Mercurial > hg
view mercurial/setdiscovery.py @ 39814:d059cb669632
wireprotov2: allow multiple fields to follow revision maps
The *data wire protocol commands emit a series of CBOR values.
Because revision/delta data may be large, their data is emitted
outside the map as a top-level bytestring value.
Before this commit, we'd emit a single optional bytestring
value after the revision descriptor map. This got the job done.
But it was limiting in that we could only send a single field.
And, it required the consumer to know that the presence of a
key in the map implied the existence of a following bytestring
value.
This commit changes the encoding strategy so top-level bytestring
values in the stream are explicitly denoted in a "fieldsfollowing"
key. This key contains an array defining what fields that follow
and the expected size of each field.
By defining things this way, we can easily send N bytestring
values without any ambiguity about their order. In addition,
clients only need to know how to parse ``fieldsfollowing`` to
know if extra values are present.
Because this breaks backwards compatibility, we've bumped the version
number of the wire protocol version 2 API endpoint.
Differential Revision: https://phab.mercurial-scm.org/D4620
author | Gregory Szorc <gregory.szorc@gmail.com> |
---|---|
date | Thu, 20 Sep 2018 12:57:23 -0700 |
parents | 274acf379dbb |
children | 71b0db4fa027 |
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# setdiscovery.py - improved discovery of common nodeset for mercurial # # Copyright 2010 Benoit Boissinot <bboissin@gmail.com> # and Peter Arrenbrecht <peter@arrenbrecht.ch> # # This software may be used and distributed according to the terms of the # GNU General Public License version 2 or any later version. """ Algorithm works in the following way. You have two repository: local and remote. They both contains a DAG of changelists. The goal of the discovery protocol is to find one set of node *common*, the set of nodes shared by local and remote. One of the issue with the original protocol was latency, it could potentially require lots of roundtrips to discover that the local repo was a subset of remote (which is a very common case, you usually have few changes compared to upstream, while upstream probably had lots of development). The new protocol only requires one interface for the remote repo: `known()`, which given a set of changelists tells you if they are present in the DAG. The algorithm then works as follow: - We will be using three sets, `common`, `missing`, `unknown`. Originally all nodes are in `unknown`. - Take a sample from `unknown`, call `remote.known(sample)` - For each node that remote knows, move it and all its ancestors to `common` - For each node that remote doesn't know, move it and all its descendants to `missing` - Iterate until `unknown` is empty There are a couple optimizations, first is instead of starting with a random sample of missing, start by sending all heads, in the case where the local repo is a subset, you computed the answer in one round trip. Then you can do something similar to the bisecting strategy used when finding faulty changesets. Instead of random samples, you can try picking nodes that will maximize the number of nodes that will be classified with it (since all ancestors or descendants will be marked as well). """ from __future__ import absolute_import import collections import random from .i18n import _ from .node import ( nullid, nullrev, ) from . import ( error, util, ) def _updatesample(revs, heads, sample, parentfn, quicksamplesize=0): """update an existing sample to match the expected size The sample is updated with revs exponentially distant from each head of the <revs> set. (H~1, H~2, H~4, H~8, etc). If a target size is specified, the sampling will stop once this size is reached. Otherwise sampling will happen until roots of the <revs> set are reached. :revs: set of revs we want to discover (if None, assume the whole dag) :heads: set of DAG head revs :sample: a sample to update :parentfn: a callable to resolve parents for a revision :quicksamplesize: optional target size of the sample""" dist = {} visit = collections.deque(heads) seen = set() factor = 1 while visit: curr = visit.popleft() if curr in seen: continue d = dist.setdefault(curr, 1) if d > factor: factor *= 2 if d == factor: sample.add(curr) if quicksamplesize and (len(sample) >= quicksamplesize): return seen.add(curr) for p in parentfn(curr): if p != nullrev and (not revs or p in revs): dist.setdefault(p, d + 1) visit.append(p) def _takequicksample(repo, headrevs, revs, size): """takes a quick sample of size <size> It is meant for initial sampling and focuses on querying heads and close ancestors of heads. :dag: a dag object :headrevs: set of head revisions in local DAG to consider :revs: set of revs to discover :size: the maximum size of the sample""" sample = set(repo.revs('heads(%ld)', revs)) if len(sample) >= size: return _limitsample(sample, size) _updatesample(None, headrevs, sample, repo.changelog.parentrevs, quicksamplesize=size) return sample def _takefullsample(repo, headrevs, revs, size): sample = set(repo.revs('heads(%ld)', revs)) # update from heads revsheads = set(repo.revs('heads(%ld)', revs)) _updatesample(revs, revsheads, sample, repo.changelog.parentrevs) # update from roots revsroots = set(repo.revs('roots(%ld)', revs)) # _updatesample() essentially does interaction over revisions to look up # their children. This lookup is expensive and doing it in a loop is # quadratic. We precompute the children for all relevant revisions and # make the lookup in _updatesample() a simple dict lookup. # # Because this function can be called multiple times during discovery, we # may still perform redundant work and there is room to optimize this by # keeping a persistent cache of children across invocations. children = {} parentrevs = repo.changelog.parentrevs for rev in repo.changelog.revs(start=min(revsroots)): # Always ensure revision has an entry so we don't need to worry about # missing keys. children.setdefault(rev, []) for prev in parentrevs(rev): if prev == nullrev: continue children.setdefault(prev, []).append(rev) _updatesample(revs, revsroots, sample, children.