wireproto: implement batching on peer executor interface

This is a bit more complicated than non-batch requests because we
need to buffer sends until the last request arrives *and* we need
to support resolving futures as data arrives from the remote.

In a classical concurrent.futures executor model, the future
"starts" as soon as it is submitted. However, we have nothing to
start until the last command is submitted.

If we did nothing, calling result() would deadlock, since the future
hasn't "started." So in the case where we queue the command, we return
a special future type whose result() will trigger sendcommands().
This eliminates the deadlock potential. It also serves as a check
against callers who may be calling result() prematurely, as it will
prevent any subsequent callcommands() from working. This behavior
is slightly annoying and a bit restrictive. But it's the world
that half duplex connections forces on us.

In order to support streaming responses, we were previously using
a generator. But with a futures-based API, we're using futures
and not generators. So in order to get streaming, we need a
background thread to read data from the server.

The approach taken in this patch is to leverage the ThreadPoolExecutor
from concurrent.futures for managing a background thread. We create
an executor and future that resolves when all response data is
processed (or an error occurs). When exiting the context manager,
we wait on that background reading before returning.

I was hoping we could manually spin up a threading.Thread and this
would be simple. But I ran into a few deadlocks when implementing.
After looking at the source code to concurrent.futures, I figured
it would just be easier to use a ThreadPoolExecutor than implement
all the code needed to manually manage a thread.

To prove this works, a use of the batch API in discovery has been
updated.

Differential Revision: https://phab.mercurial-scm.org/D3269

mercurial/setdiscovery.py

@@ -1,267 +1,270 b''
 # setdiscovery.py - improved discovery of common nodeset for mercurial
 #
 # Copyright 2010 Benoit Boissinot <[e-mail]>
 # and Peter Arrenbrecht <[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.
 """
 Algorithm works in the following way. You have two repository: local and
 remote. They both contains a DAG of changelists.
 
 The goal of the discovery protocol is to find one set of node *common*,
 the set of nodes shared by local and remote.
 
 One of the issue with the original protocol was latency, it could
 potentially require lots of roundtrips to discover that the local repo was a
 subset of remote (which is a very common case, you usually have few changes
 compared to upstream, while upstream probably had lots of development).
 
 The new protocol only requires one interface for the remote repo: `known()`,
 which given a set of changelists tells you if they are present in the DAG.
 
 The algorithm then works as follow:
 
  - We will be using three sets, `common`, `missing`, `unknown`. Originally
  all nodes are in `unknown`.
  - Take a sample from `unknown`, call `remote.known(sample)`
    - For each node that remote knows, move it and all its ancestors to `common`
    - For each node that remote doesn't know, move it and all its descendants
    to `missing`
  - Iterate until `unknown` is empty
 
 There are a couple optimizations, first is instead of starting with a random
 sample of missing, start by sending all heads, in the case where the local
 repo is a subset, you computed the answer in one round trip.
 
 Then you can do something similar to the bisecting strategy used when
 finding faulty changesets. Instead of random samples, you can try picking
 nodes that will maximize the number of nodes that will be
 classified with it (since all ancestors or descendants will be marked as well).
 """
 
 from __future__ import absolute_import
 
 import collections
 import random
 
 from .i18n import _
 from .node import (
     nullid,
     nullrev,
 )
 from . import (
     dagutil,
     error,
     util,
 )
 
 def _updatesample(dag, nodes, sample, quicksamplesize=0):
     """update an existing sample to match the expected size
 
     The sample is updated with nodes exponentially distant from each head of the
     <nodes> set. (H~1, H~2, H~4, H~8, etc).
 
     If a target size is specified, the sampling will stop once this size is
     reached. Otherwise sampling will happen until roots of the <nodes> set are
     reached.
 
