annotate mercurial/exchangev2.py @ 39631:b9e453d683a1

exchangev2: fetch changeset revisions

All Mercurial repository data is derived from changesets:
you can't do anything unless you have changesets. Therefore,
it makes sense for changesets to be the first piece of data
that we transfer as part of pull.

To do this, we call our new "changesetdata" command, requesting
parents and revision data. This gives us all the data that a
changegroup delta group would give us. We simply normalize
this data into what addgroup() expects and call that API on
the changelog to bulk insert revisions into the changelog.

Code in this commit is heavily borrowed from
changegroup.cg1unpacker.apply().

Differential Revision: https://phab.mercurial-scm.org/D4482

# exchangev2.py - repository exchange for wire protocol version 2
#
# Copyright 2018 Gregory Szorc <[e-mail]>
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.

from __future__ import absolute_import

import weakref

from .i18n import _
from .node import (
    nullid,
    short,
)
from . import (
    mdiff,
    pycompat,
    setdiscovery,
)

def pull(pullop):
    """Pull using wire protocol version 2."""
    repo = pullop.repo
    remote = pullop.remote
    tr = pullop.trmanager.transaction()

    # Figure out what needs to be fetched.
    common, fetch, remoteheads = _pullchangesetdiscovery(
        repo, remote, pullop.heads, abortwhenunrelated=pullop.force)

    pullheads = pullop.heads or remoteheads
    _fetchchangesets(repo, tr, remote, common, fetch, pullheads)

def _pullchangesetdiscovery(repo, remote, heads, abortwhenunrelated=True):
    """Determine which changesets need to be pulled."""

    if heads:
        knownnode = repo.changelog.hasnode
        if all(knownnode(head) for head in heads):
            return heads, False, heads

    # TODO wire protocol version 2 is capable of more efficient discovery
    # than setdiscovery. Consider implementing something better.
    common, fetch, remoteheads = setdiscovery.findcommonheads(
        repo.ui, repo, remote, abortwhenunrelated=abortwhenunrelated)

    common = set(common)
    remoteheads = set(remoteheads)

    # If a remote head is filtered locally, put it back in the common set.
    # See the comment in exchange._pulldiscoverychangegroup() for more.

    if fetch and remoteheads:
        nodemap = repo.unfiltered().changelog.nodemap

        common |= {head for head in remoteheads if head in nodemap}

        if set(remoteheads).issubset(common):
            fetch = []

    common.discard(nullid)

    return common, fetch, remoteheads

def _fetchchangesets(repo, tr, remote, common, fetch, remoteheads):
    if not fetch:
        return

    # TODO consider adding a step here where we obtain the DAG shape first
    # (or ask the server to slice changesets into chunks for us) so that
    # we can perform multiple fetches in batches. This will facilitate
    # resuming interrupted clones, higher server-side cache hit rates due
    # to smaller segments, etc.
    with remote.commandexecutor() as e:
        objs = e.callcommand(b'changesetdata', {
            b'noderange': [sorted(common), sorted(remoteheads)],
            b'fields': {b'parents', b'revision'},
        }).result()

        # The context manager waits on all response data when exiting. So
        # we need to remain in the context manager in order to stream data.
        return _processchangesetdata(repo, tr, objs)

def _processchangesetdata(repo, tr, objs):
    repo.hook('prechangegroup', throw=True,
              **pycompat.strkwargs(tr.hookargs))

    urepo = repo.unfiltered()
    cl = urepo.changelog

    cl.delayupdate(tr)

    # The first emitted object is a header describing the data that
    # follows.
    meta = next(objs)

    progress = repo.ui.makeprogress(_('changesets'),
                                    unit=_('chunks'),
                                    total=meta.get(b'totalitems'))

    def linkrev(node):
        repo.ui.debug('add changeset %s\n' % short(node))
        # Linkrev for changelog is always self.
        return len(cl)

    def onchangeset(cl, node):
        progress.increment()

    # addgroup() expects a 7-tuple describing revisions. This normalizes
    # the wire data to that format.
    def iterrevisions():
        for cset in objs:
            assert b'revisionsize' in cset
            data = next(objs)

            yield (
                cset[b'node'],
                cset[b'parents'][0],
                cset[b'parents'][1],
                # Linknode is always itself for changesets.
                cset[b'node'],
                # We always send full revisions. So delta base is not set.
                nullid,
                mdiff.trivialdiffheader(len(data)) + data,
                # Flags not yet supported.
                0,
            )

    added = cl.addgroup(iterrevisions(), linkrev, weakref.proxy(tr),
                        addrevisioncb=onchangeset)

    progress.complete()

    return {
        'added': added,
    }