wireproto: in batch queries, support queries with immediate responses

listkeys and pushkey return without querying the remote when the
remote doesn't support such queries. Before this change, the batching
code didn't handle this convention, resulting in this kind of error:

  $ hg pull ssh://user@dummy/repo1 -r tip -B a
  pulling from ssh://user@dummy/repo1
  remote: ** Unknown exception encountered with possibly-broken third-party extension disable-lookup
  remote: ** which supports versions unknown of Mercurial.
  remote: ** Please disable disable-lookup and try your action again.
  remote: ** If that fixes the bug please report it to the extension author.
  remote: ** Python 2.7.15+ (default, Oct  2 2018, 22:12:08) [GCC 8.2.0]
  remote: ** Mercurial Distributed SCM (version 4.8.1+586-ef54bd33b476+20181224)
  remote: ** Extensions loaded: disable-lookup
  remote: Traceback (most recent call last):
  remote:   File "/tmp/hgtests.i66Npc/install/bin/hg", line 43, in <module>
  remote:     dispatch.run()
  remote:   File "/tmp/hgtests.i66Npc/install/lib/python/mercurial/dispatch.py", line 99, in run
  remote:     status = dispatch(req)
  remote:   File "/tmp/hgtests.i66Npc/install/lib/python/mercurial/dispatch.py", line 225, in dispatch
  remote:     ret = _runcatch(req) or 0
  remote:   File "/tmp/hgtests.i66Npc/install/lib/python/mercurial/dispatch.py", line 376, in _runcatch
  remote:     return _callcatch(ui, _runcatchfunc)
  remote:   File "/tmp/hgtests.i66Npc/install/lib/python/mercurial/dispatch.py", line 384, in _callcatch
  remote:     return scmutil.callcatch(ui, func)
  remote:   File "/tmp/hgtests.i66Npc/install/lib/python/mercurial/scmutil.py", line 166, in callcatch
  remote:     return func()
  remote:   File "/tmp/hgtests.i66Npc/install/lib/python/mercurial/dispatch.py", line 367, in _runcatchfunc
  remote:     return _dispatch(req)
  remote:   File "/tmp/hgtests.i66Npc/install/lib/python/mercurial/dispatch.py", line 1021, in _dispatch
  remote:     cmdpats, cmdoptions)
  remote:   File "/tmp/hgtests.i66Npc/install/lib/python/mercurial/dispatch.py", line 756, in runcommand
  remote:     ret = _runcommand(ui, options, cmd, d)
  remote:   File "/tmp/hgtests.i66Npc/install/lib/python/mercurial/dispatch.py", line 1030, in _runcommand
  remote:     return cmdfunc()
  remote:   File "/tmp/hgtests.i66Npc/install/lib/python/mercurial/dispatch.py", line 1018, in <lambda>
  remote:     d = lambda: util.checksignature(func)(ui, *args, **strcmdopt)
  remote:   File "/tmp/hgtests.i66Npc/install/lib/python/mercurial/util.py", line 1670, in check
  remote:     return func(*args, **kwargs)
  remote:   File "/tmp/hgtests.i66Npc/install/lib/python/mercurial/commands.py", line 5257, in serve
  remote:     s.serve_forever()
  remote:   File "/tmp/hgtests.i66Npc/install/lib/python/mercurial/wireprotoserver.py", line 797, in serve_forever
  remote:     self.serveuntil(threading.Event())
  remote:   File "/tmp/hgtests.i66Npc/install/lib/python/mercurial/wireprotoserver.py", line 804, in serveuntil
  remote:     _runsshserver(self._ui, self._repo, self._fin, self._fout, ev)
  remote:   File "/tmp/hgtests.i66Npc/install/lib/python/mercurial/wireprotoserver.py", line 656, in _runsshserver
  remote:     rsp = wireprotov1server.dispatch(repo, proto, request)
  remote:   File "/tmp/hgtests.i66Npc/install/lib/python/mercurial/wireprotov1server.py", line 74, in dispatch
  remote:     return func(repo, proto, *args)
  remote:   File "/tmp/hgtests.i66Npc/install/lib/python/mercurial/wireprotov1server.py", line 195, in batch
  remote:     data[k] = vals[k]
  remote: KeyError: 'namespace'
  abort: unexpected response: empty string
  [255]

