streamclone: also stream caches to the client

When stream clone is used over bundle2, relevant cache files are also streamed.
This is expected to be a massive performance win for clone since no important
cache will have to be recomputed.

Some performance numbers:

(All times are wall-clock times in seconds, 2 attempts per case.)

# Mozilla-Central

## Clone over ssh over lan
V1 streaming: 234.3 239.6
V2 streaming: 248.4 243.7

## Clone over ssh over Internet
V1 streaming: 175.5 110.9
V2 streaming: 109.1 111.0

## Clone over HTTP over lan
V1 streaming: 105.3 105.6
V2 streaming: 112.7 111.4

## Clone over HTTP over internet
V1 streaming: 105.6 114.6
V2 streaming: 226.7 225.9

## Hg tags
V1 streaming (no cache): 1.084 1.071
V2 streaming (cache):    0.312 0.325

## Hg branches
V1 streaming (no cache):   14.047 14.148
V2 streaming (with cache):  0.312  0.333

# Pypy

## Clone over ssh over internet
V1 streaming: 29.4 30.1
V2 streaming: 31.2 30.1

## Clone over http over internet
V1 streaming: 29.7 29.7
V2 streaming: 75.2 72.9

(since ssh and lan are not affected, there seems to be an issue with how we
read/write the http stream on connection with latency, unrelated to the format)

## Hg tags
V1 streaming (no cache):   1.752 1.664
V2 streaming (with cache): 0.274 0.260

## Hg branches
V1 streaming (no cache):   4.469 4.728
V2 streaming (with cache): 0.318 0.321

# Private repository:
    * 500K revision revisions
    * 11K topological heads
    * 28K branch heads

## hg tags
no cache:   1543.332
with cache:    4.900

## hg branches
no cache:   91.828
with cache:  2.955

mercurial/streamclone.py

@@ -11,10 +11,12 b' import contextlib'
 import os
 import struct
 import tempfile
+import warnings
 
 from .i18n import _
 from . import (
     branchmap,
+    cacheutil,
     error,
     phases,
     store,
@@ -435,6 +437,10 b' class streamcloneapplier(object):'
 _fileappend = 0 # append only file
 _filefull = 1   # full snapshot file
 
+# Source of the file
+_srcstore = 's' # store (svfs)
+_srccache = 'c' # cache (cache)
+
 # This is it's own function so extensions can override it.
 def _walkstreamfullstorefiles(repo):
     """list snapshot file from the store"""
@@ -443,12 +449,12 b' def _walkstreamfullstorefiles(repo):'
         fnames.append('phaseroots')
     return fnames
 
-def _filterfull(entry, copy, vfs):
+def _filterfull(entry, copy, vfsmap):
     """actually copy the snapshot files"""
-    name, ftype, data = entry
+    src, name, ftype, data = entry
     if ftype != _filefull:
         return entry
-    return (name, ftype, copy(vfs.join(name)))
+    return (src, name, ftype, copy(vfsmap[src].join(name)))
 
 @contextlib.contextmanager
 def maketempcopies():
@@ -466,19 +472,33 b' def maketempcopies():'
         for tmp in files:
             util.tryunlink(tmp)
 
+def _makemap(repo):
+    """make a (src -> vfs) map for the repo"""
+    vfsmap = {
+        _srcstore: repo.svfs,
+        _srccache: repo.cachevfs,
+    }
+    # we keep repo.vfs out of the on purpose, ther are too many danger there
+    # (eg: .hg/hgrc)
+    assert repo.vfs not in vfsmap.values()
+
+    return vfsmap
+
 def _emit(repo, entries, totalfilesize):
     """actually emit the stream bundle"""
-    vfs = repo.svfs
+    vfsmap = _makemap(repo)
     progress = repo.ui.progress
     progress(_('bundle'), 0, total=totalfilesize, unit=_('bytes'))
     with maketempcopies() as copy:
         try:
             # copy is delayed until we are in the try
-            entries = [_filterfull(e, copy, vfs) for e in entries]
+            entries = [_filterfull(e, copy, vfsmap) for e in entries]
             yield None # this release the lock on the repository
             seen = 0
 