     :dag: a dag object from dagutil
     :nodes:  set of nodes we want to discover (if None, assume the whole dag)
     :sample: a sample to update
     :quicksamplesize: optional target size of the sample"""
     # if nodes is empty we scan the entire graph
     if nodes:
         heads = dag.headsetofconnecteds(nodes)
     else:
         heads = dag.heads()
     dist = {}
     visit = collections.deque(heads)
     seen = set()
     factor = 1
     while visit:
         curr = visit.popleft()
         if curr in seen:
             continue
         d = dist.setdefault(curr, 1)
         if d > factor:
             factor *= 2
         if d == factor:
             sample.add(curr)
             if quicksamplesize and (len(sample) >= quicksamplesize):
                 return
         seen.add(curr)
         for p in dag.parents(curr):
             if not nodes or p in nodes:
                 dist.setdefault(p, d + 1)
                 visit.append(p)
 
 def _takequicksample(dag, nodes, size):
     """takes a quick sample of size <size>
 
     It is meant for initial sampling and focuses on querying heads and close
     ancestors of heads.
 
     :dag: a dag object
     :nodes: set of nodes to discover
     :size: the maximum size of the sample"""
     sample = dag.headsetofconnecteds(nodes)
     if len(sample) >= size:
         return _limitsample(sample, size)
     _updatesample(dag, None, sample, quicksamplesize=size)
     return sample
 
 def _takefullsample(dag, nodes, size):
     sample = dag.headsetofconnecteds(nodes)
     # update from heads
     _updatesample(dag, nodes, sample)
     # update from roots
     _updatesample(dag.inverse(), nodes, sample)
     assert sample
     sample = _limitsample(sample, size)
     if len(sample) < size:
         more = size - len(sample)
         sample.update(random.sample(list(nodes - sample), more))
     return sample
 
 def _limitsample(sample, desiredlen):
     """return a random subset of sample of at most desiredlen item"""
     if len(sample) > desiredlen:
         sample = set(random.sample(sample, desiredlen))
     return sample
 
 def findcommonheads(ui, local, remote,
                     initialsamplesize=100,
                     fullsamplesize=200,
                     abortwhenunrelated=True,
                     ancestorsof=None):
     '''Return a tuple (common, anyincoming, remoteheads) used to identify
     missing nodes from or in remote.
     '''
     start = util.timer()
 
     roundtrips = 0
     cl = local.changelog
     localsubset = None
     if ancestorsof is not None:
         rev = local.changelog.rev
         localsubset = [rev(n) for n in ancestorsof]
     dag = dagutil.revlogdag(cl, localsubset=localsubset)
 
     # early exit if we know all the specified remote heads already
     ui.debug("query 1; heads\n")
     roundtrips += 1
     ownheads = dag.heads()
     sample = _limitsample(ownheads, initialsamplesize)
     # indices between sample and externalized version must match
     sample = list(sample)
-    batch = remote.iterbatch()
-    batch.heads()
-    batch.known(dag.externalizeall(sample))
-    batch.submit()
-    srvheadhashes, yesno = batch.results()
+
+    with remote.commandexecutor() as e:
+        fheads = e.callcommand('heads', {})
+        fknown = e.callcommand('known', {
+            'nodes': dag.externalizeall(sample),
+        })
+
+    srvheadhashes, yesno = fheads.result(), fknown.result()
 
     if cl.tip() == nullid:
         if srvheadhashes != [nullid]:
             return [nullid], True, srvheadhashes
         return [nullid], False, []
 
     # start actual discovery (we note this before the next "if" for
     # compatibility reasons)
     ui.status(_("searching for changes\n"))
 
     srvheads = dag.internalizeall(srvheadhashes, filterunknown=True)
     if len(srvheads) == len(srvheadhashes):
         ui.debug("all remote heads known locally\n")
         return (srvheadhashes, False, srvheadhashes,)
 
     if len(sample) == len(ownheads) and all(yesno):
         ui.note(_("all local heads known remotely\n"))
         ownheadhashes = dag.externalizeall(ownheads)
         return (ownheadhashes, True, srvheadhashes,)
 