Differential Revision: https://phab.mercurial-scm.org/D5482

tests/test-missing-capability.t

@@ -0,0 +1,46 b''
+Checking how hg behaves when one side of a pull/push doesn't support
+some capability (because it's running an older hg version, usually).
+
+  $ hg init repo1
+  $ cd repo1
+  $ echo a > a; hg add -q a; hg commit -q -m a
+  $ hg bookmark a
+  $ hg clone -q . ../repo2
+  $ cd ../repo2
+
+  $ touch $TESTTMP/disable-lookup.py
+  $ disable_cap() {
+  >   rm -f $TESTTMP/disable-lookup.pyc # pyc caching is buggy
+  >   cat <<EOF > $TESTTMP/disable-lookup.py
+  > from mercurial import extensions, wireprotov1server
+  > def wcapabilities(orig, *args, **kwargs):
+  >   cap = orig(*args, **kwargs)
+  >   cap.remove('$1')
+  >   return cap
+  > extensions.wrapfunction(wireprotov1server, '_capabilities', wcapabilities)
+  > EOF
+  > }
+  $ cat >> ../repo1/.hg/hgrc <<EOF
+  > [extensions]
+  > disable-lookup = $TESTTMP/disable-lookup.py
+  > EOF
+  $ cat >> .hg/hgrc <<EOF
+  > [ui]
+  > ssh = "$PYTHON" "$TESTDIR/dummyssh"
+  > EOF
+
+  $ hg pull ssh://user@dummy/repo1 -r tip -B a
+  pulling from ssh://user@dummy/repo1
+  no changes found
+
+  $ disable_cap lookup
+  $ hg pull ssh://user@dummy/repo1 -r tip -B a
+  pulling from ssh://user@dummy/repo1
+  abort: other repository doesn't support revision lookup, so a rev cannot be specified.
+  [255]
+
+  $ disable_cap pushkey
+  $ hg pull ssh://user@dummy/repo1 -r tip -B a
+  pulling from ssh://user@dummy/repo1
+  abort: remote bookmark a not found!
+  [255]

mercurial/wireprotov1peer.py

@@ -1,621 +1,624 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 . import (
     bundle2,
     changegroup as changegroupmod,
     encoding,
     error,
     pushkey as pushkeymod,
     pycompat,
     repository,
     util,
     wireprototypes,
 )
 from .utils import (
     interfaceutil,
 )
 
 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)
     setattr(plain, '__name__', f.__name__)
     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
 
 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)
 
 @interfaceutil.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. 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):
             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)
 
             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:
                 pycompat.future_set_exception_info(f, sys.exc_info()[1:])
             else:
                 f.set_result(result)
 
             return
 
         # 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:
                 pycompat.future_set_exception_info(f, sys.exc_info()[1:])
                 return
 
             # Encoded arguments and future holding remote result.
             try:
-                encodedargs, fremote = next(batchable)
+                encargsorres, fremote = next(batchable)
             except Exception:
                 pycompat.future_set_exception_info(f, sys.exc_info()[1:])
                 return
 
-            requests.append((command, encodedargs))
-            states.append((command, f, batchable, fremote))
+            if not fremote:
+                f.set_result(encargsorres)
+            else:
+                requests.append((command, encargsorres))
+                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:
                 pycompat.future_set_exception_info(f, sys.exc_info()[1:])
             else:
                 f.set_result(result)
 
 @interfaceutil.implementer(repository.ipeercommands,
                            repository.ipeerlegacycommands)
 class wirepeer(repository.peer):
     """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 clonebundles(self):
         self.requirecap('clonebundles', _('clone bundles'))
         return self._call('clonebundles')
 
     @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 pycompat.iterbytestr(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, bundle, 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(bundle, 'deltaheader'):
             # this a bundle10, do the old style call sequence
             ret, output = self._callpush("unbundle", bundle, 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', bundle, 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 pycompat.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, source):
         n = wireprototypes.encodelist(nodes)
         f = self._callcompressable("changegroup", roots=n)
         return changegroupmod.cg1unpacker(f, 'UN')
 
     def changegroupsubset(self, bases, heads, source):
         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()