-            for name, ftype, data in entries:
+            for src, name, ftype, data in entries:
+                vfs = vfsmap[src]
+                yield src
                 yield util.uvarintencode(len(name))
                 if ftype == _fileappend:
                     fp = vfs(name)
@@ -507,10 +527,11 b' def generatev2(repo):'
     """Emit content for version 2 of a streaming clone.
 
     the data stream consists the following entries:
-    1) A varint containing the length of the filename
-    2) A varint containing the length of file data
-    3) N bytes containing the filename (the internal, store-agnostic form)
-    4) N bytes containing the file data
+    1) A char representing the file destination (eg: store or cache)
+    2) A varint containing the length of the filename
+    3) A varint containing the length of file data
+    4) N bytes containing the filename (the internal, store-agnostic form)
+    5) N bytes containing the file data
 
     Returns a 3-tuple of (file count, file size, data iterator).
     """
@@ -523,12 +544,16 b' def generatev2(repo):'
         repo.ui.debug('scanning\n')
         for name, ename, size in _walkstreamfiles(repo):
             if size:
-                entries.append((name, _fileappend, size))
+                entries.append((_srcstore, name, _fileappend, size))
                 totalfilesize += size
         for name in _walkstreamfullstorefiles(repo):
             if repo.svfs.exists(name):
                 totalfilesize += repo.svfs.lstat(name).st_size
-                entries.append((name, _filefull, None))
+                entries.append((_srcstore, name, _filefull, None))
+        for name in cacheutil.cachetocopy(repo):
+            if repo.cachevfs.exists(name):
+                totalfilesize += repo.cachevfs.lstat(name).st_size
+                entries.append((_srccache, name, _filefull, None))
 
         chunks = _emit(repo, entries, totalfilesize)
         first = next(chunks)
@@ -536,6 +561,16 b' def generatev2(repo):'
 
     return len(entries), totalfilesize, chunks
 
[e-mail]
+def nested(*ctxs):
+    with warnings.catch_warnings():
+        # For some reason, Python decided 'nested' was deprecated without
+        # replacement. They officially advertised for filtering the deprecation
+        # warning for people who actually need the feature.
+        warnings.filterwarnings("ignore",category=DeprecationWarning)
+        with contextlib.nested(*ctxs):
+            yield
+
 def consumev2(repo, fp, filecount, filesize):
     """Apply the contents from a version 2 streaming clone.
 
@@ -552,19 +587,23 b' def consumev2(repo, fp, filecount, files'
 
         progress(_('clone'), handledbytes, total=filesize, unit=_('bytes'))
 
-        vfs = repo.svfs
+        vfsmap = _makemap(repo)
 
         with repo.transaction('clone'):
-            with vfs.backgroundclosing(repo.ui):
+            ctxs = (vfs.backgroundclosing(repo.ui)
+                    for vfs in vfsmap.values())
+            with nested(*ctxs):
                 for i in range(filecount):
+                    src = fp.read(1)
+                    vfs = vfsmap[src]
                     namelen = util.uvarintdecodestream(fp)
                     datalen = util.uvarintdecodestream(fp)
 
                     name = fp.read(namelen)
 
                     if repo.ui.debugflag:
-                        repo.ui.debug('adding %s (%s)\n' %
-                                      (name, util.bytecount(datalen)))
+                        repo.ui.debug('adding [%s] %s (%s)\n' %
+                                      (src, name, util.bytecount(datalen)))
 
                     with vfs(name, 'w') as ofp:
                         for chunk in util.filechunkiter(fp, limit=datalen):

tests/test-clone-uncompressed.t

@@ -38,8 +38,13 b' Basic clone'
 #if stream-bundle2
   $ hg clone --stream -U http://localhost:$HGPORT clone1
   streaming all changes
-  1027 files to transfer, 96.3 KB of data
-  transferred 96.3 KB in * seconds (* */sec) (glob)
+  1030 files to transfer, 96.4 KB of data
+  transferred 96.4 KB in * seconds (* */sec) (glob)
+
+  $ ls -1 clone1/.hg/cache
+  branch2-served
+  rbc-names-v1
+  rbc-revs-v1
 #endif
 
