annotate mercurial/wireproto.py @ 25235:41965bf23295

exchange: move code for generating a streaming clone into exchange

Streaming clones are fast because they are essentially tar files.
On mozilla-central, a streaming clone only consumes ~55s CPU time
on clients as opposed to ~340s CPU time for a regular clone or gzip
bundle unbundle.

Mozilla is deploying static file "lookaside" support to our Mercurial
server. Static bundles are pre-generated and uploaded to S3. When a
clone is performed, the static file is fetched, applied, and then an
incremental pull is performed. Unfortunately, on an ideal network
connection this still takes as much wall and CPU time as a regular
clone (although it does save significant server resources).

We like the client-side wall time wins of streaming clones. But we want
to leverage S3-based pre-generated files for serving the bulk of clone
data.

This patch moves the code for producing a "stream bundle" into its
own standalone function, away from the wire protocol. This will enable
stream bundle files to be produced outside the context of the wire
protocol.

A bikeshed on whether exchange is the best module for this function
might be warranted. I selected exchange instead of changegroup because
"stream bundles" aren't changegroups (yet).

# wireproto.py - generic wire protocol support functions
#
# 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.

import urllib, tempfile, os, sys
from i18n import _
from node import bin, hex
import changegroup as changegroupmod, bundle2, pushkey as pushkeymod
import peer, error, encoding, util, store, exchange


class abstractserverproto(object):
    """abstract class that summarizes the protocol API

    Used as reference and documentation.
    """

    def getargs(self, args):
        """return the value for arguments in <args>

        returns a list of values (same order as <args>)"""
        raise NotImplementedError()

    def getfile(self, fp):
        """write the whole content of a file into a file like object

        The file is in the form::

            (<chunk-size>\n<chunk>)+0\n

        chunk size is the ascii version of the int.
        """
        raise NotImplementedError()

    def redirect(self):
        """may setup interception for stdout and stderr

        See also the `restore` method."""
        raise NotImplementedError()

    # If the `redirect` function does install interception, the `restore`
    # function MUST be defined. If interception is not used, this function
    # MUST NOT be defined.
    #
    # left commented here on purpose
    #
    #def restore(self):
    #    """reinstall previous stdout and stderr and return intercepted stdout
    #    """
    #    raise NotImplementedError()

    def groupchunks(self, cg):
        """return 4096 chunks from a changegroup object

        Some protocols may have compressed the contents."""
        raise NotImplementedError()

# abstract batching support

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()
            self.calls.append((name, args, opts, resref,))
            return resref
        return call
    def submit(self):
        pass

class localbatch(batcher):
    '''performs the queued calls directly'''
    def __init__(self, local):
        batcher.__init__(self)
        self.local = local
    def submit(self):
        for name, args, opts, resref in self.calls:
            resref.set(getattr(self.local, name)(*args, **opts))

class remotebatch(batcher):
    '''batches the queued calls; uses as few roundtrips as possible'''
    def __init__(self, remote):
        '''remote must support _submitbatch(encbatch) and
        _submitone(op, encargs)'''
        batcher.__init__(self)
        self.remote = remote
    def submit(self):
        req, rsp = [], []
        for name, args, opts, resref in self.calls:
            mtd = getattr(self.remote, name)
            batchablefn = getattr(mtd, 'batchable', None)
            if batchablefn is not None:
                batchable = batchablefn(mtd.im_self, *args, **opts)
                encargsorres, encresref = batchable.next()
                if encresref:
                    req.append((name, encargsorres,))
                    rsp.append((batchable, encresref, resref,))
                else:
                    resref.set(encargsorres)
            else:
                if req:
                    self._submitreq(req, rsp)
                    req, rsp = [], []
                resref.set(mtd(*args, **opts))
        if req:
            self._submitreq(req, rsp)
    def _submitreq(self, req, rsp):
        encresults = self.remote._submitbatch(req)
        for encres, r in zip(encresults, rsp):
            batchable, encresref, resref = r
            encresref.set(encres)
            resref.set(batchable.next())

def batchable(f):
    '''annotation for batchable methods

    Such methods must implement a coroutine as follows:

