of 2nd parent. -1 if no 1st parent.
         node
             Binary node value for this revision number.
 
         Negative values should index off the end of the sequence. ``-1``
         should return the null revision. ``-2`` should return the most
         recent revision.
         """
 
     def __contains__(rev):
         """Whether a revision number exists."""
 
     def insert(self, i, entry):
         """Add an item to the index at specific revision."""
 
 class ifileindex(interfaceutil.Interface):
     """Storage interface for index data of a single file.
 
     File storage data is divided into index metadata and data storage.
     This interface defines the index portion of the interface.
 
     The index logically consists of:
 
     * A mapping between revision numbers and nodes.
     * DAG data (storing and querying the relationship between nodes).
     * Metadata to facilitate storage.
     """
     def __len__():
         """Obtain the number of revisions stored for this file."""
 
     def __iter__():
         """Iterate over revision numbers for this file."""
 
     def revs(start=0, stop=None):
         """Iterate over revision numbers for this file, with control."""
 
     def parents(node):
         """Returns a 2-tuple of parent nodes for a revision.
 
         Values will be ``nullid`` if the parent is empty.
         """
 
     def parentrevs(rev):
         """Like parents() but operates on revision numbers."""
 
     def rev(node):
         """Obtain the revision number given a node.
 
         Raises ``error.LookupError`` if the node is not known.
         """
 
     def node(rev):
         """Obtain the node value given a revision number.
 
         Raises ``IndexError`` if the node is not known.
         """
 
     def lookup(node):
         """Attempt to resolve a value to a node.
 
         Value can be a binary node, hex node, revision number, or a string
         that can be converted to an integer.
 
         Raises ``error.LookupError`` if a node could not be resolved.
         """
 
     def linkrev(rev):
         """Obtain the changeset revision number a revision is linked to."""
 
     def iscensored(rev):
         """Return whether a revision's content has been censored."""
 
     def commonancestorsheads(node1, node2):
         """Obtain an iterable of nodes containing heads of common ancestors.
 
         See ``ancestor.commonancestorsheads()``.
         """
 
     def descendants(revs):
         """Obtain descendant revision numbers for a set of revision numbers.
 
         If ``nullrev`` is in the set, this is equivalent to ``revs()``.
         """
 
     def heads(start=None, stop=None):
         """Obtain a list of nodes that are DAG heads, with control.
 
         The set of revisions examined can be limited by specifying
         ``start`` and ``stop``. ``start`` is a node. ``stop`` is an
         iterable of nodes. DAG traversal starts at earlier revision
         ``start`` and iterates forward until any node in ``stop`` is
         encountered.
         """
 
     def children(node):
         """Obtain nodes that are children of a node.
 
         Returns a list of nodes.
         """
 
 class ifiledata(interfaceutil.Interface):
     """Storage interface for data storage of a specific file.
 
     This complements ``ifileindex`` and provides an interface for accessing
     data for a tracked file.
     """
     def size(rev):
         """Obtain the fulltext size of file data.
 
         Any metadata is excluded from size measurements.
         """
 
     def revision(node, raw=False):
         """"Obtain fulltext data for a node.
 
         By default, any storage transformations are applied before the data
         is returned. If ``raw`` is True, non-raw storage transformations
         are not applied.
 
         The fulltext data may contain a header containing metadata. Most
         consumers should use ``read()`` to obtain the actual file data.
         """
 
     def read(node):
         """Resolve file fulltext data.
 
         This is similar to ``revision()`` except any metadata in the data
         headers is stripped.
         """
 
     def renamed(node):
         """Obtain copy metadata for a node.
 
         Returns ``False`` if no copy metadata is stored or a 2-tuple of
         (path, node) from which this revision was copied.
         """
 
     def cmp(node, fulltext):
         """Compare fulltext to another revision.
 
         Returns True if the fulltext is different from what is stored.
 
         This takes copy metadata into account.
 
         TODO better document the copy metadata and censoring logic.
         """
 
     def emitrevisions(nodes,
                       nodesorder=None,
                       revisiondata=False,
                       assumehaveparentrevisions=False,
                       deltaprevious=False):
         """Produce ``irevisiondelta`` for revisions.
 
         Given an iterable of nodes, emits objects conforming to the
         ``irevisiondelta`` interface that describe revisions in storage.
 
         This method is a generator.
 
         The input nodes may be unordered. Implementations must ensure that a
         node's parents are emitted before the node itself. Transitively, this
         means that a node may only be emitted once all its ancestors in
         ``nodes`` have also been emitted.
 
         By default, emits "index" data (the ``node``, ``p1node``, and
         ``p2node`` attributes). If ``revisiondata`` is set, revision data
         will also be present on the emitted objects.
 
         With default argument values, implementations can choose to emit
         either fulltext revision data or a delta. When emitting deltas,
         implementations must consider whether the delta's base revision
         fulltext is available to the receiver.
 
         The base revision fulltext is guaranteed to be available if any of
         the following are met:
 
         * Its fulltext revision was emitted by this method call.
         * A delta for that revision was emitted by this method call.
         * ``assumehaveparentrevisions`` is True and the base revision is a
           parent of the node.
 
         ``nodesorder`` can be used to control the order that revisions are
         emitted. By default, revisions can be reordered as long as they are
         in DAG topological order (see above). If the value is ``nodes``,
         the iteration order from ``nodes`` should be used. If the value is
         ``storage``, then the native order from the backing storage layer
         is used. (Not all storage layers will have strong ordering and behavior
         of this mode is storage-dependent.) ``nodes`` ordering can force
         revisions to be emitted before their ancestors, so consumers should
         use it with care.
 
         The ``linknode`` attribute on the returned ``irevisiondelta`` may not
         be set and it is the caller's responsibility to resolve it, if needed.
 
         If ``deltaprevious`` is True and revision data is requested, all
         revision data should be emitted as deltas against the revision
         emitted just prior. The initial revision should be a delta against
         its 1st parent.
         """
 
 class ifilemutation(interfaceutil.Interface):
     """Storage interface for mutation events of a tracked file."""
 
     def add(filedata, meta, transaction, linkrev, p1, p2):
         """Add a new revision to the store.
 
         Takes file data, dictionary of metadata, a transaction, linkrev,
         and parent nodes.
 
         Returns the node that was added.
 
         May no-op if a revision matching the supplied data is already stored.
         """
 
     def addrevision(revisiondata, transaction, linkrev, p1, p2, node=None,
                     flags=0, cachedelta=None):
         """Add a new revision to the store.
 
         This is similar to ``add()`` except it operates at a lower level.
 
         The data passed in already contains a metadata header, if any.
 
         ``node`` and ``flags`` can be used to define the expected node and
         the flags to use with storage.
 
         ``add()`` is usually called when adding files from e.g. the working
         directory. ``addrevision()`` is often called by ``add()`` and for
         scenarios where revision data has already been computed, such as when
         applying raw data from a peer repo.
         """
 
     def addgroup(deltas, linkmapper, transaction, addrevisioncb=None):
         """Process a series of deltas for storage.
 
         ``deltas`` is an iterable of 7-tuples of
         (node, p1, p2, linknode, deltabase, delta, flags) defining revisions
         to add.
 
         The ``delta`` field contains ``mpatch`` data to apply to a base
         revision, identified by ``deltabase``. The base node can be
         ``nullid``, in which case the header from the delta can be ignored
         and the delta used as the fulltext.
 
         ``addrevisioncb`` should be called for each node as it is committed.
 
         Returns a list of nodes that were processed. A node will be in the list
         even if it existed in the store previously.
         """
 
     def censorrevision(tr, node, tombstone=b''):
         """Remove the content of a single revision.
 
         The specified ``node`` will have its content purged from storage.
         Future attempts to access the revision data for this node will
         result in failure.
 
         A ``tombstone`` message can optionally be stored. This message may be
         displayed to users when they attempt to access the missing revision
         data.
 
         Storage backends may have stored deltas against the previous content
         in this revision. As part of censoring a revision, these storage
         backends are expected to rewrite any internally stored deltas such
         that they no longer reference the deleted content.
         """
 
     def getstrippoint(minlink):
         """Find the minimum revision that must be stripped to strip a linkrev.
 
         Returns a 2-tuple containing the minimum revision number and a set
         of all revisions numbers that would be broken by this strip.
 
         TODO this is highly revlog centric and should be abstracted into
         a higher-level deletion API. ``repair.strip()`` relies on this.
         """
 
     def strip(minlink, transaction):
         """Remove storage of items starting at a linkrev.
 
         This uses ``getstrippoint()`` to determine the first node to remove.
         Then it effectively truncates storage for all revisions after that.
 
         TODO this is highly revlog centric and should be abstracted into a
         higher-level deletion API.
         """
 
 class ifilestorage(ifileindex, ifiledata, ifilemutation):
     """Complete storage interface for a single tracked file."""
 
     def files():
         """Obtain paths that are backing storage for this file.
 
         TODO this is used heavily by verify code and there should probably
         be a better API for that.
         """
 
     def storageinfo(exclusivefiles=False, sharedfiles=False,
                     revisionscount=False, trackedsize=False,
                     storedsize=False):
         """Obtain information about storage for this file's data.
 
         Returns a dict describing storage for this tracked path. The keys
         in the dict map to arguments of the same. The arguments are bools
         indicating whether to calculate and obtain that data.
 
         exclusivefiles
            Iterable of (vfs, path) describing files that are exclusively
            used to back storage for this tracked path.
 
         sharedfiles
            Iterable of (vfs, path) describing files that are used to back
            storage for this tracked path. Those files may also provide storage
            for other stored entities.
 
         revisionscount
            Number of revisions available for retrieval.
 
         trackedsize
            Total size in bytes of all tracked revisions. This is a sum of the
            length of the fulltext of all revisions.
 
         storedsize
            Total size in bytes used to store data for all tracked revisions.
            This is commonly less than ``trackedsize`` due to internal usage
            of deltas rather than fulltext revisions.
 
         Not all storage backends may support all queries are have a reasonable
         value to use. In that case, the value should be set to ``None`` and
         callers are expected to handle this special value.
         """
 
     def verifyintegrity(state):
         """Verifies the integrity of file storage.
 
         ``state`` is a dict holding state of the verifier process. It can be
         used to communicate data between invocations of multiple storage
         primitives.
 
         If individual revisions cannot have their revision content resolved,
         the method is expected to set the ``skipread`` key to a set of nodes
         that encountered problems.
 
         The method yields objects conforming to the ``iverifyproblem``
         interface.
         """
 
 class idirs(interfaceutil.Interface):
     """Interface representing a collection of directories from paths.
 