     # full blown discovery
 
     # own nodes I know we both know
     # treat remote heads (and maybe own heads) as a first implicit sample
     # response
     common = cl.incrementalmissingrevs(srvheads)
     commoninsample = set(n for i, n in enumerate(sample) if yesno[i])
     common.addbases(commoninsample)
     # own nodes where I don't know if remote knows them
     undecided = set(common.missingancestors(ownheads))
     # own nodes I know remote lacks
     missing = set()
 
     full = False
     while undecided:
 
         if sample:
             missinginsample = [n for i, n in enumerate(sample) if not yesno[i]]
             missing.update(dag.descendantset(missinginsample, missing))
 
             undecided.difference_update(missing)
 
         if not undecided:
             break
 
         if full or common.hasbases():
             if full:
                 ui.note(_("sampling from both directions\n"))
             else:
                 ui.debug("taking initial sample\n")
             samplefunc = _takefullsample
             targetsize = fullsamplesize
         else:
             # use even cheaper initial sample
             ui.debug("taking quick initial sample\n")
             samplefunc = _takequicksample
             targetsize = initialsamplesize
         if len(undecided) < targetsize:
             sample = list(undecided)
         else:
             sample = samplefunc(dag, undecided, targetsize)
 
         roundtrips += 1
         ui.progress(_('searching'), roundtrips, unit=_('queries'))
         ui.debug("query %i; still undecided: %i, sample size is: %i\n"
                  % (roundtrips, len(undecided), len(sample)))
         # indices between sample and externalized version must match
         sample = list(sample)
 
         with remote.commandexecutor() as e:
             yesno = e.callcommand('known', {
                 'nodes': dag.externalizeall(sample),
             }).result()
 
         full = True
 
         if sample:
             commoninsample = set(n for i, n in enumerate(sample) if yesno[i])
             common.addbases(commoninsample)
             common.removeancestorsfrom(undecided)
 
     # heads(common) == heads(common.bases) since common represents common.bases
     # and all its ancestors
     result = dag.headsetofconnecteds(common.bases)
     # common.bases can include nullrev, but our contract requires us to not
     # return any heads in that case, so discard that
     result.discard(nullrev)
     elapsed = util.timer() - start
     ui.progress(_('searching'), None)
     ui.debug("%d total queries in %.4fs\n" % (roundtrips, elapsed))
     msg = ('found %d common and %d unknown server heads,'
            ' %d roundtrips in %.4fs\n')
     missing = set(result) - set(srvheads)
     ui.log('discovery', msg, len(result), len(missing), roundtrips,
            elapsed)
 
     if not result and srvheadhashes != [nullid]:
         if abortwhenunrelated:
             raise error.Abort(_("repository is unrelated"))
         else:
             ui.warn(_("warning: repository is unrelated\n"))
         return ({nullid}, True, srvheadhashes,)
 
     anyincoming = (srvheadhashes != [nullid])
     return dag.externalizeall(result), anyincoming, srvheadhashes

mercurial/wireprotov1peer.py

@@ -1,576 +1,708 b''
 # wireprotov1peer.py - Client-side functionality for wire protocol version 1.
 #
 # Copyright 2005-2010 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 hashlib
 import sys
+import weakref
 
 from .i18n import _
 from .node import (
     bin,
 )
 from .thirdparty.zope import (
     interface as zi,
 )
 from . import (
     bundle2,
     changegroup as changegroupmod,
     encoding,
     error,
     pushkey as pushkeymod,
     pycompat,
     repository,
     util,
     wireprototypes,
 )
 
 urlreq = util.urlreq
 
 def batchable(f):
     '''annotation for batchable methods
 
     Such methods must implement a coroutine as follows:
 
     @batchable
     def sample(self, one, two=None):
         # Build list of encoded arguments suitable for your wire protocol:
         encargs = [('one', encode(one),), ('two', encode(two),)]
         # Create future for injection of encoded result:
         encresref = future()
         # Return encoded arguments and future:
         yield encargs, encresref
         # Assuming the future to be filled with the result from the batched
         # request now. Decode it:
         yield decode(encresref.value)
 