    @batchable
    def sample(self, one, two=None):
        # Handle locally computable results first:
        if not one:
            yield "a local result", 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 = batchable.next()
        if not encresref:
            return encargsorres # a local result in this case
        self = args[0]
        encresref.set(self._submitone(f.func_name, encargsorres))
        return batchable.next()
    setattr(plain, 'batchable', f)
    return plain

# list of nodes encoding / decoding

def decodelist(l, sep=' '):
    if l:
        return map(bin, l.split(sep))
    return []

def encodelist(l, sep=' '):
    try:
        return sep.join(map(hex, l))
    except TypeError:
        print l
        raise

# batched call argument encoding

def escapearg(plain):
    return (plain
            .replace(':', '::')
            .replace(',', ':,')
            .replace(';', ':;')
            .replace('=', ':='))

def unescapearg(escaped):
    return (escaped
            .replace(':=', '=')
            .replace(':;', ';')
            .replace(':,', ',')
            .replace('::', ':'))

# 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
# :plain: string with no transformation needed.
gboptsmap = {'heads':  'nodes',
             'common': 'nodes',
             'obsmarkers': 'boolean',
             'bundlecaps': 'csv',
             'listkeys': 'csv',
             'cg': 'boolean'}

# client side

class wirepeer(peer.peerrepository):

    def batch(self):
        return remotebatch(self)
    def _submitbatch(self, req):
        cmds = []
        for op, argsdict in req:
            args = ','.join('%s=%s' % p for p in argsdict.iteritems())
            cmds.append('%s %s' % (op, args))
        rsp = self._call("batch", cmds=';'.join(cmds))
        return rsp.split(';')
    def _submitone(self, op, args):
        return self._call(op, **args)

    @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)
        self._abort(error.RepoError(data))

    @batchable
    def heads(self):
        f = future()
        yield {}, f
        d = f.value
        try:
            yield decodelist(d[:-1])
        except ValueError:
            self._abort(error.ResponseError(_("unexpected response:"), d))

    @batchable
    def known(self, nodes):
        f = future()
        yield {'nodes': 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(urllib.unquote(branchname))
                branchheads = decodelist(branchheads)
                branchmap[branchname] = branchheads
            yield branchmap
        except TypeError:
            self._abort(error.ResponseError(_("unexpected response:"), d))

    def branches(self, nodes):
        n = encodelist(nodes)
        d = self._call("branches", nodes=n)
        try:
            br = [tuple(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([encodelist(p, '-') for p in pairs[i:i + batch]])
            d = self._call("between", pairs=n)
            try:
                r.extend(l and decodelist(l) or [] for l in d.splitlines())
            except ValueError:
                self._abort(error.ResponseError(_("unexpected response:"), d))
        return r

    @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

    @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
        yield pushkeymod.decodekeys(d)

    def stream_out(self):
        return self._callstream('stream_out')

    def changegroup(self, nodes, kind):
        n = 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 = encodelist(bases)
        heads = encodelist(heads)
        f = self._callcompressable("changegroupsubset",
                                   bases=bases, heads=heads)
        return changegroupmod.cg1unpacker(f, 'UN')

    def getbundle(self, source, **kwargs):
        self.requirecap('getbundle', _('look up remote changes'))
        opts = {}
        bundlecaps = kwargs.get('bundlecaps')
        if bundlecaps is not None:
            kwargs['bundlecaps'] = sorted(bundlecaps)
        else:
            bundlecaps = () # kwargs could have it to None
        for key, value in kwargs.iteritems():
            if value is None:
                continue
            keytype = gboptsmap.get(key)
            if keytype is None:
                assert False, 'unexpected'
            elif keytype == 'nodes':
                value = encodelist(value)
            elif keytype == 'csv':
                value = ','.join(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", **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, source):
        '''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 localrepository.addchangegroup()).