     This interface is essentially a derived data structure representing
     directories from a collection of paths.
     """
 
     def addpath(path):
         """Add a path to the collection.
 
         All directories in the path will be added to the collection.
         """
 
     def delpath(path):
         """Remove a path from the collection.
 
         If the removal was the last path in a particular directory, the
         directory is removed from the collection.
         """
 
     def __iter__():
         """Iterate over the directories in this collection of paths."""
 
     def __contains__(path):
         """Whether a specific directory is in this collection."""
 
 class imanifestdict(interfaceutil.Interface):
     """Interface representing a manifest data structure.
 
     A manifest is effectively a dict mapping paths to entries. Each entry
     consists of a binary node and extra flags affecting that entry.
     """
 
     def __getitem__(path):
         """Returns the binary node value for a path in the manifest.
 
         Raises ``KeyError`` if the path does not exist in the manifest.
 
         Equivalent to ``self.find(path)[0]``.
         """
 
     def find(path):
         """Returns the entry for a path in the manifest.
 
         Returns a 2-tuple of (node, flags).
 
         Raises ``KeyError`` if the path does not exist in the manifest.
         """
 
     def __len__():
         """Return the number of entries in the manifest."""
 
     def __nonzero__():
         """Returns True if the manifest has entries, False otherwise."""
 
     __bool__ = __nonzero__
 
     def __setitem__(path, node):
         """Define the node value for a path in the manifest.
 
         If the path is already in the manifest, its flags will be copied to
         the new entry.
         """
 
     def __contains__(path):
         """Whether a path exists in the manifest."""
 
     def __delitem__(path):
         """Remove a path from the manifest.
 
         Raises ``KeyError`` if the path is not in the manifest.
         """
 
     def __iter__():
         """Iterate over paths in the manifest."""
 
     def iterkeys():
         """Iterate over paths in the manifest."""
 
     def keys():
         """Obtain a list of paths in the manifest."""
 
     def filesnotin(other, match=None):
         """Obtain the set of paths in this manifest but not in another.
 
         ``match`` is an optional matcher function to be applied to both
         manifests.
 
         Returns a set of paths.
         """
 
     def dirs():
         """Returns an object implementing the ``idirs`` interface."""
 
     def hasdir(dir):
         """Returns a bool indicating if a directory is in this manifest."""
 
     def matches(match):
         """Generate a new manifest filtered through a matcher.
 
         Returns an object conforming to the ``imanifestdict`` interface.
         """
 
     def walk(match):
         """Generator of paths in manifest satisfying a matcher.
 
         This is equivalent to ``self.matches(match).iterkeys()`` except a new
         manifest object is not created.
 
         If the matcher has explicit files listed and they don't exist in
         the manifest, ``match.bad()`` is called for each missing file.
         """
 
     def diff(other, match=None, clean=False):
         """Find differences between this manifest and another.
 
         This manifest is compared to ``other``.
 
         If ``match`` is provided, the two manifests are filtered against this
         matcher and only entries satisfying the matcher are compared.
 
         If ``clean`` is True, unchanged files are included in the returned
         object.
 
         Returns a dict with paths as keys and values of 2-tuples of 2-tuples of
         the form ``((node1, flag1), (node2, flag2))`` where ``(node1, flag1)``
         represents the node and flags for this manifest and ``(node2, flag2)``
         are the same for the other manifest.
         """
 
     def setflag(path, flag):
         """Set the flag value for a given path.
 
         Raises ``KeyError`` if the path is not already in the manifest.
         """
 
     def get(path, default=None):
         """Obtain the node value for a path or a default value if missing."""
 
     def flags(path, default=''):
         """Return the flags value for a path or a default value if missing."""
 
     def copy():
         """Return a copy of this manifest."""
 
     def items():
         """Returns an iterable of (path, node) for items in this manifest."""
 
     def iteritems():
         """Identical to items()."""
 
     def iterentries():
         """Returns an iterable of (path, node, flags) for this manifest.
 
         Similar to ``iteritems()`` except items are a 3-tuple and include
         flags.
         """
 
     def text():
         """Obtain the raw data representation for this manifest.
 
         Result is used to create a manifest revision.
         """
 
     def fastdelta(base, changes):
         """Obtain a delta between this manifest and another given changes.
 
         ``base`` in the raw data representation for another manifest.
 
         ``changes`` is an iterable of ``(path, to_delete)``.
 
         Returns a 2-tuple containing ``bytearray(self.text())`` and the
         delta between ``base`` and this manifest.
         """
 
 class imanifestrevisionbase(interfaceutil.Interface):
     """Base interface representing a single revision of a manifest.
 
     Should not be used as a primary interface: should always be inherited
     as part of a larger interface.
     """
 
     def new():
         """Obtain a new manifest instance.
 
         Returns an object conforming to the ``imanifestrevisionwritable``
         interface. The instance will be associated with the same
         ``imanifestlog`` collection as this instance.
         """
 
     def copy():
         """Obtain a copy of this manifest instance.
 
         Returns an object conforming to the ``imanifestrevisionwritable``
         interface. The instance will be associated with the same
         ``imanifestlog`` collection as this instance.
         """
 
     def read():
         """Obtain the parsed manifest data structure.
 
         The returned object conforms to the ``imanifestdict`` interface.
         """
 
 class imanifestrevisionstored(imanifestrevisionbase):
     """Interface representing a manifest revision committed to storage."""
 
     def node():
         """The binary node for this manifest."""
 
     parents = interfaceutil.Attribute(
         """List of binary nodes that are parents for this manifest revision."""
     )
 
     def readdelta(shallow=False):
         """Obtain the manifest data structure representing changes from parent.
 
         This manifest is compared to its 1st parent. A new manifest representing
         those differences is constructed.
 
         The returned object conforms to the ``imanifestdict`` interface.
         """
 
     def readfast(shallow=False):
         """Calls either ``read()`` or ``readdelta()``.
 
         The faster of the two options is called.
         """
 
     def find(key):
         """Calls self.read().find(key)``.
 
         Returns a 2-tuple of ``(node, flags)`` or raises ``KeyError``.
         """
 
 class imanifestrevisionwritable(imanifestrevisionbase):
     """Interface representing a manifest revision that can be committed."""
 
     def write(transaction, linkrev, p1node, p2node, added, removed, match=None):
         """Add this revision to storage.
 
         Takes a transaction object, the changeset revision number it will
         be associated with, its parent nodes, and lists of added and
         removed paths.
 
         If match is provided, storage can choose not to inspect or write out
         items that do not match. Storage is still required to be able to provide
         the full manifest in the future for any directories written (these
         manifests should not be "narrowed on disk").
 
         Returns the binary node of the created revision.
         """
 
 class imanifeststorage(interfaceutil.Interface):
     """Storage interface for manifest data."""
 
     tree = interfaceutil.Attribute(
         """The path to the directory this manifest tracks.
 
         The empty bytestring represents the root manifest.
         """)
 
     index = interfaceutil.Attribute(
         """An ``ifilerevisionssequence`` instance.""")
 
     indexfile = interfaceutil.Attribute(
         """Path of revlog index file.
 
         TODO this is revlog specific and should not be exposed.
         """)
 
     opener = interfaceutil.Attribute(
         """VFS opener to use to access underlying files used for storage.
 
         TODO this is revlog specific and should not be exposed.
         """)
 
     version = interfaceutil.Attribute(
         """Revlog version number.
 
         TODO this is revlog specific and should not be exposed.
         """)
 
     _generaldelta = interfaceutil.Attribute(
         """Whether generaldelta storage is being used.
 
         TODO this is revlog specific and should not be exposed.
         """)
 
     fulltextcache = interfaceutil.Attribute(
         """Dict with cache of fulltexts.
 
         TODO this doesn't feel appropriate for the storage interface.
         """)
 
     def __len__():
         """Obtain the number of revisions stored for this manifest."""
 
     def __iter__():
         """Iterate over revision numbers for this manifest."""
 
     def rev(node):
         """Obtain the revision number given a binary node.
 
         Raises ``error.LookupError`` if the node is not known.
         """
 
     def node(rev):
         """Obtain the node value given a revision number.
 
         Raises ``error.LookupError`` if the revision is not known.
         """
 
     def lookup(value):
         """Attempt to resolve a value to a node.
 
         Value can be a binary node, hex node, revision number, or a bytes
         that can be converted to an integer.
 
         Raises ``error.LookupError`` if a ndoe could not be resolved.
         """
 
     def parents(node):
         """Returns a 2-tuple of parent nodes for a node.
 
         Values will be ``nullid`` if the parent is empty.
         """
 
     def parentrevs(rev):
         """Like parents() but operates on revision numbers."""
 
     def linkrev(rev):
         """Obtain the changeset revision number a revision is linked to."""
 
     def revision(node, _df=None, raw=False):
         """Obtain fulltext data for a node."""
 
     def revdiff(rev1, rev2):
         """Obtain a delta between two revision numbers.
 
         The returned data is the result of ``bdiff.bdiff()`` on the raw
         revision data.
         """
 
     def cmp(node, fulltext):
         """Compare fulltext to another revision.
 
         Returns True if the fulltext is different from what is stored.
         """
 
     def emitrevisions(nodes,
                       nodesorder=None,
                       revisiondata=False,
                       assumehaveparentrevisions=False):
         """Produce ``irevisiondelta`` describing revisions.
 
         See the documentation for ``ifiledata`` for more.
         """
 
     def addgroup(deltas, linkmapper, transaction, addrevisioncb=None):
         """Process a series of deltas for storage.
 
         See the documentation in ``ifilemutation`` for more.
         """
 
     def rawsize(rev):
         """Obtain the size of tracked data.
 
         Is equivalent to ``len(m.revision(node, raw=True))``.
 
         TODO this method is only used by upgrade code and may be removed.
         """
 
     def getstrippoint(minlink):
         """Find minimum revision that must be stripped to strip a linkrev.
 
         See the documentation in ``ifilemutation`` for more.
         """
 
     def strip(minlink, transaction):
         """Remove storage of items starting at a linkrev.
 
         See the documentation in ``ifilemutation`` for more.
         """
 
     def checksize():
         """Obtain the expected sizes of backing files.
 
         TODO this is used by verify and it should not be part of the interface.
         """
 
     def files():
         """Obtain paths that are backing storage for this manifest.
 
         TODO this is used by verify and there should probably be a better API
         for this functionality.
         """
 
     def deltaparent(rev):
         """Obtain the revision that a revision is delta'd against.
 