     The decorator returns a function which wraps this coroutine as a plain
     method, but adds the original method as an attribute called "batchable",
     which is used by remotebatch to split the call into separate encoding and
     decoding phases.
     '''
     def plain(*args, **opts):
         batchable = f(*args, **opts)
         encargsorres, encresref = next(batchable)
         if not encresref:
             return encargsorres # a local result in this case
         self = args[0]
         cmd = pycompat.bytesurl(f.__name__)  # ensure cmd is ascii bytestr
         encresref.set(self._submitone(cmd, encargsorres))
         return next(batchable)
     setattr(plain, 'batchable', f)
     return plain
 
 class future(object):
     '''placeholder for a value to be set later'''
     def set(self, value):
         if util.safehasattr(self, 'value'):
             raise error.RepoError("future is already set")
         self.value = value
 
 class batcher(object):
     '''base class for batches of commands submittable in a single request
 
     All methods invoked on instances of this class are simply queued and
     return a a future for the result. Once you call submit(), all the queued
     calls are performed and the results set in their respective futures.
     '''
     def __init__(self):
         self.calls = []
     def __getattr__(self, name):
         def call(*args, **opts):
             resref = future()
             # Please don't invent non-ascii method names, or you will
             # give core hg a very sad time.
             self.calls.append((name.encode('ascii'), args, opts, resref,))
             return resref
         return call
     def submit(self):
         raise NotImplementedError()
 
 class iterbatcher(batcher):
 
     def submit(self):
         raise NotImplementedError()
 
     def results(self):
         raise NotImplementedError()
 
 class remoteiterbatcher(iterbatcher):
     def __init__(self, remote):
         super(remoteiterbatcher, self).__init__()
         self._remote = remote
 
     def __getattr__(self, name):
         # Validate this method is batchable, since submit() only supports
         # batchable methods.
         fn = getattr(self._remote, name)
         if not getattr(fn, 'batchable', None):
             raise error.ProgrammingError('Attempted to batch a non-batchable '
                                          'call to %r' % name)
 
         return super(remoteiterbatcher, self).__getattr__(name)
 
     def submit(self):
         """Break the batch request into many patch calls and pipeline them.
 
         This is mostly valuable over http where request sizes can be
         limited, but can be used in other places as well.
         """
         # 2-tuple of (command, arguments) that represents what will be
         # sent over the wire.
         requests = []
 
         # 4-tuple of (command, final future, @batchable generator, remote
         # future).
         results = []
 
         for command, args, opts, finalfuture in self.calls:
             mtd = getattr(self._remote, command)
             batchable = mtd.batchable(mtd.__self__, *args, **opts)
 
             commandargs, fremote = next(batchable)
             assert fremote
             requests.append((command, commandargs))
             results.append((command, finalfuture, batchable, fremote))
 
         if requests:
             self._resultiter = self._remote._submitbatch(requests)
 
         self._results = results
 
     def results(self):
         for command, finalfuture, batchable, remotefuture in self._results:
             # Get the raw result, set it in the remote future, feed it
             # back into the @batchable generator so it can be decoded, and
             # set the result on the final future to this value.
             remoteresult = next(self._resultiter)
             remotefuture.set(remoteresult)
             finalfuture.set(next(batchable))
 
             # Verify our @batchable generators only emit 2 values.
             try:
                 next(batchable)
             except StopIteration:
                 pass
             else:
                 raise error.ProgrammingError('%s @batchable generator emitted '
                                              'unexpected value count' % command)
 
             yield finalfuture.value
 
 def encodebatchcmds(req):
     """Return a ``cmds`` argument value for the ``batch`` command."""
     escapearg = wireprototypes.escapebatcharg
 
     cmds = []
     for op, argsdict in req:
         # Old servers didn't properly unescape argument names. So prevent
         # the sending of argument names that may not be decoded properly by
         # servers.
         assert all(escapearg(k) == k for k in argsdict)
 
         args = ','.join('%s=%s' % (escapearg(k), escapearg(v))
                         for k, v in argsdict.iteritems())
         cmds.append('%s %s' % (op, args))
 
     return ';'.join(cmds)
 
