hgext/narrow/narrowwirepeer.py

commandserver: add IPC channel to teach repository path on command finished

The idea is to load recently-used repositories first in the master process,
and fork(). The forked worker can reuse a warm repository if it's preloaded.

There are a couple of ways of in-memory repository caching. They have pros
and cons:

 a. "preload by master"
    pros: can use a single cache dict, maximizing cache hit rate
    cons: need to reload a repo in master process (because worker process
          dies per command)
 b. "prefork"
    pros: can cache a repo without reloading (as worker processes persist)
    cons: lower cache hit rate since each worker has to maintain its own cache
 c. "shared memory" (or separate key-value store server)
    pros: no need to reload a repo in master process, ideally
    cons: need to serialize objects to sharable form

Since my primary goal is to get rid of the cost of loading obsstore without
massive rewrites, (c) doesn't work. (b) isn't ideal since it would require
much more SDRAMs than (a). So I take (a).

The idea credits to Jun Wu.

# narrowwirepeer.py - passes narrow spec with unbundle command
#
# Copyright 2017 Google, Inc.
#
# 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

from mercurial import (
    bundle2,
    error,
    extensions,
    hg,
    narrowspec,
    pycompat,
    wireprototypes,
    wireprotov1peer,
    wireprotov1server,
)

def uisetup():
    wireprotov1peer.wirepeer.narrow_widen = peernarrowwiden

def reposetup(repo):
    def wirereposetup(ui, peer):
        def wrapped(orig, cmd, *args, **kwargs):
            if cmd == 'unbundle':
                # TODO: don't blindly add include/exclude wireproto
                # arguments to unbundle.
                include, exclude = repo.narrowpats
                kwargs[r"includepats"] = ','.join(include)
                kwargs[r"excludepats"] = ','.join(exclude)
            return orig(cmd, *args, **kwargs)
        extensions.wrapfunction(peer, '_calltwowaystream', wrapped)
    hg.wirepeersetupfuncs.append(wirereposetup)

@wireprotov1server.wireprotocommand('narrow_widen', 'oldincludes oldexcludes'
                                                    ' newincludes newexcludes'
                                                    ' commonheads cgversion'
                                                    ' known ellipses',
                                    permission='pull')
def narrow_widen(repo, proto, oldincludes, oldexcludes, newincludes,
                 newexcludes, commonheads, cgversion, known, ellipses):
    """wireprotocol command to send data when a narrow clone is widen. We will
    be sending a changegroup here.

    The current set of arguments which are required:
    oldincludes: the old includes of the narrow copy
    oldexcludes: the old excludes of the narrow copy
    newincludes: the new includes of the narrow copy
    newexcludes: the new excludes of the narrow copy
    commonheads: list of heads which are common between the server and client
    cgversion(maybe): the changegroup version to produce
    known: list of nodes which are known on the client (used in ellipses cases)
    ellipses: whether to send ellipses data or not
    """

    preferuncompressed = False
    try:
        oldincludes = wireprototypes.decodelist(oldincludes)
        newincludes = wireprototypes.decodelist(newincludes)
        oldexcludes = wireprototypes.decodelist(oldexcludes)
        newexcludes = wireprototypes.decodelist(newexcludes)
        # validate the patterns
        narrowspec.validatepatterns(set(oldincludes))
        narrowspec.validatepatterns(set(newincludes))
        narrowspec.validatepatterns(set(oldexcludes))
        narrowspec.validatepatterns(set(newexcludes))

        common = wireprototypes.decodelist(commonheads)
        known = None
        if known:
            known = wireprototypes.decodelist(known)
        if ellipses == '0':
            ellipses = False
        else:
            ellipses = bool(ellipses)
        cgversion = cgversion
        newmatch = narrowspec.match(repo.root, include=newincludes,
                                    exclude=newexcludes)
        oldmatch = narrowspec.match(repo.root, include=oldincludes,
                                    exclude=oldexcludes)

        bundler = bundle2.widen_bundle(repo, oldmatch, newmatch, common, known,
                                             cgversion, ellipses)
    except error.Abort as exc:
        bundler = bundle2.bundle20(repo.ui)
        manargs = [('message', pycompat.bytestr(exc))]
        advargs = []
        if exc.hint is not None:
            advargs.append(('hint', exc.hint))
        bundler.addpart(bundle2.bundlepart('error:abort', manargs, advargs))
        preferuncompressed = True

    chunks = bundler.getchunks()
    return wireprototypes.streamres(gen=chunks,
                                    prefer_uncompressed=preferuncompressed)

def peernarrowwiden(remote, **kwargs):
    for ch in (r'oldincludes', r'newincludes', r'oldexcludes', r'newexcludes',
               r'commonheads', r'known'):
        kwargs[ch] = wireprototypes.encodelist(kwargs[ch])

    kwargs[r'ellipses'] = '%i' % bool(kwargs[r'ellipses'])
    f = remote._callcompressable('narrow_widen', **kwargs)
    return bundle2.getunbundler(remote.ui, f)