amend: add noise in extra to avoid creating obsolescence cycle (
issue3664)
Obsolescence cycle are bad and should be avoided as much as possible. The
current amend implemented touch changeset meta data as few as possible. This
make is easy for amend to result in the same node than a precursors. We add some
deterministic noise in extra to avoid this. In practice, the hex of the amended
changeset is stored in 'amend_source' extra key.
# 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.
from node import nullid
from i18n import _
import random, util, dagutil
def _updatesample(dag, nodes, sample, always, quicksamplesize=0):
# if nodes is empty we scan the entire graph
if nodes:
heads = dag.headsetofconnecteds(nodes)
else:
heads = dag.heads()
dist = {}
visit = util.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:
if curr not in always: # need this check for the early exit below
sample.add(curr)
if quicksamplesize and (len(sample) >= quicksamplesize):
return
seen.add(curr)
for p in dag.parents(curr):
if not nodes or p in nodes:
dist.setdefault(p, d + 1)
visit.append(p)
def _setupsample(dag, nodes, size):
if len(nodes) <= size:
return set(nodes), None, 0
always = dag.headsetofconnecteds(nodes)
desiredlen = size - len(always)
if desiredlen <= 0:
# This could be bad if there are very many heads, all unknown to the
# server. We're counting on long request support here.
return always, None, desiredlen
return always, set(), desiredlen
def _takequicksample(dag, nodes, size, initial):
always, sample, desiredlen = _setupsample(dag, nodes, size)
if sample is None:
return always
if initial:
fromset = None
else:
fromset = nodes
_updatesample(dag, fromset, sample, always, quicksamplesize=desiredlen)
sample.update(always)
return sample
def _takefullsample(dag, nodes, size):
always, sample, desiredlen = _setupsample(dag, nodes, size)
if sample is None:
return always
# update from heads
_updatesample(dag, nodes, sample, always)
# update from roots
_updatesample(dag.inverse(), nodes, sample, always)
assert sample
if len(sample) > desiredlen:
sample = set(random.sample(sample, desiredlen))
elif len(sample) < desiredlen:
more = desiredlen - len(sample)
sample.update(random.sample(list(nodes - sample - always), more))
sample.update(always)
return sample
def findcommonheads(ui, local, remote,
initialsamplesize=100,
fullsamplesize=200,
abortwhenunrelated=True):
'''Return a tuple (common, anyincoming, remoteheads) used to identify
missing nodes from or in remote.
'''
roundtrips = 0
cl = local.changelog
dag = dagutil.revlogdag(cl)
# early exit if we know all the specified remote heads already
ui.debug("query 1; heads\n")
roundtrips += 1
ownheads = dag.heads()
sample = ownheads
if remote.local():
# stopgap until we have a proper localpeer that supports batch()
srvheadhashes = remote.heads()
yesno = remote.known(dag.externalizeall(sample))
elif remote.capable('batch'):
batch = remote.batch()
srvheadhashesref = batch.heads()
yesnoref = batch.known(dag.externalizeall(sample))
batch.submit()
srvheadhashes = srvheadhashesref.value
yesno = yesnoref.value
else:
# compatibility with pre-batch, but post-known remotes during 1.9
# development
srvheadhashes = remote.heads()
sample = []
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 = dag.internalizeall(srvheadhashes, filterunknown=True)
if len(srvheads) == len(srvheadhashes):
ui.debug("all remote heads known locally\n")
return (srvheadhashes, False, srvheadhashes,)
if sample and util.all(yesno):
ui.note(_("all local heads known remotely\n"))
ownheadhashes = dag.externalizeall(ownheads)
return (ownheadhashes, True, srvheadhashes,)
# full blown discovery
# own nodes where I don't know if remote knows them
undecided = dag.nodeset()
# own nodes I know we both know
common = set()
# own nodes I know remote lacks
missing = set()
# treat remote heads (and maybe own heads) as a first implicit sample
# response
common.update(dag.ancestorset(srvheads))
undecided.difference_update(common)
full = False
while undecided:
if sample:
commoninsample = set(n for i, n in enumerate(sample) if yesno[i])
common.update(dag.ancestorset(commoninsample, common))
missinginsample = [n for i, n in enumerate(sample) if not yesno[i]]
missing.update(dag.descendantset(missinginsample, missing))
undecided.difference_update(missing)
undecided.difference_update(common)
if not undecided:
break
if full:
ui.note(_("sampling from both directions\n"))
sample = _takefullsample(dag, undecided, size=fullsamplesize)
elif common:
# use cheapish initial sample
ui.debug("taking initial sample\n")
sample = _takefullsample(dag, undecided, size=fullsamplesize)
else:
# use even cheaper initial sample
ui.debug("taking quick initial sample\n")
sample = _takequicksample(dag, undecided, size=initialsamplesize,
initial=True)
roundtrips += 1
ui.progress(_('searching'), roundtrips, unit=_('queries'))
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)
yesno = remote.known(dag.externalizeall(sample))
full = True
result = dag.headsetofconnecteds(common)
ui.progress(_('searching'), None)
ui.debug("%d total queries\n" % roundtrips)
if not result and srvheadhashes != [nullid]:
if abortwhenunrelated:
raise util.Abort(_("repository is unrelated"))
else:
ui.warn(_("warning: repository is unrelated\n"))
return (set([nullid]), True, srvheadhashes,)
anyincoming = (srvheadhashes != [nullid])
return dag.externalizeall(result), anyincoming, srvheadhashes