+class unsentfuture(pycompat.futures.Future):
+    """A Future variation to represent an unsent command.
+
+    Because we buffer commands and don't submit them immediately, calling
+    ``result()`` on an unsent future could deadlock. Futures for buffered
+    commands are represented by this type, which wraps ``result()`` to
+    call ``sendcommands()``.
+    """
+
+    def result(self, timeout=None):
+        if self.done():
+            return pycompat.futures.Future.result(self, timeout)
+
+        self._peerexecutor.sendcommands()
+
+        # This looks like it will infinitely recurse. However,
+        # sendcommands() should modify __class__. This call serves as a check
+        # on that.
+        return self.result(timeout)
+
 @zi.implementer(repository.ipeercommandexecutor)
 class peerexecutor(object):
     def __init__(self, peer):
         self._peer = peer
         self._sent = False
         self._closed = False
         self._calls = []
+        self._futures = weakref.WeakSet()
+        self._responseexecutor = None
+        self._responsef = None
 
     def __enter__(self):
         return self
 
     def __exit__(self, exctype, excvalee, exctb):
         self.close()
 
     def callcommand(self, command, args):
         if self._sent:
             raise error.ProgrammingError('callcommand() cannot be used '
                                          'after commands are sent')
 
         if self._closed:
             raise error.ProgrammingError('callcommand() cannot be used '
                                          'after close()')
 
         # Commands are dispatched through methods on the peer.
         fn = getattr(self._peer, pycompat.sysstr(command), None)
 
         if not fn:
             raise error.ProgrammingError(
                 'cannot call command %s: method of same name not available '
                 'on peer' % command)
 
         # Commands are either batchable or they aren't. If a command
         # isn't batchable, we send it immediately because the executor
         # can no longer accept new commands after a non-batchable command.
-        # If a command is batchable, we queue it for later.
+        # If a command is batchable, we queue it for later. But we have
+        # to account for the case of a non-batchable command arriving after
+        # a batchable one and refuse to service it.
+
+        def addcall():
+            f = pycompat.futures.Future()
+            self._futures.add(f)
+            self._calls.append((command, args, fn, f))
+            return f
 
         if getattr(fn, 'batchable', False):
-            pass
+            f = addcall()
+
+            # But since we don't issue it immediately, we wrap its result()
+            # to trigger sending so we avoid deadlocks.
+            f.__class__ = unsentfuture
+            f._peerexecutor = self
         else:
             if self._calls:
                 raise error.ProgrammingError(
                     '%s is not batchable and cannot be called on a command '
                     'executor along with other commands' % command)
 
-        # We don't support batching yet. So resolve it immediately.
-        f = pycompat.futures.Future()
-        self._calls.append((command, args, fn, f))
-        self.sendcommands()
+            f = addcall()
+
+            # Non-batchable commands can never coexist with another command
+            # in this executor. So send the command immediately.
+            self.sendcommands()
+
         return f
 
     def sendcommands(self):
         if self._sent:
             return
 
         if not self._calls:
             return
 
         self._sent = True
 
+        # Unhack any future types so caller seens a clean type and to break
+        # cycle between us and futures.
+        for f in self._futures:
+            if isinstance(f, unsentfuture):
+                f.__class__ = pycompat.futures.Future
+                f._peerexecutor = None
+
         calls = self._calls
         # Mainly to destroy references to futures.
         self._calls = None
 
+        # Simple case of a single command. We call it synchronously.
         if len(calls) == 1:
             command, args, fn, f = calls[0]
 
             # Future was cancelled. Ignore it.
             if not f.set_running_or_notify_cancel():
                 return
 
             try:
                 result = fn(**pycompat.strkwargs(args))
             except Exception:
                 f.set_exception_info(*sys.exc_info()[1:])
             else:
                 f.set_result(result)
 
