annotate hgfastobs.py @ 791:5f3b53d74b7f

fastobs: first commit of an extension to test obsolete marker exchange methods

This currently implements the "fill in the box" approach discussed at
the 2.6 sprint, which seems to handle common cases correctly with
significantly less data transferred.

"""Extension to try and speed up transfer of obsolete markers.

Mercurial 2.6 transfers obsolete markers in the dumbest way possible:
it simply transfers all of them to the server on every
operation. While this /works/, it's not ideal because it's a large
amount of extra data for users to pull down (1.9M for the 17k obsolete
markers in hg-crew as of this writing in late July 2013). It's also
frustrating because this transfer takes a nontrivial amount of time.

You can specify a strategy with the config knob
obsolete.syncstrategy. Current strategies are "stock" and
"boxfill". Default strategy is presently boxfill.

TODO(durin42): consider better names for sync strategies.
"""
import sys

from mercurial import commands
from mercurial import extensions
from mercurial import obsolete
from mercurial import node
from mercurial.i18n import _

_strategies = {
    'stock': obsolete.syncpush,
    }

def _strategy(name, default=False):
    def inner(func):
        _strategies[name] = func
        if default:
            _strategies[None] = func
        return func
    return inner

def syncpushwrapper(orig, repo, remote):
    stratfn = _strategies[repo.ui.config('obsolete', 'syncstrategy')]
    return stratfn(repo, remote)

extensions.wrapfunction(obsolete, 'syncpush', syncpushwrapper)

def pushmarkerwrapper(orig, repo, *args):
    if repo.ui.config('obsolete', 'syncstrategy') == 'stock':
        return orig(repo, *args)
    # We shouldn't need to do this, since we transmit markers
    # effectively during push in localrepo. Just return success.
    return 1

def _getoutgoing():
    f = sys._getframe(4)
    return f.f_locals['outgoing']

@_strategy('boxfill', default=True)
def boxfill(repo, remote):
    """The "fill in the box" strategy from the 2.6 sprint.

    See the notes[0] from the 2.6 sprint for what "fill in the box"
    means here. It's a fairly subtle algorithm, which may have
    surprising behavior at times, but was the least-bad option
    proposed at the sprint.

    [0]: https://bitbucket.org/durin42/2.6sprint-notes/src/tip/mercurial26-obsstore-rev.1398.txt
    """
    outgoing = _getoutgoing()
    urepo = repo.unfiltered()
    # need to collect obsolete markers which list any of
    # outgoing.missing as a successor (transitively), as well as any
    # kill markers for dead nodes descended from any of the precursors
    # of outgoing.missing.
    boxedges = urepo.revs(
        '(descendants(precursors(%ln)) or descendants(%ln)) and hidden()',
        outgoing.missing, outgoing.missing)
    transmit = []
    for node in boxedges:
        transmit.extend(obsolete.successormarkers(urepo[node]))
    xmit, total = len(transmit), len(repo.obsstore._all)
    repo.ui.status('about to transmit %d obsolete markers (%d markers total)\n'
                   % (xmit, total))
    parts, size, chunk = [], 0, 0
    for marker in transmit:
        enc = obsolete._encodeonemarker(_markertuple(marker))
        parts.append(enc)
        size += len(enc)
        if size > obsolete._maxpayload:
            repo.ui.note(
                'obsolete boxpush: sending a chunk of obsolete markers\n')
            data = ''.join([obsolete._pack('>B', _fmversion)], parts)
            remote.pushkey('obsolete', 'dump%d' % chunk, base85.b85encode(data))
            parts, size = [], 0
            chunk += 1

def _markertuple(marker):
    return marker._data