 --uncompressed is an alias to --stream
@@ -55,8 +60,8 b' Basic clone'
 #if stream-bundle2
   $ hg clone --uncompressed -U http://localhost:$HGPORT clone1-uncompressed
   streaming all changes
-  1027 files to transfer, 96.3 KB of data
-  transferred 96.3 KB in * seconds (* */sec) (glob)
+  1030 files to transfer, 96.4 KB of data
+  transferred 96.4 KB in * seconds (* */sec) (glob)
 #endif
 
 Clone with background file closing enabled
@@ -95,10 +100,11 b' Clone with background file closing enabl'
   bundle2-input-bundle: with-transaction
   bundle2-input-part: "stream" (params: 4 mandatory) supported
   applying stream bundle
-  1027 files to transfer, 96.3 KB of data
+  1030 files to transfer, 96.4 KB of data
+  starting 4 threads for background file closing
   starting 4 threads for background file closing
-  transferred 96.3 KB in * seconds (* */sec) (glob)
-  bundle2-input-part: total payload size 110887
+  transferred 96.4 KB in * seconds (* */sec) (glob)
+  bundle2-input-part: total payload size 112077
   bundle2-input-part: "listkeys" (params: 1 mandatory) supported
   bundle2-input-bundle: 1 parts total
   checking for updated bookmarks
@@ -136,8 +142,8 b' Streaming of secrets can be overridden b'
 #if stream-bundle2
   $ hg clone --stream -U http://localhost:$HGPORT secret-allowed
   streaming all changes
-  1027 files to transfer, 96.3 KB of data
-  transferred 96.3 KB in * seconds (* */sec) (glob)
+  1030 files to transfer, 96.4 KB of data
+  transferred 96.4 KB in * seconds (* */sec) (glob)
 #endif
 
   $ killdaemons.py
@@ -253,8 +259,8 b' clone it'
 #if stream-bundle2
   $ hg clone --stream http://localhost:$HGPORT with-bookmarks
   streaming all changes
-  1027 files to transfer, 96.3 KB of data
-  transferred 96.3 KB in * seconds (* */sec) (glob)
+  1033 files to transfer, 96.6 KB of data
+  transferred 96.6 KB in * seconds (* */sec) (glob)
   updating to branch default
   1025 files updated, 0 files merged, 0 files removed, 0 files unresolved
 #endif
@@ -283,8 +289,8 b' Clone as publishing'
 #if stream-bundle2
   $ hg clone --stream http://localhost:$HGPORT phase-publish
   streaming all changes
-  1027 files to transfer, 96.3 KB of data
-  transferred 96.3 KB in * seconds (* */sec) (glob)
+  1033 files to transfer, 96.6 KB of data
+  transferred 96.6 KB in * seconds (* */sec) (glob)
   updating to branch default
   1025 files updated, 0 files merged, 0 files removed, 0 files unresolved
 #endif
@@ -318,8 +324,8 b' Clone as non publishing'
 #if stream-bundle2
   $ hg clone --stream http://localhost:$HGPORT phase-no-publish
   streaming all changes
-  1028 files to transfer, 96.4 KB of data
-  transferred 96.4 KB in * seconds (* */sec) (glob)
+  1034 files to transfer, 96.7 KB of data
+  transferred 96.7 KB in * seconds (* */sec) (glob)
   updating to branch default
   1025 files updated, 0 files merged, 0 files removed, 0 files unresolved
   $ hg -R phase-no-publish phase -r 'all()'