        When pushing a bundle20 stream, return a bundle20 stream.'''

        if heads != ['force'] and self.capable('unbundlehash'):
            heads = encodelist(['hashed',
                                util.sha1(''.join(sorted(heads))).digest()])
        else:
            heads = 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

    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['three'] = three
        if four is not None:
            opts['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.

        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()

# server side

# wire protocol command can either return a string or one of these classes.
class streamres(object):
    """wireproto reply: binary stream

    The call was successful and the result is a stream.
    Iterate on the `self.gen` attribute to retrieve chunks.
    """
    def __init__(self, gen):
        self.gen = gen

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):
        self.res = res

class pusherr(object):
    """wireproto reply: failure

    The call failed. The `self.res` attribute contains the error message.
    """
    def __init__(self, res):
        self.res = res

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

def dispatch(repo, proto, command):
    repo = repo.filtered("served")
    func, spec = commands[command]
    args = proto.getargs(spec)
    return func(repo, proto, *args)

def options(cmd, keys, others):
    opts = {}
    for k in keys:
        if k in others:
            opts[k] = others[k]
            del others[k]
    if others:
        sys.stderr.write("warning: %s ignored unexpected arguments %s\n"
                         % (cmd, ",".join(others)))
    return opts

# list of commands
commands = {}

def wireprotocommand(name, args=''):
    """decorator for wire protocol command"""
    def register(func):
        commands[name] = (func, args)
        return func
    return register

@wireprotocommand('batch', 'cmds *')
def batch(repo, proto, cmds, others):
    repo = repo.filtered("served")
    res = []
    for pair in cmds.split(';'):
        op, args = pair.split(' ', 1)
        vals = {}
        for a in args.split(','):
            if a:
                n, v = a.split('=')
                vals[n] = unescapearg(v)
        func, spec = commands[op]
        if spec:
            keys = spec.split()
            data = {}
            for k in keys:
                if k == '*':
                    star = {}
                    for key in vals.keys():
                        if key not in keys:
                            star[key] = vals[key]
                    data['*'] = star
                else:
                    data[k] = vals[k]
            result = func(repo, proto, *[data[k] for k in keys])
        else:
            result = func(repo, proto)
        if isinstance(result, ooberror):
            return result
        res.append(escapearg(result))
    return ';'.join(res)

@wireprotocommand('between', 'pairs')
def between(repo, proto, pairs):
    pairs = [decodelist(p, '-') for p in pairs.split(" ")]
    r = []
    for b in repo.between(pairs):
        r.append(encodelist(b) + "\n")
    return "".join(r)

@wireprotocommand('branchmap')
def branchmap(repo, proto):
    branchmap = repo.branchmap()
    heads = []
    for branch, nodes in branchmap.iteritems():
        branchname = urllib.quote(encoding.fromlocal(branch))
        branchnodes = encodelist(nodes)
        heads.append('%s %s' % (branchname, branchnodes))
    return '\n'.join(heads)

@wireprotocommand('branches', 'nodes')
def branches(repo, proto, nodes):
    nodes = decodelist(nodes)
    r = []
    for b in repo.branches(nodes):
        r.append(encodelist(b) + "\n")
    return "".join(r)


wireprotocaps = ['lookup', 'changegroupsubset', 'branchmap', 'pushkey',
                 'known', 'getbundle', 'unbundlehash', 'batch']

def _capabilities(repo, proto):
    """return a list of capabilities for a repo

    This function exists to allow extensions to easily wrap capabilities
    computation