             return
 
-        raise error.ProgrammingError('support for multiple commands not '
-                                     'yet implemented')
+        # Batch commands are a bit harder. First, we have to deal with the
+        # @batchable coroutine. That's a bit annoying. Furthermore, we also
+        # need to preserve streaming. i.e. it should be possible for the
+        # futures to resolve as data is coming in off the wire without having
+        # to wait for the final byte of the final response. We do this by
+        # spinning up a thread to read the responses.
+
+        requests = []
+        states = []
+
+        for command, args, fn, f in calls:
+            # Future was cancelled. Ignore it.
+            if not f.set_running_or_notify_cancel():
+                continue
+
+            try:
+                batchable = fn.batchable(fn.__self__,
+                                         **pycompat.strkwargs(args))
+            except Exception:
+                f.set_exception_info(*sys.exc_info()[1:])
+                return
+
+            # Encoded arguments and future holding remote result.
+            try:
+                encodedargs, fremote = next(batchable)
+            except Exception:
+                f.set_exception_info(*sys.exc_info()[1:])
+                return
+
+            requests.append((command, encodedargs))
+            states.append((command, f, batchable, fremote))
+
+        if not requests:
+            return
+
+        # This will emit responses in order they were executed.
+        wireresults = self._peer._submitbatch(requests)
+
+        # The use of a thread pool executor here is a bit weird for something
+        # that only spins up a single thread. However, thread management is
+        # hard and it is easy to encounter race conditions, deadlocks, etc.
+        # concurrent.futures already solves these problems and its thread pool
+        # executor has minimal overhead. So we use it.
+        self._responseexecutor = pycompat.futures.ThreadPoolExecutor(1)
+        self._responsef = self._responseexecutor.submit(self._readbatchresponse,
+                                                        states, wireresults)
 
     def close(self):
         self.sendcommands()
 
+        if self._closed:
+            return
+
         self._closed = True
 
+        if not self._responsef:
+            return
+
+        # We need to wait on our in-flight response and then shut down the
+        # executor once we have a result.
+        try:
+            self._responsef.result()
+        finally:
+            self._responseexecutor.shutdown(wait=True)
+            self._responsef = None
+            self._responseexecutor = None
+
+            # If any of our futures are still in progress, mark them as
+            # errored. Otherwise a result() could wait indefinitely.
+            for f in self._futures:
+                if not f.done():
+                    f.set_exception(error.ResponseError(
+                        _('unfulfilled batch command response')))
+
+            self._futures = None
+
+    def _readbatchresponse(self, states, wireresults):
+        # Executes in a thread to read data off the wire.
+
+        for command, f, batchable, fremote in states:
+            # Grab raw result off the wire and teach the internal future
+            # about it.
+            remoteresult = next(wireresults)
+            fremote.set(remoteresult)
+
+            # And ask the coroutine to decode that value.
+            try:
+                result = next(batchable)
+            except Exception:
+                f.set_exception_info(*sys.exc_info()[1:])
+            else:
+                f.set_result(result)
+
 class wirepeer(repository.legacypeer):
     """Client-side interface for communicating with a peer repository.
 
     Methods commonly call wire protocol commands of the same name.
 
     See also httppeer.py and sshpeer.py for protocol-specific
     implementations of this interface.
     """
     def commandexecutor(self):
         return peerexecutor(self)
 
     # Begin of ipeercommands interface.
 
     def iterbatch(self):
         return remoteiterbatcher(self)
 
     @batchable
     def lookup(self, key):
         self.requirecap('lookup', _('look up remote revision'))
         f = future()
         yield {'key': encoding.fromlocal(key)}, f
         d = f.value
         success, data = d[:-1].split(" ", 1)
         if int(success):
             yield bin(data)
         else:
             self._abort(error.RepoError(data))
 
     @batchable
     def heads(self):
         f = future()
         yield {}, f
         d = f.value
         try:
             yield wireprototypes.decodelist(d[:-1])
         except ValueError:
             self._abort(error.ResponseError(_("unexpected response:"), d))
 
     @batchable
     def known(self, nodes):
         f = future()
         yield {'nodes': wireprototypes.encodelist(nodes)}, f
         d = f.value
         try:
             yield [bool(int(b)) for b in d]
         except ValueError:
             self._abort(error.ResponseError(_("unexpected response:"), d))
 
     @batchable
     def branchmap(self):
         f = future()
         yield {}, f
         d = f.value
         try:
             branchmap = {}
             for branchpart in d.splitlines():
                 branchname, branchheads = branchpart.split(' ', 1)
                 branchname = encoding.tolocal(urlreq.unquote(branchname))
                 branchheads = wireprototypes.decodelist(branchheads)
                 branchmap[branchname] = branchheads
             yield branchmap
         except TypeError:
             self._abort(error.ResponseError(_("unexpected response:"), d))
 