         TODO delta encoding is an implementation detail of storage and should
         not be exposed to the storage interface.
         """
 
     def clone(tr, dest, **kwargs):
         """Clone this instance to another."""
 
     def clearcaches(clear_persisted_data=False):
         """Clear any caches associated with this instance."""
 
     def dirlog(d):
         """Obtain a manifest storage instance for a tree."""
 
     def add(m, transaction, link, p1, p2, added, removed, readtree=None,
             match=None):
         """Add a revision to storage.
 
         ``m`` is an object conforming to ``imanifestdict``.
 
         ``link`` is the linkrev revision number.
 
         ``p1`` and ``p2`` are the parent revision numbers.
 
         ``added`` and ``removed`` are iterables of added and removed paths,
         respectively.
 
         ``readtree`` is a function that can be used to read the child tree(s)
         when recursively writing the full tree structure when using
         treemanifets.
 
         ``match`` is a matcher that can be used to hint to storage that not all
         paths must be inspected; this is an optimization and can be safely
         ignored. Note that the storage must still be able to reproduce a full
         manifest including files that did not match.
         """
 
     def storageinfo(exclusivefiles=False, sharedfiles=False,
                     revisionscount=False, trackedsize=False,
                     storedsize=False):
         """Obtain information about storage for this manifest's data.
 
         See ``ifilestorage.storageinfo()`` for a description of this method.
         This one behaves the same way, except for manifest data.
         """
 
 class imanifestlog(interfaceutil.Interface):
     """Interface representing a collection of manifest snapshots.
 
     Represents the root manifest in a repository.
 
     Also serves as a means to access nested tree manifests and to cache
     tree manifests.
     """
 
     def __getitem__(node):
         """Obtain a manifest instance for a given binary node.
 
         Equivalent to calling ``self.get('', node)``.
 
         The returned object conforms to the ``imanifestrevisionstored``
         interface.
         """
 
     def get(tree, node, verify=True):
         """Retrieve the manifest instance for a given directory and binary node.
 
         ``node`` always refers to the node of the root manifest (which will be
         the only manifest if flat manifests are being used).
 
         If ``tree`` is the empty string, the root manifest is returned.
         Otherwise the manifest for the specified directory will be returned
         (requires tree manifests).
 
         If ``verify`` is True, ``LookupError`` is raised if the node is not
         known.
 
         The returned object conforms to the ``imanifestrevisionstored``
         interface.
         """
 
     def getstorage(tree):
         """Retrieve an interface to storage for a particular tree.
 
         If ``tree`` is the empty bytestring, storage for the root manifest will
         be returned. Otherwise storage for a tree manifest is returned.
 
         TODO formalize interface for returned object.
         """
 
     def clearcaches():
         """Clear caches associated with this collection."""
 
     def rev(node):
         """Obtain the revision number for a binary node.
 
         Raises ``error.LookupError`` if the node is not known.
         """
 
 class ilocalrepositoryfilestorage(interfaceutil.Interface):
     """Local repository sub-interface providing access to tracked file storage.
 
     This interface defines how a repository accesses storage for a single
     tracked file path.
     """
 
     def file(f):
         """Obtain a filelog for a tracked path.
 
         The returned type conforms to the ``ifilestorage`` interface.
         """
 
 class ilocalrepositorymain(interfaceutil.Interface):
     """Main interface for local repositories.
 
     This currently captures the reality of things - not how things should be.
     """
 
     supportedformats = interfaceutil.Attribute(
         """Set of requirements that apply to stream clone.
 
         This is actually a class attribute and is shared among all instances.
         """)
 
     supported = interfaceutil.Attribute(
         """Set of requirements that this repo is capable of opening.""")
 
     requirements = interfaceutil.Attribute(
         """Set of requirements this repo uses.""")
 
     features = interfaceutil.Attribute(
         """Set of "features" this repository supports.
 
         A "feature" is a loosely-defined term. It can refer to a feature
         in the classical sense or can describe an implementation detail
         of the repository. For example, a ``readonly`` feature may denote
         the repository as read-only. Or a ``revlogfilestore`` feature may
         denote that the repository is using revlogs for file storage.
 
         The intent of features is to provide a machine-queryable mechanism
         for repo consumers to test for various repository characteristics.
 
         Features are similar to ``requirements``. The main difference is that
         requirements are stored on-disk and represent requirements to open the
         repository. Features are more run-time capabilities of the repository
         and more granular capabilities (which may be derived from requirements).
         """)
 
     filtername = interfaceutil.Attribute(
         """Name of the repoview that is active on this repo.""")
 
     wvfs = interfaceutil.Attribute(
         """VFS used to access the working directory.""")
 
     vfs = interfaceutil.Attribute(
         """VFS rooted at the .hg directory.
 
         Used to access repository data not in the store.
         """)
 
     svfs = interfaceutil.Attribute(
         """VFS rooted at the store.
 
         Used to access repository data in the store. Typically .hg/store.
         But can point elsewhere if the store is shared.
         """)
 
     root = interfaceutil.Attribute(
         """Path to the root of the working directory.""")
 
     path = interfaceutil.Attribute(
         """Path to the .hg directory.""")
 
     origroot = interfaceutil.Attribute(
         """The filesystem path that was used to construct the repo.""")
 
     auditor = interfaceutil.Attribute(
         """A pathauditor for the working directory.
 
         This checks if a path refers to a nested repository.
 
         Operates on the filesystem.
         """)
 
     nofsauditor = interfaceutil.Attribute(
         """A pathauditor for the working directory.
 
         This is like ``auditor`` except it doesn't do filesystem checks.
         """)
 
     baseui = interfaceutil.Attribute(
         """Original ui instance passed into constructor.""")
 
     ui = interfaceutil.Attribute(
         """Main ui instance for this instance.""")
 
     sharedpath = interfaceutil.Attribute(
         """Path to the .hg directory of the repo this repo was shared from.""")
 
     store = interfaceutil.Attribute(
         """A store instance.""")
 
     spath = interfaceutil.Attribute(
         """Path to the store.""")
 
     sjoin = interfaceutil.Attribute(
         """Alias to self.store.join.""")
 
     cachevfs = interfaceutil.Attribute(
         """A VFS used to access the cache directory.
 
         Typically .hg/cache.
         """)
 
     filteredrevcache = interfaceutil.Attribute(
         """Holds sets of revisions to be filtered.""")
 
     names = interfaceutil.Attribute(
         """A ``namespaces`` instance.""")
 
     def close():
         """Close the handle on this repository."""
 
     def peer():
         """Obtain an object conforming to the ``peer`` interface."""
 
     def unfiltered():
         """Obtain an unfiltered/raw view of this repo."""
 
     def filtered(name, visibilityexceptions=None):
         """Obtain a named view of this repository."""
 
     obsstore = interfaceutil.Attribute(
         """A store of obsolescence data.""")
 
     changelog = interfaceutil.Attribute(
         """A handle on the changelog revlog.""")
 
     manifestlog = interfaceutil.Attribute(
         """An instance conforming to the ``imanifestlog`` interface.
 
         Provides access to manifests for the repository.
         """)
 
     dirstate = interfaceutil.Attribute(
         """Working directory state.""")
 
     narrowpats = interfaceutil.Attribute(
         """Matcher patterns for this repository's narrowspec.""")
 
     def narrowmatch():
         """Obtain a matcher for the narrowspec."""
 
     def setnarrowpats(newincludes, newexcludes):
         """Define the narrowspec for this repository."""
 
     def __getitem__(changeid):
         """Try to resolve a changectx."""
 
     def __contains__(changeid):
         """Whether a changeset exists."""
 
     def __nonzero__():
         """Always returns True."""
         return True
 
     __bool__ = __nonzero__
 
     def __len__():
         """Returns the number of changesets in the repo."""
 
     def __iter__():
         """Iterate over revisions in the changelog."""
 
     def revs(expr, *args):
         """Evaluate a revset.
 
         Emits revisions.
         """
 
     def set(expr, *args):
         """Evaluate a revset.
 
         Emits changectx instances.
         """
 
     def anyrevs(specs, user=False, localalias=None):
         """Find revisions matching one of the given revsets."""
 
     def url():
         """Returns a string representing the location of this repo."""
 
     def hook(name, throw=False, **args):
         """Call a hook."""
 
     def tags():
         """Return a mapping of tag to node."""
 
     def tagtype(tagname):
         """Return the type of a given tag."""
 
     def tagslist():
         """Return a list of tags ordered by revision."""
 
     def nodetags(node):
         """Return the tags associated with a node."""
 
     def nodebookmarks(node):
         """Return the list of bookmarks pointing to the specified node."""
 
     def branchmap():
         """Return a mapping of branch to heads in that branch."""
 
     def revbranchcache():
         pass
 
     def branchtip(branchtip, ignoremissing=False):
         """Return the tip node for a given branch."""
 
     def lookup(key):
         """Resolve the node for a revision."""
 
     def lookupbranch(key):
         """Look up the branch name of the given revision or branch name."""
 
     def known(nodes):
         """Determine whether a series of nodes is known.
 
         Returns a list of bools.
         """
 
     def local():
         """Whether the repository is local."""
         return True
 
     def publishing():
         """Whether the repository is a publishing repository."""
 
     def cancopy():
         pass
 
     def shared():
         """The type of shared repository or None."""
 
     def wjoin(f, *insidef):
         """Calls self.vfs.reljoin(self.root, f, *insidef)"""
 
     def setparents(p1, p2):
         """Set the parent nodes of the working directory."""
 
     def filectx(path, changeid=None, fileid=None):
         """Obtain a filectx for the given file revision."""
 
     def getcwd():
         """Obtain the current working directory from the dirstate."""
 
     def pathto(f, cwd=None):
         """Obtain the relative path to a file."""
 
     def adddatafilter(name, fltr):
         pass
 
     def wread(filename):
         """Read a file from wvfs, using data filters."""
 
     def wwrite(filename, data, flags, backgroundclose=False, **kwargs):
         """Write data to a file in the wvfs, using data filters."""
 
     def wwritedata(filename, data):
         """Resolve data for writing to the wvfs, using data filters."""
 
     def currenttransaction():
         """Obtain the current transaction instance or None."""
 
     def transaction(desc, report=None):
         """Open a new transaction to write to the repository."""
 
     def undofiles():
         """Returns a list of (vfs, path) for files to undo transactions."""
 
     def recover():
         """Roll back an interrupted transaction."""
 
     def rollback(dryrun=False, force=False):
         """Undo the last transaction.
 