    - returns a lists: easy to alter
    - change done here will be propagated to both `capabilities` and `hello`
      command without any other action needed.
    """
    # copy to prevent modification of the global list
    caps = list(wireprotocaps)
    if _allowstream(repo.ui):
        if repo.ui.configbool('server', 'preferuncompressed', False):
            caps.append('stream-preferred')
        requiredformats = repo.requirements & repo.supportedformats
        # if our local revlogs are just revlogv1, add 'stream' cap
        if not requiredformats - set(('revlogv1',)):
            caps.append('stream')
        # otherwise, add 'streamreqs' detailing our local revlog format
        else:
            caps.append('streamreqs=%s' % ','.join(requiredformats))
    if repo.ui.configbool('experimental', 'bundle2-advertise', True):
        capsblob = bundle2.encodecaps(bundle2.getrepocaps(repo))
        caps.append('bundle2=' + urllib.quote(capsblob))
    caps.append('unbundle=%s' % ','.join(changegroupmod.bundlepriority))
    caps.append('httpheader=1024')
    return caps

# If you are writing an extension and consider wrapping this function. Wrap
# `_capabilities` instead.
@wireprotocommand('capabilities')
def capabilities(repo, proto):
    return ' '.join(_capabilities(repo, proto))

@wireprotocommand('changegroup', 'roots')
def changegroup(repo, proto, roots):
    nodes = decodelist(roots)
    cg = changegroupmod.changegroup(repo, nodes, 'serve')
    return streamres(proto.groupchunks(cg))

@wireprotocommand('changegroupsubset', 'bases heads')
def changegroupsubset(repo, proto, bases, heads):
    bases = decodelist(bases)
    heads = decodelist(heads)
    cg = changegroupmod.changegroupsubset(repo, bases, heads, 'serve')
    return streamres(proto.groupchunks(cg))

@wireprotocommand('debugwireargs', 'one two *')
def debugwireargs(repo, proto, one, two, others):
    # only accept optional args from the known set
    opts = options('debugwireargs', ['three', 'four'], others)
    return repo.debugwireargs(one, two, **opts)

# List of options accepted by getbundle.
#
# Meant to be extended by extensions. It is the extension's responsibility to
# ensure such options are properly processed in exchange.getbundle.
gboptslist = ['heads', 'common', 'bundlecaps']

@wireprotocommand('getbundle', '*')
def getbundle(repo, proto, others):
    opts = options('getbundle', gboptsmap.keys(), others)
    for k, v in opts.iteritems():
        keytype = gboptsmap[k]
        if keytype == 'nodes':
            opts[k] = decodelist(v)
        elif keytype == 'csv':
            opts[k] = set(v.split(','))
        elif keytype == 'boolean':
            opts[k] = bool(v)
        elif keytype != 'plain':
            raise KeyError('unknown getbundle option type %s'
                           % keytype)
    cg = exchange.getbundle(repo, 'serve', **opts)
    return streamres(proto.groupchunks(cg))

@wireprotocommand('heads')
def heads(repo, proto):
    h = repo.heads()
    return encodelist(h) + "\n"

@wireprotocommand('hello')
def hello(repo, proto):
    '''the hello command returns a set of lines describing various
    interesting things about the server, in an RFC822-like format.
    Currently the only one defined is "capabilities", which
    consists of a line in the form:

    capabilities: space separated list of tokens
    '''
    return "capabilities: %s\n" % (capabilities(repo, proto))

@wireprotocommand('listkeys', 'namespace')
def listkeys(repo, proto, namespace):
    d = repo.listkeys(encoding.tolocal(namespace)).items()
    return pushkeymod.encodekeys(d)

@wireprotocommand('lookup', 'key')
def lookup(repo, proto, key):
    try:
        k = encoding.tolocal(key)
        c = repo[k]
        r = c.hex()
        success = 1
    except Exception, inst:
        r = str(inst)
        success = 0
    return "%s %s\n" % (success, r)

@wireprotocommand('known', 'nodes *')
def known(repo, proto, nodes, others):
    return ''.join(b and "1" or "0" for b in repo.known(decodelist(nodes)))