     @batchable
     def listkeys(self, namespace):
         if not self.capable('pushkey'):
             yield {}, None
         f = future()
         self.ui.debug('preparing listkeys for "%s"\n' % namespace)
         yield {'namespace': encoding.fromlocal(namespace)}, f
         d = f.value
         self.ui.debug('received listkey for "%s": %i bytes\n'
                       % (namespace, len(d)))
         yield pushkeymod.decodekeys(d)
 
     @batchable
     def pushkey(self, namespace, key, old, new):
         if not self.capable('pushkey'):
             yield False, None
         f = future()
         self.ui.debug('preparing pushkey for "%s:%s"\n' % (namespace, key))
         yield {'namespace': encoding.fromlocal(namespace),
                'key': encoding.fromlocal(key),
                'old': encoding.fromlocal(old),
                'new': encoding.fromlocal(new)}, f
         d = f.value
         d, output = d.split('\n', 1)
         try:
             d = bool(int(d))
         except ValueError:
             raise error.ResponseError(
                 _('push failed (unexpected response):'), d)
         for l in output.splitlines(True):
             self.ui.status(_('remote: '), l)
         yield d
 
     def stream_out(self):
         return self._callstream('stream_out')
 
     def getbundle(self, source, **kwargs):
         kwargs = pycompat.byteskwargs(kwargs)
         self.requirecap('getbundle', _('look up remote changes'))
         opts = {}
         bundlecaps = kwargs.get('bundlecaps') or set()
         for key, value in kwargs.iteritems():
             if value is None:
                 continue
             keytype = wireprototypes.GETBUNDLE_ARGUMENTS.get(key)
             if keytype is None:
                 raise error.ProgrammingError(
                     'Unexpectedly None keytype for key %s' % key)
             elif keytype == 'nodes':
                 value = wireprototypes.encodelist(value)
             elif keytype == 'csv':
                 value = ','.join(value)
             elif keytype == 'scsv':
                 value = ','.join(sorted(value))
             elif keytype == 'boolean':
                 value = '%i' % bool(value)
             elif keytype != 'plain':
                 raise KeyError('unknown getbundle option type %s'
                                % keytype)
             opts[key] = value
         f = self._callcompressable("getbundle", **pycompat.strkwargs(opts))
         if any((cap.startswith('HG2') for cap in bundlecaps)):
             return bundle2.getunbundler(self.ui, f)
         else:
             return changegroupmod.cg1unpacker(f, 'UN')
 
     def unbundle(self, cg, heads, url):
         '''Send cg (a readable file-like object representing the
         changegroup to push, typically a chunkbuffer object) to the
         remote server as a bundle.
 
         When pushing a bundle10 stream, return an integer indicating the
         result of the push (see changegroup.apply()).
 
         When pushing a bundle20 stream, return a bundle20 stream.
 
         `url` is the url the client thinks it's pushing to, which is
         visible to hooks.
         '''
 
         if heads != ['force'] and self.capable('unbundlehash'):
             heads = wireprototypes.encodelist(
                 ['hashed', hashlib.sha1(''.join(sorted(heads))).digest()])
         else:
             heads = wireprototypes.encodelist(heads)
 
         if util.safehasattr(cg, 'deltaheader'):
             # this a bundle10, do the old style call sequence
             ret, output = self._callpush("unbundle", cg, heads=heads)
             if ret == "":
                 raise error.ResponseError(
                     _('push failed:'), output)
             try:
                 ret = int(ret)
             except ValueError:
                 raise error.ResponseError(
                     _('push failed (unexpected response):'), ret)
 
             for l in output.splitlines(True):
                 self.ui.status(_('remote: '), l)
         else:
             # bundle2 push. Send a stream, fetch a stream.
             stream = self._calltwowaystream('unbundle', cg, heads=heads)
             ret = bundle2.getunbundler(self.ui, stream)
         return ret
 