         DANGEROUS.
         """
 
     def updatecaches(tr=None, full=False):
         """Warm repo caches."""
 
     def invalidatecaches():
         """Invalidate cached data due to the repository mutating."""
 
     def invalidatevolatilesets():
         pass
 
     def invalidatedirstate():
         """Invalidate the dirstate."""
 
     def invalidate(clearfilecache=False):
         pass
 
     def invalidateall():
         pass
 
     def lock(wait=True):
         """Lock the repository store and return a lock instance."""
 
     def wlock(wait=True):
         """Lock the non-store parts of the repository."""
 
     def currentwlock():
         """Return the wlock if it's held or None."""
 
     def checkcommitpatterns(wctx, vdirs, match, status, fail):
         pass
 
     def commit(text='', user=None, date=None, match=None, force=False,
                editor=False, extra=None):
         """Add a new revision to the repository."""
 
     def commitctx(ctx, error=False):
         """Commit a commitctx instance to the repository."""
 
     def destroying():
         """Inform the repository that nodes are about to be destroyed."""
 
     def destroyed():
         """Inform the repository that nodes have been destroyed."""
 
     def status(node1='.', node2=None, match=None, ignored=False,
                clean=False, unknown=False, listsubrepos=False):
         """Convenience method to call repo[x].status()."""
 
     def addpostdsstatus(ps):
         pass
 
     def postdsstatus():
         pass
 
     def clearpostdsstatus():
         pass
 
     def heads(start=None):
         """Obtain list of nodes that are DAG heads."""
 
     def branchheads(branch=None, start=None, closed=False):
         pass
 
     def branches(nodes):
         pass
 
     def between(pairs):
         pass
 
     def checkpush(pushop):
         pass
 
     prepushoutgoinghooks = interfaceutil.Attribute(
         """util.hooks instance.""")
 
     def pushkey(namespace, key, old, new):
         pass
 
     def listkeys(namespace):
         pass
 
     def debugwireargs(one, two, three=None, four=None, five=None):
         pass
 
     def savecommitmessage(text):
         pass
 
 class completelocalrepository(ilocalrepositorymain,
                               ilocalrepositoryfilestorage):
     """Complete interface for a local repository."""
+
+class iwireprotocolcommandcacher(interfaceutil.Interface):
+    """Represents a caching backend for wire protocol commands.
+
+    Wire protocol version 2 supports transparent caching of many commands.
+    To leverage this caching, servers can activate objects that cache
+    command responses. Objects handle both cache writing and reading.
+    This interface defines how that response caching mechanism works.
+
+    Wire protocol version 2 commands emit a series of objects that are
+    serialized and sent to the client. The caching layer exists between
+    the invocation of the command function and the sending of its output
+    objects to an output layer.
+
+    Instances of this interface represent a binding to a cache that
+    can serve a response (in place of calling a command function) and/or
+    write responses to a cache for subsequent use.
+
+    When a command request arrives, the following happens with regards
+    to this interface:
+
+    1. The server determines whether the command request is cacheable.
+    2. If it is, an instance of this interface is spawned.
+    3. The cacher is activated in a context manager (``__enter__`` is called).
+    4. A cache *key* for that request is derived. This will call the
+       instance's ``adjustcachekeystate()`` method so the derivation
+       can be influenced.
+    5. The cacher is informed of the derived cache key via a call to
+       ``setcachekey()``.
+    6. The cacher's ``lookup()`` method is called to test for presence of
+       the derived key in the cache.
+    7. If ``lookup()`` returns a hit, that cached result is used in place
+       of invoking the command function. ``__exit__`` is called and the instance
+       is discarded.
+    8. The command function is invoked.
+    9. ``onobject()`` is called for each object emitted by the command
+       function.
+    10. After the final object is seen, ``onoutputfinished()`` is called.
+    11. ``__exit__`` is called to signal the end of use of the instance.
+
+    Cache *key* derivation can be influenced by the instance.
+
+    Cache keys are initially derived by a deterministic representation of
+    the command request. This includes the command name, arguments, protocol
+    version, etc. This initial key derivation is performed by CBOR-encoding a
+    data structure and feeding that output into a hasher.
+
+    Instances of this interface can influence this initial key derivation
+    via ``adjustcachekeystate()``.
+
+    The instance is informed of the derived cache key via a call to
+    ``setcachekey()``. The instance must store the key locally so it can
+    be consulted on subsequent operations that may require it.
+
+    When constructed, the instance has access to a callable that can be used
+    for encoding response objects. This callable receives as its single
+    argument an object emitted by a command function. It returns an iterable
+    of bytes chunks representing the encoded object. Unless the cacher is
+    caching native Python objects in memory or has a way of reconstructing
+    the original Python objects, implementations typically call this function
+    to produce bytes from the output objects and then store those bytes in
+    the cache. When it comes time to re-emit those bytes, they are wrapped
+    in a ``wireprototypes.encodedresponse`` instance to tell the output
+    layer that they are pre-encoded.
+
+    When receiving the objects emitted by the command function, instances
+    can choose what to do with those objects. The simplest thing to do is
+    re-emit the original objects. They will be forwarded to the output
+    layer and will be processed as if the cacher did not exist.
+
+    Implementations could also choose to not emit objects - instead locally
+    buffering objects or their encoded representation. They could then emit
+    a single "coalesced" object when ``onoutputfinished()`` is called. In
+    this way, the implementation would function as a filtering layer of
+    sorts.
+
+    When caching objects, typically the encoded form of the object will
+    be stored. Keep in mind that if the original object is forwarded to
+    the output layer, it will need to be encoded there as well. For large
+    output, this redundant encoding could add overhead. Implementations
+    could wrap the encoded object data in ``wireprototypes.encodedresponse``
+    instances to avoid this overhead.
+    """
+    def __enter__():
+        """Marks the instance as active.
+
+        Should return self.
+        """
+
+    def __exit__(exctype, excvalue, exctb):
+        """Called when cacher is no longer used.
+
+        This can be used by implementations to perform cleanup actions (e.g.
+        disconnecting network sockets, aborting a partially cached response.
+        """
+
+    def adjustcachekeystate(state):
+        """Influences cache key derivation by adjusting state to derive key.
+
+        A dict defining the state used to derive the cache key is passed.
+
+        Implementations can modify this dict to record additional state that
+        is wanted to influence key derivation.
+
+        Implementations are *highly* encouraged to not modify or delete
+        existing keys.
+        """
+
+    def setcachekey(key):
+        """Record the derived cache key for this request.
+
+        Instances may mutate the key for internal usage, as desired. e.g.
+        instances may wish to prepend the repo name, introduce path
+        components for filesystem or URL addressing, etc. Behavior is up to
+        the cache.
+
+        Returns a bool indicating if the request is cacheable by this
+        instance.
+        """
+
+    def lookup():
+        """Attempt to resolve an entry in the cache.
+
+        The instance is instructed to look for the cache key that it was
+        informed about via the call to ``setcachekey()``.
+
+        If there's no cache hit or the cacher doesn't wish to use the cached
+        entry, ``None`` should be returned.
+
+        Else, a dict defining the cached result should be returned. The
+        dict may have the following keys:
+
+        objs
+           An iterable of objects that should be sent to the client. That
+           iterable of objects is expected to be what the command function
+           would return if invoked or an equivalent representation thereof.
+        """
+
+    def onobject(obj):
+        """Called when a new object is emitted from the command function.
+
+        Receives as its argument the object that was emitted from the
+        command function.
+
+        This method returns an iterator of objects to forward to the output
+        layer. The easiest implementation is a generator that just
+        ``yield obj``.
+        """
+
+    def onfinished():
+        """Called after all objects have been emitted from the command function.
+
+        Implementations should return an iterator of objects to forward to
+        the output layer.
+
+        This method can be a generator.
+        """

mercurial/wireprototypes.py

@@ -1,369 +1,370
 # Copyright 2018 Gregory Szorc <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 from __future__ import absolute_import
 
 from .node import (
     bin,
     hex,
 )
 from .i18n import _
 from .thirdparty import (
     attr,
 )
 from . import (
     error,
     util,
 )
 from .utils import (
     interfaceutil,
 )
 
 # Names of the SSH protocol implementations.
 SSHV1 = 'ssh-v1'
 # These are advertised over the wire. Increment the counters at the end
 # to reflect BC breakages.
 SSHV2 = 'exp-ssh-v2-0002'
 HTTP_WIREPROTO_V2 = 'exp-http-v2-0002'
 
 # All available wire protocol transports.
 TRANSPORTS = {
     SSHV1: {
         'transport': 'ssh',
         'version': 1,
     },
     SSHV2: {
         'transport': 'ssh',
         # TODO mark as version 2 once all commands are implemented.
         'version': 1,
     },
     'http-v1': {
         'transport': 'http',
         'version': 1,
     },
     HTTP_WIREPROTO_V2: {
         'transport': 'http',
         'version': 2,
     }
 }
 
 class bytesresponse(object):
     """A wire protocol response consisting of raw bytes."""
     def __init__(self, data):
         self.data = data
 
 class ooberror(object):
     """wireproto reply: failure of a batch of operation
 
     Something failed during a batch call. The error message is stored in
     `self.message`.
     """
     def __init__(self, message):
         self.message = message
 
 class pushres(object):
     """wireproto reply: success with simple integer return
 
     The call was successful and returned an integer contained in `self.res`.
     """
     def __init__(self, res, output):
         self.res = res
         self.output = output
 
 class pusherr(object):
     """wireproto reply: failure
 
     The call failed. The `self.res` attribute contains the error message.
     """
     def __init__(self, res, output):
         self.res = res
         self.output = output
 
 class streamres(object):
     """wireproto reply: binary stream
 
     The call was successful and the result is a stream.
 
     Accepts a generator containing chunks of data to be sent to the client.
 
     ``prefer_uncompressed`` indicates that the data is expected to be
     uncompressable and that the stream should therefore use the ``none``
     engine.
     """
     def __init__(self, gen=None, prefer_uncompressed=False):
         self.gen = gen
         self.prefer_uncompressed = prefer_uncompressed
 
 class streamreslegacy(object):
     """wireproto reply: uncompressed binary stream
 
     The call was successful and the result is a stream.
 
     Accepts a generator containing chunks of data to be sent to the client.
 