__getitem__) assert sample sample = _limitsample(sample, size) if len(sample) < size: more = size - len(sample) sample.update(random.sample(list(revs - sample), more)) return sample def _limitsample(sample, desiredlen): """return a random subset of sample of at most desiredlen item""" if len(sample) > desiredlen: sample = set(random.sample(sample, desiredlen)) return sample def findcommonheads(ui, local, remote, initialsamplesize=100, fullsamplesize=200, abortwhenunrelated=True, ancestorsof=None): '''Return a tuple (common, anyincoming, remoteheads) used to identify missing nodes from or in remote. ''' start = util.timer() roundtrips = 0 cl = local.changelog clnode = cl.node clrev = cl.rev if ancestorsof is not None: ownheads = [clrev(n) for n in ancestorsof] else: ownheads = [rev for rev in cl.headrevs() if rev != nullrev] # early exit if we know all the specified remote heads already ui.debug("query 1; heads\n") roundtrips += 1 sample = _limitsample(ownheads, initialsamplesize) # indices between sample and externalized version must match sample = list(sample) with remote.commandexecutor() as e: fheads = e.callcommand('heads', {}) fknown = e.callcommand('known', { 'nodes': [clnode(r) for r in sample], }) srvheadhashes, yesno = fheads.result(), fknown.result() if cl.tip() == nullid: if srvheadhashes != [nullid]: return [nullid], True, srvheadhashes return [nullid], False, [] # start actual discovery (we note this before the next "if" for # compatibility reasons) ui.status(_("searching for changes\n")) srvheads = [] for node in srvheadhashes: if node == nullid: continue try: srvheads.append(clrev(node)) # Catches unknown and filtered nodes. except error.LookupError: continue if len(srvheads) == len(srvheadhashes): ui.debug("all remote heads known locally\n") return srvheadhashes, False, srvheadhashes if len(sample) == len(ownheads) and all(yesno): ui.note(_("all local heads known remotely\n")) ownheadhashes = [clnode(r) for r in ownheads] return ownheadhashes, True, srvheadhashes # full blown discovery # own nodes I know we both know # treat remote heads (and maybe own heads) as a first implicit sample # response common = cl.incrementalmissingrevs(srvheads) commoninsample = set(n for i, n in enumerate(sample) if yesno[i]) common.addbases(commoninsample) # own nodes where I don't know if remote knows them undecided = set(common.missingancestors(ownheads)) # own nodes I know remote lacks missing = set() full = False progress = ui.makeprogress(_('searching'), unit=_('queries')) while undecided: if sample: missinginsample = [n for i, n in enumerate(sample) if not yesno[i]] if missing: missing.update(local.revs('descendants(%ld) - descendants(%ld)', missinginsample, missing)) else: missing.update(local.revs('descendants(%ld)', missinginsample)) undecided.difference_update(missing) if not undecided: break if full or common.hasbases(): if full: ui.note(_("sampling from both directions\n")) else: ui.debug("taking initial sample\n") samplefunc = _takefullsample targetsize = fullsamplesize else: # use even cheaper initial sample ui.debug("taking quick initial sample\n") samplefunc = _takequicksample targetsize = initialsamplesize if len(undecided) < targetsize: sample = list(undecided) else: sample = samplefunc(local, ownheads, undecided, targetsize) roundtrips += 1 progress.update(roundtrips) ui.debug("query %i; still undecided: %i, sample size is: %i\n" % (roundtrips, len(undecided), len(sample))) # indices between sample and externalized version must match sample = list(sample) with remote.commandexecutor() as e: yesno = e.callcommand('known', { 'nodes': [clnode(r) for r in sample], }).result() full = True if sample: commoninsample = set(n for i, n in enumerate(sample) if yesno[i]) common.addbases(commoninsample) common.removeancestorsfrom(undecided) # heads(common) == heads(common.bases) since common represents common.bases # and all its ancestors # The presence of nullrev will confuse heads(). So filter it out. result = set(local.revs('heads(%ld)', common.bases - {nullrev})) elapsed = util.timer() - start progress.complete() ui.debug("%d total queries in %.4fs\n" % (roundtrips, elapsed)) msg = ('found %d common and %d unknown server heads,' ' %d roundtrips in %.4fs\n') missing = set(result) - set(srvheads) ui.log('discovery', msg, len(result), len(missing), roundtrips, elapsed) if not result and srvheadhashes != [nullid]: if abortwhenunrelated: raise error.Abort(_("repository is unrelated")) else: ui.warn(_("warning: repository is unrelated\n")) return ({nullid}, True, srvheadhashes,) anyincoming = (srvheadhashes != [nullid]) result = {clnode(r) for r in result} return result, anyincoming, srvheadhashes