     # End of ipeercommands interface.
 
     # Begin of ipeerlegacycommands interface.
 
     def branches(self, nodes):
         n = wireprototypes.encodelist(nodes)
         d = self._call("branches", nodes=n)
         try:
             br = [tuple(wireprototypes.decodelist(b)) for b in d.splitlines()]
             return br
         except ValueError:
             self._abort(error.ResponseError(_("unexpected response:"), d))
 
     def between(self, pairs):
         batch = 8 # avoid giant requests
         r = []
         for i in xrange(0, len(pairs), batch):
             n = " ".join([wireprototypes.encodelist(p, '-')
                           for p in pairs[i:i + batch]])
             d = self._call("between", pairs=n)
             try:
                 r.extend(l and wireprototypes.decodelist(l) or []
                          for l in d.splitlines())
             except ValueError:
                 self._abort(error.ResponseError(_("unexpected response:"), d))
         return r
 
     def changegroup(self, nodes, kind):
         n = wireprototypes.encodelist(nodes)
         f = self._callcompressable("changegroup", roots=n)
         return changegroupmod.cg1unpacker(f, 'UN')
 
     def changegroupsubset(self, bases, heads, kind):
         self.requirecap('changegroupsubset', _('look up remote changes'))
         bases = wireprototypes.encodelist(bases)
         heads = wireprototypes.encodelist(heads)
         f = self._callcompressable("changegroupsubset",
                                    bases=bases, heads=heads)
         return changegroupmod.cg1unpacker(f, 'UN')
 
     # End of ipeerlegacycommands interface.
 
     def _submitbatch(self, req):
         """run batch request <req> on the server
 
         Returns an iterator of the raw responses from the server.
         """
         ui = self.ui
         if ui.debugflag and ui.configbool('devel', 'debug.peer-request'):
             ui.debug('devel-peer-request: batched-content\n')
             for op, args in req:
                 msg = 'devel-peer-request:    - %s (%d arguments)\n'
                 ui.debug(msg % (op, len(args)))
 
         unescapearg = wireprototypes.unescapebatcharg
 
         rsp = self._callstream("batch", cmds=encodebatchcmds(req))
         chunk = rsp.read(1024)
         work = [chunk]
         while chunk:
             while ';' not in chunk and chunk:
                 chunk = rsp.read(1024)
                 work.append(chunk)
             merged = ''.join(work)
             while ';' in merged:
                 one, merged = merged.split(';', 1)
                 yield unescapearg(one)
             chunk = rsp.read(1024)
             work = [merged, chunk]
         yield unescapearg(''.join(work))
 
     def _submitone(self, op, args):
         return self._call(op, **pycompat.strkwargs(args))
 
     def debugwireargs(self, one, two, three=None, four=None, five=None):
         # don't pass optional arguments left at their default value
         opts = {}
         if three is not None:
             opts[r'three'] = three
         if four is not None:
             opts[r'four'] = four
         return self._call('debugwireargs', one=one, two=two, **opts)
 
     def _call(self, cmd, **args):
         """execute <cmd> on the server
 
         The command is expected to return a simple string.
 
         returns the server reply as a string."""
         raise NotImplementedError()
 
     def _callstream(self, cmd, **args):
         """execute <cmd> on the server
 
         The command is expected to return a stream. Note that if the
         command doesn't return a stream, _callstream behaves
         differently for ssh and http peers.
 
         returns the server reply as a file like object.
         """
         raise NotImplementedError()
 
     def _callcompressable(self, cmd, **args):
         """execute <cmd> on the server
 
         The command is expected to return a stream.
 
         The stream may have been compressed in some implementations. This
         function takes care of the decompression. This is the only difference
         with _callstream.
 
         returns the server reply as a file like object.
         """
         raise NotImplementedError()
 
     def _callpush(self, cmd, fp, **args):
         """execute a <cmd> on server
 
         The command is expected to be related to a push. Push has a special
         return method.
 
         returns the server reply as a (ret, output) tuple. ret is either
         empty (error) or a stringified int.
         """
         raise NotImplementedError()
 
     def _calltwowaystream(self, cmd, fp, **args):
         """execute <cmd> on server
 
         The command will send a stream to the server and get a stream in reply.
         """
         raise NotImplementedError()
 
     def _abort(self, exception):
         """clearly abort the wire protocol connection and raise the exception
         """
         raise NotImplementedError()