     Like ``streamres``, but sends an uncompressed data for "version 1" clients
     using the application/mercurial-0.1 media type.
     """
     def __init__(self, gen=None):
         self.gen = gen
 
 # list of nodes encoding / decoding
 def decodelist(l, sep=' '):
     if l:
         return [bin(v) for v in  l.split(sep)]
     return []
 
 def encodelist(l, sep=' '):
     try:
         return sep.join(map(hex, l))
     except TypeError:
         raise
 
 # batched call argument encoding
 
 def escapebatcharg(plain):
     return (plain
             .replace(':', ':c')
             .replace(',', ':o')
             .replace(';', ':s')
             .replace('=', ':e'))
 
 def unescapebatcharg(escaped):
     return (escaped
             .replace(':e', '=')
             .replace(':s', ';')
             .replace(':o', ',')
             .replace(':c', ':'))
 
 # mapping of options accepted by getbundle and their types
 #
 # Meant to be extended by extensions. It is extensions responsibility to ensure
 # such options are properly processed in exchange.getbundle.
 #
 # supported types are:
 #
 # :nodes: list of binary nodes
 # :csv:   list of comma-separated values
 # :scsv:  list of comma-separated values return as set
 # :plain: string with no transformation needed.
 GETBUNDLE_ARGUMENTS = {
     'heads':  'nodes',
     'bookmarks': 'boolean',
     'common': 'nodes',
     'obsmarkers': 'boolean',
     'phases': 'boolean',
     'bundlecaps': 'scsv',
     'listkeys': 'csv',
     'cg': 'boolean',
     'cbattempted': 'boolean',
     'stream': 'boolean',
 }
 
 class baseprotocolhandler(interfaceutil.Interface):
     """Abstract base class for wire protocol handlers.
 
     A wire protocol handler serves as an interface between protocol command
     handlers and the wire protocol transport layer. Protocol handlers provide
     methods to read command arguments, redirect stdio for the duration of
     the request, handle response types, etc.
     """
 
     name = interfaceutil.Attribute(
         """The name of the protocol implementation.
 
         Used for uniquely identifying the transport type.
         """)
 
     def getargs(args):
         """return the value for arguments in <args>
 
         For version 1 transports, returns a list of values in the same
         order they appear in ``args``. For version 2 transports, returns
         a dict mapping argument name to value.
         """
 
     def getprotocaps():
         """Returns the list of protocol-level capabilities of client
 
         Returns a list of capabilities as declared by the client for
         the current request (or connection for stateful protocol handlers)."""
 
     def getpayload():
         """Provide a generator for the raw payload.
 
         The caller is responsible for ensuring that the full payload is
         processed.
         """
 
     def mayberedirectstdio():
         """Context manager to possibly redirect stdio.
 
         The context manager yields a file-object like object that receives
         stdout and stderr output when the context manager is active. Or it
         yields ``None`` if no I/O redirection occurs.
 
         The intent of this context manager is to capture stdio output
         so it may be sent in the response. Some transports support streaming
         stdio to the client in real time. For these transports, stdio output
         won't be captured.
         """
 
     def client():
         """Returns a string representation of this client (as bytes)."""
 
     def addcapabilities(repo, caps):
         """Adds advertised capabilities specific to this protocol.
 
         Receives the list of capabilities collected so far.
 
         Returns a list of capabilities. The passed in argument can be returned.
         """
 
     def checkperm(perm):
         """Validate that the client has permissions to perform a request.
 
         The argument is the permission required to proceed. If the client
         doesn't have that permission, the exception should raise or abort
         in a protocol specific manner.
         """
 
 class commandentry(object):
     """Represents a declared wire protocol command."""
     def __init__(self, func, args='', transports=None,
-                 permission='push'):
+                 permission='push', cachekeyfn=None):
         self.func = func
         self.args = args
         self.transports = transports or set()
         self.permission = permission
+        self.cachekeyfn = cachekeyfn
 
     def _merge(self, func, args):
         """Merge this instance with an incoming 2-tuple.
 
         This is called when a caller using the old 2-tuple API attempts
         to replace an instance. The incoming values are merged with
         data not captured by the 2-tuple and a new instance containing
         the union of the two objects is returned.
         """
         return commandentry(func, args=args, transports=set(self.transports),
                             permission=self.permission)
 
     # Old code treats instances as 2-tuples. So expose that interface.
     def __iter__(self):
         yield self.func
         yield self.args
 
     def __getitem__(self, i):
         if i == 0:
             return self.func
         elif i == 1:
             return self.args
         else:
             raise IndexError('can only access elements 0 and 1')
 
 class commanddict(dict):
     """Container for registered wire protocol commands.
 
     It behaves like a dict. But __setitem__ is overwritten to allow silent
     coercion of values from 2-tuples for API compatibility.
     """
     def __setitem__(self, k, v):
         if isinstance(v, commandentry):
             pass
         # Cast 2-tuples to commandentry instances.
         elif isinstance(v, tuple):
             if len(v) != 2:
                 raise ValueError('command tuples must have exactly 2 elements')
 
             # It is common for extensions to wrap wire protocol commands via
             # e.g. ``wireproto.commands[x] = (newfn, args)``. Because callers
             # doing this aren't aware of the new API that uses objects to store
             # command entries, we automatically merge old state with new.
             if k in self:
                 v = self[k]._merge(v[0], v[1])
             else:
                 # Use default values from @wireprotocommand.
                 v = commandentry(v[0], args=v[1],
                                  transports=set(TRANSPORTS),
                                  permission='push')
         else:
             raise ValueError('command entries must be commandentry instances '
                              'or 2-tuples')
 
         return super(commanddict, self).__setitem__(k, v)
 
     def commandavailable(self, command, proto):
         """Determine if a command is available for the requested protocol."""
         assert proto.name in TRANSPORTS
 
         entry = self.get(command)
 
         if not entry:
             return False
 
         if proto.name not in entry.transports:
             return False
 
         return True
 
 def supportedcompengines(ui, role):
     """Obtain the list of supported compression engines for a request."""
     assert role in (util.CLIENTROLE, util.SERVERROLE)
 
     compengines = util.compengines.supportedwireengines(role)
 
     # Allow config to override default list and ordering.
     if role == util.SERVERROLE:
         configengines = ui.configlist('server', 'compressionengines')
         config = 'server.compressionengines'
     else:
         # This is currently implemented mainly to facilitate testing. In most
         # cases, the server should be in charge of choosing a compression engine
         # because a server has the most to lose from a sub-optimal choice. (e.g.
         # CPU DoS due to an expensive engine or a network DoS due to poor
         # compression ratio).
         configengines = ui.configlist('experimental',
                                       'clientcompressionengines')
         config = 'experimental.clientcompressionengines'
 
     # No explicit config. Filter out the ones that aren't supposed to be
     # advertised and return default ordering.
     if not configengines:
         attr = 'serverpriority' if role == util.SERVERROLE else 'clientpriority'
         return [e for e in compengines
                 if getattr(e.wireprotosupport(), attr) > 0]
 
     # If compression engines are listed in the config, assume there is a good
     # reason for it (like server operators wanting to achieve specific
     # performance characteristics). So fail fast if the config references
     # unusable compression engines.
     validnames = set(e.name() for e in compengines)
     invalidnames = set(e for e in configengines if e not in validnames)
     if invalidnames:
         raise error.Abort(_('invalid compression engine defined in %s: %s') %
                           (config, ', '.join(sorted(invalidnames))))
 
     compengines = [e for e in compengines if e.name() in configengines]
     compengines = sorted(compengines,
                          key=lambda e: configengines.index(e.name()))
 
     if not compengines:
         raise error.Abort(_('%s config option does not specify any known '
                             'compression engines') % config,
                           hint=_('usable compression engines: %s') %
                           ', '.sorted(validnames))
 
     return compengines
 
 @attr.s
 class encodedresponse(object):
     """Represents response data that is already content encoded.
 
     Wire protocol version 2 only.
 
     Commands typically emit Python objects that are encoded and sent over the
     wire. If commands emit an object of this type, the encoding step is bypassed
     and the content from this object is used instead.
     """
     data = attr.ib()

mercurial/wireprotov2server.py

@@ -1,970 +1,1129
 # Copyright 21 May 2005 - (c) 2005 Jake Edge <[e-mail]>
 # Copyright 2005-2007 Matt Mackall <[e-mail]>
 #
 # This software may be used and distributed according to the terms of the
 # GNU General Public License version 2 or any later version.
 
 from __future__ import absolute_import
 
 import contextlib
+import hashlib
 
 from .i18n import _
 from .node import (
     hex,
     nullid,
 )
 from . import (
     discovery,
     encoding,
     error,
     narrowspec,
     pycompat,
     streamclone,
     util,
     wireprotoframing,
     wireprototypes,
 )
 from .utils import (
+    cborutil,
     interfaceutil,
     stringutil,
 )
 
 FRAMINGTYPE = b'application/mercurial-exp-framing-0005'
 
 HTTP_WIREPROTO_V2 = wireprototypes.HTTP_WIREPROTO_V2
 
 COMMANDS = wireprototypes.commanddict()
 
+# Value inserted into cache key computation function. Change the value to
+# force new cache keys for every command request. This should be done when
+# there is a change to how caching works, etc.
+GLOBAL_CACHE_VERSION = 1
+
 def handlehttpv2request(rctx, req, res, checkperm, urlparts):
     from .hgweb import common as hgwebcommon
 
     # URL space looks like: <permissions>/<command>, where <permission> can
     # be ``ro`` or ``rw`` to signal read-only or read-write, respectively.
 