@wireprotocommand('pushkey', 'namespace key old new')
def pushkey(repo, proto, namespace, key, old, new):
    # compatibility with pre-1.8 clients which were accidentally
    # sending raw binary nodes rather than utf-8-encoded hex
    if len(new) == 20 and new.encode('string-escape') != new:
        # looks like it could be a binary node
        try:
            new.decode('utf-8')
            new = encoding.tolocal(new) # but cleanly decodes as UTF-8
        except UnicodeDecodeError:
            pass # binary, leave unmodified
    else:
        new = encoding.tolocal(new) # normal path

    if util.safehasattr(proto, 'restore'):

        proto.redirect()

        try:
            r = repo.pushkey(encoding.tolocal(namespace), encoding.tolocal(key),
                             encoding.tolocal(old), new) or False
        except util.Abort:
            r = False

        output = proto.restore()

        return '%s\n%s' % (int(r), output)

    r = repo.pushkey(encoding.tolocal(namespace), encoding.tolocal(key),
                     encoding.tolocal(old), new)
    return '%s\n' % int(r)

def _allowstream(ui):
    return ui.configbool('server', 'uncompressed', True, untrusted=True)

@wireprotocommand('stream_out')
def stream(repo, proto):
    '''If the server supports streaming clone, it advertises the "stream"
    capability with a value representing the version and flags of the repo
    it is serving. Client checks to see if it understands the format.
    '''
    if not _allowstream(repo.ui):
        return '1\n'

    def getstream(it):
        yield '0\n'
        for chunk in it:
            yield chunk

    try:
        # LockError may be raised before the first result is yielded. Don't
        # emit output until we're sure we got the lock successfully.
        it = exchange.generatestreamclone(repo)
        return streamres(getstream(it))
    except error.LockError:
        return '2\n'

@wireprotocommand('unbundle', 'heads')
def unbundle(repo, proto, heads):
    their_heads = decodelist(heads)

    try:
        proto.redirect()

        exchange.check_heads(repo, their_heads, 'preparing changes')

        # write bundle data to temporary file because it can be big
        fd, tempname = tempfile.mkstemp(prefix='hg-unbundle-')
        fp = os.fdopen(fd, 'wb+')
        r = 0
        try:
            proto.getfile(fp)
            fp.seek(0)
            gen = exchange.readbundle(repo.ui, fp, None)
            r = exchange.unbundle(repo, gen, their_heads, 'serve',
                                  proto._client())
            if util.safehasattr(r, 'addpart'):
                # The return looks streamable, we are in the bundle2 case and
                # should return a stream.
                return streamres(r.getchunks())
            return pushres(r)

        finally:
            fp.close()
            os.unlink(tempname)

    except (error.BundleValueError, util.Abort, error.PushRaced), exc:
        # handle non-bundle2 case first
        if not getattr(exc, 'duringunbundle2', False):
            try:
                raise
            except util.Abort:
                # The old code we moved used sys.stderr directly.
                # We did not change it to minimise code change.
                # This need to be moved to something proper.
                # Feel free to do it.
                sys.stderr.write("abort: %s\n" % exc)
                return pushres(0)
            except error.PushRaced:
                return pusherr(str(exc))

        bundler = bundle2.bundle20(repo.ui)
        for out in getattr(exc, '_bundle2salvagedoutput', ()):
            bundler.addpart(out)
        try:
            raise
        except error.BundleValueError, exc:
            errpart = bundler.newpart('error:unsupportedcontent')
            if exc.parttype is not None:
                errpart.addparam('parttype', exc.parttype)
            if exc.params:
                errpart.addparam('params', '\0'.join(exc.params))
        except util.Abort, exc:
            manargs = [('message', str(exc))]
            advargs = []
            if exc.hint is not None:
                advargs.append(('hint', exc.hint))
            bundler.addpart(bundle2.bundlepart('error:abort',
                                               manargs, advargs))
        except error.PushRaced, exc:
            bundler.newpart('error:pushraced', [('message', str(exc))])
        return streamres(bundler.getchunks())