     # Root URL does nothing meaningful... yet.
     if not urlparts:
         res.status = b'200 OK'
         res.headers[b'Content-Type'] = b'text/plain'
         res.setbodybytes(_('HTTP version 2 API handler'))
         return
 
     if len(urlparts) == 1:
         res.status = b'404 Not Found'
         res.headers[b'Content-Type'] = b'text/plain'
         res.setbodybytes(_('do not know how to process %s\n') %
                          req.dispatchpath)
         return
 
     permission, command = urlparts[0:2]
 
     if permission not in (b'ro', b'rw'):
         res.status = b'404 Not Found'
         res.headers[b'Content-Type'] = b'text/plain'
         res.setbodybytes(_('unknown permission: %s') % permission)
         return
 
     if req.method != 'POST':
         res.status = b'405 Method Not Allowed'
         res.headers[b'Allow'] = b'POST'
         res.setbodybytes(_('commands require POST requests'))
         return
 
     # At some point we'll want to use our own API instead of recycling the
     # behavior of version 1 of the wire protocol...
     # TODO return reasonable responses - not responses that overload the
     # HTTP status line message for error reporting.
     try:
         checkperm(rctx, req, 'pull' if permission == b'ro' else 'push')
     except hgwebcommon.ErrorResponse as e:
         res.status = hgwebcommon.statusmessage(e.code, pycompat.bytestr(e))
         for k, v in e.headers:
             res.headers[k] = v
         res.setbodybytes('permission denied')
         return
 
     # We have a special endpoint to reflect the request back at the client.
     if command == b'debugreflect':
         _processhttpv2reflectrequest(rctx.repo.ui, rctx.repo, req, res)
         return
 
     # Extra commands that we handle that aren't really wire protocol
     # commands. Think extra hard before making this hackery available to
     # extension.
     extracommands = {'multirequest'}
 
     if command not in COMMANDS and command not in extracommands:
         res.status = b'404 Not Found'
         res.headers[b'Content-Type'] = b'text/plain'
         res.setbodybytes(_('unknown wire protocol command: %s\n') % command)
         return
 
     repo = rctx.repo
     ui = repo.ui
 
     proto = httpv2protocolhandler(req, ui)
 
     if (not COMMANDS.commandavailable(command, proto)
         and command not in extracommands):
         res.status = b'404 Not Found'
         res.headers[b'Content-Type'] = b'text/plain'
         res.setbodybytes(_('invalid wire protocol command: %s') % command)
         return
 
     # TODO consider cases where proxies may add additional Accept headers.
     if req.headers.get(b'Accept') != FRAMINGTYPE:
         res.status = b'406 Not Acceptable'
         res.headers[b'Content-Type'] = b'text/plain'
         res.setbodybytes(_('client MUST specify Accept header with value: %s\n')
                            % FRAMINGTYPE)
         return
 
     if req.headers.get(b'Content-Type') != FRAMINGTYPE:
         res.status = b'415 Unsupported Media Type'
         # TODO we should send a response with appropriate media type,
         # since client does Accept it.
         res.headers[b'Content-Type'] = b'text/plain'
         res.setbodybytes(_('client MUST send Content-Type header with '
                            'value: %s\n') % FRAMINGTYPE)
         return
 
     _processhttpv2request(ui, repo, req, res, permission, command, proto)
 
 def _processhttpv2reflectrequest(ui, repo, req, res):
     """Reads unified frame protocol request and dumps out state to client.
 
     This special endpoint can be used to help debug the wire protocol.
 
     Instead of routing the request through the normal dispatch mechanism,
     we instead read all frames, decode them, and feed them into our state
     tracker. We then dump the log of all that activity back out to the
     client.
     """
     import json
 
     # Reflection APIs have a history of being abused, accidentally disclosing
     # sensitive data, etc. So we have a config knob.
     if not ui.configbool('experimental', 'web.api.debugreflect'):
         res.status = b'404 Not Found'
         res.headers[b'Content-Type'] = b'text/plain'
         res.setbodybytes(_('debugreflect service not available'))
         return
 
     # We assume we have a unified framing protocol request body.
 
     reactor = wireprotoframing.serverreactor()
     states = []
 
     while True:
         frame = wireprotoframing.readframe(req.bodyfh)
 
         if not frame:
             states.append(b'received: <no frame>')
             break
 
         states.append(b'received: %d %d %d %s' % (frame.typeid, frame.flags,
                                                   frame.requestid,
                                                   frame.payload))
 
         action, meta = reactor.onframerecv(frame)
         states.append(json.dumps((action, meta), sort_keys=True,
                                  separators=(', ', ': ')))
 
     action, meta = reactor.oninputeof()
     meta['action'] = action
     states.append(json.dumps(meta, sort_keys=True, separators=(', ',': ')))
 
     res.status = b'200 OK'
     res.headers[b'Content-Type'] = b'text/plain'
     res.setbodybytes(b'\n'.join(states))
 
 def _processhttpv2request(ui, repo, req, res, authedperm, reqcommand, proto):
     """Post-validation handler for HTTPv2 requests.
 
     Called when the HTTP request contains unified frame-based protocol
     frames for evaluation.
     """
     # TODO Some HTTP clients are full duplex and can receive data before
     # the entire request is transmitted. Figure out a way to indicate support
     # for that so we can opt into full duplex mode.
     reactor = wireprotoframing.serverreactor(deferoutput=True)
     seencommand = False
 
     outstream = reactor.makeoutputstream()
 
     while True:
         frame = wireprotoframing.readframe(req.bodyfh)
         if not frame:
             break
 
         action, meta = reactor.onframerecv(frame)
 
         if action == 'wantframe':
             # Need more data before we can do anything.
             continue
         elif action == 'runcommand':
             sentoutput = _httpv2runcommand(ui, repo, req, res, authedperm,
                                            reqcommand, reactor, outstream,
                                            meta, issubsequent=seencommand)
 
             if sentoutput:
                 return
 
             seencommand = True
 
         elif action == 'error':
             # TODO define proper error mechanism.
             res.status = b'200 OK'
             res.headers[b'Content-Type'] = b'text/plain'
             res.setbodybytes(meta['message'] + b'\n')
             return
         else:
             raise error.ProgrammingError(
                 'unhandled action from frame processor: %s' % action)
 
     action, meta = reactor.oninputeof()
     if action == 'sendframes':
         # We assume we haven't started sending the response yet. If we're
         # wrong, the response type will raise an exception.
         res.status = b'200 OK'
         res.headers[b'Content-Type'] = FRAMINGTYPE
         res.setbodygen(meta['framegen'])
     elif action == 'noop':
         pass
     else:
         raise error.ProgrammingError('unhandled action from frame processor: %s'
                                      % action)
 
 def _httpv2runcommand(ui, repo, req, res, authedperm, reqcommand, reactor,
                       outstream, command, issubsequent):
     """Dispatch a wire protocol command made from HTTPv2 requests.
 
     The authenticated permission (``authedperm``) along with the original
     command from the URL (``reqcommand``) are passed in.
     """
     # We already validated that the session has permissions to perform the
     # actions in ``authedperm``. In the unified frame protocol, the canonical
     # command to run is expressed in a frame. However, the URL also requested
     # to run a specific command. We need to be careful that the command we
     # run doesn't have permissions requirements greater than what was granted
     # by ``authedperm``.
     #
     # Our rule for this is we only allow one command per HTTP request and
     # that command must match the command in the URL. However, we make
     # an exception for the ``multirequest`` URL. This URL is allowed to
     # execute multiple commands. We double check permissions of each command
     # as it is invoked to ensure there is no privilege escalation.
     # TODO consider allowing multiple commands to regular command URLs
     # iff each command is the same.
 
     proto = httpv2protocolhandler(req, ui, args=command['args'])
 
     if reqcommand == b'multirequest':
         if not COMMANDS.commandavailable(command['command'], proto):
             # TODO proper error mechanism
             res.status = b'200 OK'
             res.headers[b'Content-Type'] = b'text/plain'
             res.setbodybytes(_('wire protocol command not available: %s') %
                              command['command'])
             return True
 
         # TODO don't use assert here, since it may be elided by -O.
         assert authedperm in (b'ro', b'rw')
         wirecommand = COMMANDS[command['command']]
         assert wirecommand.permission in ('push', 'pull')
 
         if authedperm == b'ro' and wirecommand.permission != 'pull':
             # TODO proper error mechanism
             res.status = b'403 Forbidden'
             res.headers[b'Content-Type'] = b'text/plain'
             res.setbodybytes(_('insufficient permissions to execute '
                                'command: %s') % command['command'])
             return True
 
         # TODO should we also call checkperm() here? Maybe not if we're going
         # to overhaul that API. The granted scope from the URL check should
         # be good enough.
 
     else:
         # Don't allow multiple commands outside of ``multirequest`` URL.
         if issubsequent:
             # TODO proper error mechanism
             res.status = b'200 OK'
             res.headers[b'Content-Type'] = b'text/plain'
             res.setbodybytes(_('multiple commands cannot be issued to this '
                                'URL'))
             return True
 
         if reqcommand != command['command']:
             # TODO define proper error mechanism
             res.status = b'200 OK'
             res.headers[b'Content-Type'] = b'text/plain'
             res.setbodybytes(_('command in frame must match command in URL'))
             return True
 
     res.status = b'200 OK'
     res.headers[b'Content-Type'] = FRAMINGTYPE
 
     try:
         objs = dispatch(repo, proto, command['command'])
 
         action, meta = reactor.oncommandresponsereadyobjects(
             outstream, command['requestid'], objs)
 
     except error.WireprotoCommandError as e:
         action, meta = reactor.oncommanderror(
             outstream, command['requestid'], e.message, e.messageargs)
 
     except Exception as e:
         action, meta = reactor.onservererror(
             outstream, command['requestid'],
             _('exception when invoking command: %s') %
             stringutil.forcebytestr(e))
 
     if action == 'sendframes':
         res.setbodygen(meta['framegen'])
         return True
     elif action == 'noop':
         return False
     else:
         raise error.ProgrammingError('unhandled event from reactor: %s' %
                                      action)
 
 def getdispatchrepo(repo, proto, command):
     return repo.filtered('served')
 
 def dispatch(repo, proto, command):
+    """Run a wire protocol command.
+
+    Returns an iterable of objects that will be sent to the client.
+    """
     repo = getdispatchrepo(repo, proto, command)
 
-    func, spec = COMMANDS[command]
+    entry = COMMANDS[command]
+    func = entry.func
+    spec = entry.args
+
     args = proto.getargs(spec)
 
-    return func(repo, proto, **pycompat.strkwargs(args))
+    # There is some duplicate boilerplate code here for calling the command and
+    # emitting objects. It is either that or a lot of indented code that looks
+    # like a pyramid (since there are a lot of code paths that result in not
+    # using the cacher).
+    callcommand = lambda: func(repo, proto, **pycompat.strkwargs(args))
+
+    # Request is not cacheable. Don't bother instantiating a cacher.
+    if not entry.cachekeyfn:
+        for o in callcommand():
+            yield o
+        return
+
+    cacher = makeresponsecacher(repo, proto, command, args,
+                                cborutil.streamencode)
+
+    # But we have no cacher. Do default handling.
+    if not cacher:
+        for o in callcommand():
+            yield o
+        return
+
+    with cacher:
+        cachekey = entry.cachekeyfn(repo, proto, cacher, **args)
+
+        # No cache key or the cacher doesn't like it. Do default handling.
+        if cachekey is None or not cacher.setcachekey(cachekey):
+            for o in callcommand():
+                yield o
+            return
+
+        # Serve it from the cache, if possible.
+        cached = cacher.lookup()
+
+        if cached:
+            for o in cached['objs']:
+                yield o
+            return
+
+        # Else call the command and feed its output into the cacher, allowing
+        # the cacher to buffer/mutate objects as it desires.
+        for o in callcommand():
+            for o in cacher.onobject(o):
+                yield o
+
+        for o in cacher.onfinished():
+            yield o
 
 @interfaceutil.implementer(wireprototypes.baseprotocolhandler)
 class httpv2protocolhandler(object):
     def __init__(self, req, ui, args=None):
         self._req = req
         self._ui = ui
         self._args = args
 
     @property
     def name(self):
         return HTTP_WIREPROTO_V2
 
     def getargs(self, args):
         # First look for args that were passed but aren't registered on this
         # command.
         extra = set(self._args) - set(args)
         if extra:
             raise error.WireprotoCommandError(
                 'unsupported argument to command: %s' %
                 ', '.join(sorted(extra)))
 
         # And look for required arguments that are missing.
         missing = {a for a in args if args[a]['required']} - set(self._args)
 
         if missing:
             raise error.WireprotoCommandError(
                 'missing required arguments: %s' % ', '.join(sorted(missing)))
 
         # Now derive the arguments to pass to the command, taking into
         # account the arguments specified by the client.
         data = {}
         for k, meta in sorted(args.items()):
             # This argument wasn't passed by the client.
             if k not in self._args:
                 data[k] = meta['default']()
                 continue
 
             v = self._args[k]
 
             # Sets may be expressed as lists. Silently normalize.
             if meta['type'] == 'set' and isinstance(v, list):
                 v = set(v)
 
             # TODO consider more/stronger type validation.
 
             data[k] = v
 
         return data
 
     def getprotocaps(self):
         # Protocol capabilities are currently not implemented for HTTP V2.
         return set()
 
     def getpayload(self):
         raise NotImplementedError
 
     @contextlib.contextmanager
     def mayberedirectstdio(self):
         raise NotImplementedError
 
     def client(self):
         raise NotImplementedError
 
     def addcapabilities(self, repo, caps):
         return caps
 
     def checkperm(self, perm):
         raise NotImplementedError
 
 def httpv2apidescriptor(req, repo):
     proto = httpv2protocolhandler(req, repo.ui)
 
     return _capabilitiesv2(repo, proto)
 
 def _capabilitiesv2(repo, proto):
     """Obtain the set of capabilities for version 2 transports.
 
     These capabilities are distinct from the capabilities for version 1
     transports.
     """
     compression = []
     for engine in wireprototypes.supportedcompengines(repo.ui, util.SERVERROLE):
         compression.append({
             b'name': engine.wireprotosupport().name,
         })
 
     caps = {
         'commands': {},
         'compression': compression,
         'framingmediatypes': [FRAMINGTYPE],
         'pathfilterprefixes': set(narrowspec.VALID_PREFIXES),
     }
 
     for command, entry in COMMANDS.items():
         args = {}
 
         for arg, meta in entry.args.items():
             args[arg] = {
                 # TODO should this be a normalized type using CBOR's
                 # terminology?
                 b'type': meta['type'],
                 b'required': meta['required'],
             }
 
             if not meta['required']:
                 args[arg][b'default'] = meta['default']()
 
             if meta['validvalues']:
                 args[arg][b'validvalues'] = meta['validvalues']
 
         caps['commands'][command] = {
             'args': args,
             'permissions': [entry.permission],
         }
 
     if streamclone.allowservergeneration(repo):
         caps['rawrepoformats'] = sorted(repo.requirements &
                                         repo.supportedformats)
 
     return proto.addcapabilities(repo, caps)
 
-def wireprotocommand(name, args=None, permission='push'):
+def wireprotocommand(name, args=None, permission='push', cachekeyfn=None):
     """Decorator to declare a wire protocol command.
 
     ``name`` is the name of the wire protocol command being provided.
 
     ``args`` is a dict defining arguments accepted by the command. Keys are
     the argument name. Values are dicts with the following keys:
 
        ``type``
           The argument data type. Must be one of the following string
           literals: ``bytes``, ``int``, ``list``, ``dict``, ``set``,
           or ``bool``.
 
        ``default``
           A callable returning the default value for this argument. If not
           specified, ``None`` will be the default value.
 
        ``example``
           An example value for this argument.
 
        ``validvalues``
           Set of recognized values for this argument.
 
     ``permission`` defines the permission type needed to run this command.
     Can be ``push`` or ``pull``. These roughly map to read-write and read-only,
     respectively. Default is to assume command requires ``push`` permissions
     because otherwise commands not declaring their permissions could modify
     a repository that is supposed to be read-only.
 
+    ``cachekeyfn`` defines an optional callable that can derive the
+    cache key for this request.
+
     Wire protocol commands are generators of objects to be serialized and
     sent to the client.
 
     If a command raises an uncaught exception, this will be translated into
     a command error.
+
+    All commands can opt in to being cacheable by defining a function
+    (``cachekeyfn``) that is called to derive a cache key. This function
+    receives the same arguments as the command itself plus a ``cacher``
+    argument containing the active cacher for the request and returns a bytes
+    containing the key in a cache the response to this command may be cached
+    under.
     """
     transports = {k for k, v in wireprototypes.TRANSPORTS.items()
                   if v['version'] == 2}
 
     if permission not in ('push', 'pull'):
         raise error.ProgrammingError('invalid wire protocol permission; '
                                      'got %s; expected "push" or "pull"' %
                                      permission)
 
     if args is None:
         args = {}
 
     if not isinstance(args, dict):
         raise error.ProgrammingError('arguments for version 2 commands '
                                      'must be declared as dicts')
 
     for arg, meta in args.items():
         if arg == '*':
             raise error.ProgrammingError('* argument name not allowed on '
                                          'version 2 commands')
 
         if not isinstance(meta, dict):
             raise error.ProgrammingError('arguments for version 2 commands '
                                          'must declare metadata as a dict')
 
         if 'type' not in meta:
             raise error.ProgrammingError('%s argument for command %s does not '
                                          'declare type field' % (arg, name))
 
         if meta['type'] not in ('bytes', 'int', 'list', 'dict', 'set', 'bool'):
             raise error.ProgrammingError('%s argument for command %s has '
                                          'illegal type: %s' % (arg, name,
                                                                meta['type']))
 
         if 'example' not in meta:
             raise error.ProgrammingError('%s argument for command %s does not '
                                          'declare example field' % (arg, name))
 
         meta['required'] = 'default' not in meta
 
         meta.setdefault('default', lambda: None)
         meta.setdefault('validvalues', None)
 
     def register(func):
         if name in COMMANDS:
             raise error.ProgrammingError('%s command already registered '
                                          'for version 2' % name)
 
         COMMANDS[name] = wireprototypes.commandentry(
-            func, args=args, transports=transports, permission=permission)
+            func, args=args, transports=transports, permission=permission,
+            cachekeyfn=cachekeyfn)
 
         return func
 
     return register
 
+def makecommandcachekeyfn(command, localversion=None, allargs=False):
+    """Construct a cache key derivation function with common features.
+
+    By default, the cache key is a hash of:
+
+    * The command name.
+    * A global cache version number.
+    * A local cache version number (passed via ``localversion``).
+    * All the arguments passed to the command.
+    * The media type used.
+    * Wire protocol version string.
+    * The repository path.
+    """
+    if not allargs:
+        raise error.ProgrammingError('only allargs=True is currently supported')
+
+    if localversion is None:
+        raise error.ProgrammingError('must set localversion argument value')
+
+    def cachekeyfn(repo, proto, cacher, **args):
+        spec = COMMANDS[command]
+
+        # Commands that mutate the repo can not be cached.
+        if spec.permission == 'push':
+            return None
+
+        # TODO config option to disable caching.
+
+        # Our key derivation strategy is to construct a data structure
+        # holding everything that could influence cacheability and to hash
+        # the CBOR representation of that. Using CBOR seems like it might
+        # be overkill. However, simpler hashing mechanisms are prone to
+        # duplicate input issues. e.g. if you just concatenate two values,
+        # "foo"+"bar" is identical to "fo"+"obar". Using CBOR provides
+        # "padding" between values and prevents these problems.
+
+        # Seed the hash with various data.
+        state = {
+            # To invalidate all cache keys.
+            b'globalversion': GLOBAL_CACHE_VERSION,
+            # More granular cache key invalidation.
+            b'localversion': localversion,
+            # Cache keys are segmented by command.
+            b'command': pycompat.sysbytes(command),
+            # Throw in the media type and API version strings so changes
+            # to exchange semantics invalid cache.
+            b'mediatype': FRAMINGTYPE,
+            b'version': HTTP_WIREPROTO_V2,
+            # So same requests for different repos don't share cache keys.
+            b'repo': repo.root,
+        }
+
+        # The arguments passed to us will have already been normalized.
+        # Default values will be set, etc. This is important because it
+        # means that it doesn't matter if clients send an explicit argument
+        # or rely on the default value: it will all normalize to the same
+        # set of arguments on the server and therefore the same cache key.
+        #
+        # Arguments by their very nature must support being encoded to CBOR.
+        # And the CBOR encoder is deterministic. So we hash the arguments
+        # by feeding the CBOR of their representation into the hasher.
+        if allargs:
+            state[b'args'] = pycompat.byteskwargs(args)
+
+        cacher.adjustcachekeystate(state)
+
+        hasher = hashlib.sha1()
+        for chunk in cborutil.streamencode(state):
+            hasher.update(chunk)
+
+        return pycompat.sysbytes(hasher.hexdigest())
+
+    return cachekeyfn
+
+def makeresponsecacher(repo, proto, command, args, objencoderfn):
+    """Construct a cacher for a cacheable command.
+
+    Returns an ``iwireprotocolcommandcacher`` instance.
+
+    Extensions can monkeypatch this function to provide custom caching
+    backends.
+    """
+    return None
+
 @wireprotocommand('branchmap', permission='pull')
 def branchmapv2(repo, proto):
     yield {encoding.fromlocal(k): v
            for k, v in repo.branchmap().iteritems()}
 
 @wireprotocommand('capabilities', permission='pull')
 def capabilitiesv2(repo, proto):
     yield _capabilitiesv2(repo, proto)
 
 @wireprotocommand(
     'changesetdata',
     args={
         'noderange': {
             'type': 'list',
             'default': lambda: None,
             'example': [[b'0123456...'], [b'abcdef...']],
         },
         'nodes': {
             'type': 'list',
             'default': lambda: None,
             'example': [b'0123456...'],
         },
         'nodesdepth': {
             'type': 'int',
             'default': lambda: None,
             'example': 10,
         },
         'fields': {
             'type': 'set',
             'default': set,
             'example': {b'parents', b'revision'},
             'validvalues': {b'bookmarks', b'parents', b'phase', b'revision'},
         },
     },
     permission='pull')
 def changesetdata(repo, proto, noderange, nodes, nodesdepth, fields):
     # TODO look for unknown fields and abort when they can't be serviced.
     # This could probably be validated by dispatcher using validvalues.
 
     if noderange is None and nodes is None:
         raise error.WireprotoCommandError(
             'noderange or nodes must be defined')
 
     if nodesdepth is not None and nodes is None:
         raise error.WireprotoCommandError(
             'nodesdepth requires the nodes argument')
 
     if noderange is not None:
         if len(noderange) != 2:
             raise error.WireprotoCommandError(
                 'noderange must consist of 2 elements')
 
         if not noderange[1]:
             raise error.WireprotoCommandError(
                 'heads in noderange request cannot be empty')
 
     cl = repo.changelog
     hasnode = cl.hasnode
 
     seen = set()
     outgoing = []
 
     if nodes is not None:
         outgoing = [n for n in nodes if hasnode(n)]
 
         if nodesdepth:
             outgoing = [cl.node(r) for r in
                         repo.revs(b'ancestors(%ln, %d)', outgoing,
                                   nodesdepth - 1)]
 
         seen |= set(outgoing)
 
     if noderange is not None:
         if noderange[0]:
             common = [n for n in noderange[0] if hasnode(n)]
         else:
             common = [nullid]
 
         for n in discovery.outgoing(repo, common, noderange[1]).missing:
             if n not in seen:
                 outgoing.append(n)
             # Don't need to add to seen here because this is the final
             # source of nodes and there should be no duplicates in this
             # list.
 
     seen.clear()
     publishing = repo.publishing()
 
     if outgoing:
         repo.hook('preoutgoing', throw=True, source='serve')
 
     yield {
         b'totalitems': len(outgoing),
     }
 
     # The phases of nodes already transferred to the client may have changed
     # since the client last requested data. We send phase-only records
     # for these revisions, if requested.
     if b'phase' in fields and noderange is not None:
         # TODO skip nodes whose phase will be reflected by a node in the
         # outgoing set. This is purely an optimization to reduce data
         # size.
         for node in noderange[0]:
             yield {
                 b'node': node,
                 b'phase': b'public' if publishing else repo[node].phasestr()
             }
 
     nodebookmarks = {}
     for mark, node in repo._bookmarks.items():
         nodebookmarks.setdefault(node, set()).add(mark)
 
     # It is already topologically sorted by revision number.
     for node in outgoing:
         d = {
             b'node': node,
         }
 
         if b'parents' in fields:
             d[b'parents'] = cl.parents(node)
 
         if b'phase' in fields:
             if publishing:
                 d[b'phase'] = b'public'
             else:
                 ctx = repo[node]
                 d[b'phase'] = ctx.phasestr()
 
         if b'bookmarks' in fields and node in nodebookmarks:
             d[b'bookmarks'] = sorted(nodebookmarks[node])
             del nodebookmarks[node]
 
         followingmeta = []
         followingdata = []
 
         if b'revision' in fields:
             revisiondata = cl.revision(node, raw=True)
             followingmeta.append((b'revision', len(revisiondata)))
             followingdata.append(revisiondata)
 
         # TODO make it possible for extensions to wrap a function or register
         # a handler to service custom fields.
 
         if followingmeta:
             d[b'fieldsfollowing'] = followingmeta
 
         yield d
 
         for extra in followingdata:
             yield extra
 
     # If requested, send bookmarks from nodes that didn't have revision
     # data sent so receiver is aware of any bookmark updates.
     if b'bookmarks' in fields:
         for node, marks in sorted(nodebookmarks.iteritems()):
             yield {
                 b'node': node,
                 b'bookmarks': sorted(marks),
             }
 
 class FileAccessError(Exception):
     """Represents an error accessing a specific file."""
 
     def __init__(self, path, msg, args):
         self.path = path
         self.msg = msg
         self.args = args
 
 def getfilestore(repo, proto, path):
     """Obtain a file storage object for use with wire protocol.
 
     Exists as a standalone function so extensions can monkeypatch to add
     access control.
     """
     # This seems to work even if the file doesn't exist. So catch
     # "empty" files and return an error.
     fl = repo.file(path)
 
     if not len(fl):
         raise FileAccessError(path, 'unknown file: %s', (path,))
 
     return fl
 
 @wireprotocommand(
     'filedata',
     args={
         'haveparents': {
             'type': 'bool',
             'default': lambda: False,
             'example': True,
         },
         'nodes': {
             'type': 'list',
             'example': [b'0123456...'],
         },
         'fields': {
             'type': 'set',
             'default': set,
             'example': {b'parents', b'revision'},
             'validvalues': {b'parents', b'revision'},
         },
         'path': {
             'type': 'bytes',
             'example': b'foo.txt',
         }
     },
-    permission='pull')
+    permission='pull',
+    # TODO censoring a file revision won't invalidate the cache.
+    # Figure out a way to take censoring into account when deriving
+    # the cache key.
+    cachekeyfn=makecommandcachekeyfn('filedata', 1, allargs=True))
 def filedata(repo, proto, haveparents, nodes, fields, path):
     try:
         # Extensions may wish to access the protocol handler.
         store = getfilestore(repo, proto, path)
     except FileAccessError as e:
         raise error.WireprotoCommandError(e.msg, e.args)
 
     # Validate requested nodes.
     for node in nodes:
         try:
             store.rev(node)
         except error.LookupError:
             raise error.WireprotoCommandError('unknown file node: %s',
                                               (hex(node),))
 
     revisions = store.emitrevisions(nodes,
                                     revisiondata=b'revision' in fields,
                                     assumehaveparentrevisions=haveparents)
 
     yield {
         b'totalitems': len(nodes),
     }
 
     for revision in revisions:
         d = {
             b'node': revision.node,
         }
 
         if b'parents' in fields:
             d[b'parents'] = [revision.p1node, revision.p2node]
 
         followingmeta = []
         followingdata = []
 
         if b'revision' in fields:
             if revision.revision is not None:
                 followingmeta.append((b'revision', len(revision.revision)))
                 followingdata.append(revision.revision)
             else:
                 d[b'deltabasenode'] = revision.basenode
                 followingmeta.append((b'delta', len(revision.delta)))
                 followingdata.append(revision.delta)
 
         if followingmeta:
             d[b'fieldsfollowing'] = followingmeta
 
         yield d
 
         for extra in followingdata:
             yield extra
 
 @wireprotocommand(
     'heads',
     args={
         'publiconly': {
             'type': 'bool',
             'default': lambda: False,
             'example': False,
         },
     },
     permission='pull')
 def headsv2(repo, proto, publiconly):
     if publiconly:
         repo = repo.filtered('immutable')
 
     yield repo.heads()
 
 @wireprotocommand(
     'known',
     args={
         'nodes': {
             'type': 'list',
             'default': list,
             'example': [b'deadbeef'],
         },
     },
     permission='pull')
 def knownv2(repo, proto, nodes):
     result = b''.join(b'1' if n else b'0' for n in repo.known(nodes))
     yield result
 
 @wireprotocommand(
     'listkeys',
     args={
         'namespace': {
             'type': 'bytes',
             'example': b'ns',
         },
     },
     permission='pull')
 def listkeysv2(repo, proto, namespace):
     keys = repo.listkeys(encoding.tolocal(namespace))
     keys = {encoding.fromlocal(k): encoding.fromlocal(v)
             for k, v in keys.iteritems()}
 
     yield keys
 
 @wireprotocommand(
     'lookup',
     args={
         'key': {
             'type': 'bytes',
             'example': b'foo',
         },
     },
     permission='pull')
 def lookupv2(repo, proto, key):
     key = encoding.tolocal(key)
 
     # TODO handle exception.
     node = repo.lookup(key)
 
     yield node
 
 @wireprotocommand(
     'manifestdata',
     args={
         'nodes': {
             'type': 'list',
             'example': [b'0123456...'],
         },
         'haveparents': {
             'type': 'bool',
             'default': lambda: False,
             'example': True,
         },
         'fields': {
             'type': 'set',
             'default': set,
             'example': {b'parents', b'revision'},
             'validvalues': {b'parents', b'revision'},
         },
         'tree': {
             'type': 'bytes',
             'example': b'',
         },
     },
-    permission='pull')
+    permission='pull',
+    cachekeyfn=makecommandcachekeyfn('manifestdata', 1, allargs=True))
 def manifestdata(repo, proto, haveparents, nodes, fields, tree):
     store = repo.manifestlog.getstorage(tree)
 
     # Validate the node is known and abort on unknown revisions.
     for node in nodes:
         try:
             store.rev(node)
         except error.LookupError:
             raise error.WireprotoCommandError(
                 'unknown node: %s', (node,))
 
     revisions = store.emitrevisions(nodes,
                                     revisiondata=b'revision' in fields,
                                     assumehaveparentrevisions=haveparents)
 
     yield {
         b'totalitems': len(nodes),
     }
 
     for revision in revisions:
         d = {
             b'node': revision.node,
         }
 
         if b'parents' in fields:
             d[b'parents'] = [revision.p1node, revision.p2node]
 
         followingmeta = []
         followingdata = []
 
         if b'revision' in fields:
             if revision.revision is not None:
                 followingmeta.append((b'revision', len(revision.revision)))
                 followingdata.append(revision.revision)
             else:
                 d[b'deltabasenode'] = revision.basenode
                 followingmeta.append((b'delta', len(revision.delta)))
                 followingdata.append(revision.delta)
 
         if followingmeta:
             d[b'fieldsfollowing'] = followingmeta
 
         yield d
 
         for extra in followingdata:
             yield extra
 
 @wireprotocommand(
     'pushkey',
     args={
         'namespace': {
             'type': 'bytes',
             'example': b'ns',
         },
         'key': {
             'type': 'bytes',
             'example': b'key',
         },
         'old': {
             'type': 'bytes',
             'example': b'old',
         },
         'new': {
             'type': 'bytes',
             'example': 'new',
         },
     },
     permission='push')
 def pushkeyv2(repo, proto, namespace, key, old, new):
     # TODO handle ui output redirection
     yield repo.pushkey(encoding.tolocal(namespace),
                        encoding.tolocal(key),
                        encoding.tolocal(old),
                        encoding.tolocal(new))