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procutil: avoid using os.fork() to implement runbgcommand...
procutil: avoid using os.fork() to implement runbgcommand We ran into the following deadlock: - some command creates an ssh peer, then raises without explicitly closing the peer (hg id + extension in our case) - dispatch catches the exception, calls ui.log('commandfinish', ..) (the sshpeer is still not closed), which calls logtoprocess, which calls procutil.runbgcommand. - in the child of runbgcommand's fork(), between the fork and the exec, the opening of file descriptors triggers a gc which runs the destructor for sshpeer, which waits on ssh's stderr being closed, which never happens since ssh's stderr is held open by the parent of the fork where said destructor hasn't run Remotefilelog appears to have a hack around this deadlock as well. I don't know if there's more subtlety to it, because even though the problem is determistic, it is very fragile, so I didn't manage to reduce it. I can imagine three ways of tackling this problem: 1. don't run any python between fork and exec in runbgcommand 2. make the finalizer harmless after the fork 3. close the peer without relying on gc behavior This commit goes with 1, as forking without exec'ing is tricky in general in a language with gc finalizers. And maybe it's better in the presence of rust threads. A future commit will try 2 or 3. Performance wise: at low memory usage, it's an improvement. At higher memory usage, it's about 2x faster than before when ensurestart=True, but 2x slower when ensurestart=False. Not sure if that matters. The reason for that last bit is that the subprocess.Popen always waits for the execve to finish, and at high memory usage, execve is slow because it deallocates the large page table. Numbers and script: before after mem=1.0GB, ensurestart=True 52.1ms 26.0ms mem=1.0GB, ensurestart=False 14.7ms 26.0ms mem=0.5GB, ensurestart=True 23.2ms 11.2ms mem=0.5GB, ensurestart=False 6.2ms 11.3ms mem=0.2GB, ensurestart=True 15.7ms 7.4ms mem=0.2GB, ensurestart=False 4.3ms 8.1ms mem=0.0GB, ensurestart=True 2.3ms 0.7ms mem=0.0GB, ensurestart=False 0.8ms 0.8ms import time for memsize in [1_000_000_000, 500_000_000, 250_000_000, 0]: mem = 'a' * memsize for ensurestart in [True, False]: now = time.time() n = 100 for i in range(n): procutil.runbgcommand([b'true'], {}, ensurestart=ensurestart) after = time.time() ms = (after - now) / float(n) * 1000 print(f'mem={memsize / 1e9:.1f}GB, ensurestart={ensurestart} -> {ms:.1f}ms') Differential Revision: https://phab.mercurial-scm.org/D9019

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repair.py
546 lines | 17.7 KiB | text/x-python | PythonLexer
# repair.py - functions for repository repair for mercurial
#
# Copyright 2005, 2006 Chris Mason <mason@suse.com>
# Copyright 2007 Olivia Mackall
#
# 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 errno
from .i18n import _
from .node import (
hex,
short,
)
from . import (
bundle2,
changegroup,
discovery,
error,
exchange,
obsolete,
obsutil,
pathutil,
phases,
pycompat,
requirements,
scmutil,
util,
)
from .utils import (
hashutil,
stringutil,
)
def backupbundle(
repo, bases, heads, node, suffix, compress=True, obsolescence=True
):
"""create a bundle with the specified revisions as a backup"""
backupdir = b"strip-backup"
vfs = repo.vfs
if not vfs.isdir(backupdir):
vfs.mkdir(backupdir)
# Include a hash of all the nodes in the filename for uniqueness
allcommits = repo.set(b'%ln::%ln', bases, heads)
allhashes = sorted(c.hex() for c in allcommits)
totalhash = hashutil.sha1(b''.join(allhashes)).digest()
name = b"%s/%s-%s-%s.hg" % (
backupdir,
short(node),
hex(totalhash[:4]),
suffix,
)
cgversion = changegroup.localversion(repo)
comp = None
if cgversion != b'01':
bundletype = b"HG20"
if compress:
comp = b'BZ'
elif compress:
bundletype = b"HG10BZ"
else:
bundletype = b"HG10UN"
outgoing = discovery.outgoing(repo, missingroots=bases, ancestorsof=heads)
contentopts = {
b'cg.version': cgversion,
b'obsolescence': obsolescence,
b'phases': True,
}
return bundle2.writenewbundle(
repo.ui,
repo,
b'strip',
name,
bundletype,
outgoing,
contentopts,
vfs,
compression=comp,
)
def _collectfiles(repo, striprev):
"""find out the filelogs affected by the strip"""
files = set()
for x in pycompat.xrange(striprev, len(repo)):
files.update(repo[x].files())
return sorted(files)
def _collectrevlog(revlog, striprev):
_, brokenset = revlog.getstrippoint(striprev)
return [revlog.linkrev(r) for r in brokenset]
def _collectbrokencsets(repo, files, striprev):
"""return the changesets which will be broken by the truncation"""
s = set()
for revlog in manifestrevlogs(repo):
s.update(_collectrevlog(revlog, striprev))
for fname in files:
s.update(_collectrevlog(repo.file(fname), striprev))
return s
def strip(ui, repo, nodelist, backup=True, topic=b'backup'):
# This function requires the caller to lock the repo, but it operates
# within a transaction of its own, and thus requires there to be no current
# transaction when it is called.
if repo.currenttransaction() is not None:
raise error.ProgrammingError(b'cannot strip from inside a transaction')
# Simple way to maintain backwards compatibility for this
# argument.
if backup in [b'none', b'strip']:
backup = False
repo = repo.unfiltered()
repo.destroying()
vfs = repo.vfs
# load bookmark before changelog to avoid side effect from outdated
# changelog (see repo._refreshchangelog)
repo._bookmarks
cl = repo.changelog
# TODO handle undo of merge sets
if isinstance(nodelist, bytes):
nodelist = [nodelist]
striplist = [cl.rev(node) for node in nodelist]
striprev = min(striplist)
files = _collectfiles(repo, striprev)
saverevs = _collectbrokencsets(repo, files, striprev)
# Some revisions with rev > striprev may not be descendants of striprev.
# We have to find these revisions and put them in a bundle, so that
# we can restore them after the truncations.
# To create the bundle we use repo.changegroupsubset which requires
# the list of heads and bases of the set of interesting revisions.
# (head = revision in the set that has no descendant in the set;
# base = revision in the set that has no ancestor in the set)
tostrip = set(striplist)
saveheads = set(saverevs)
for r in cl.revs(start=striprev + 1):
if any(p in tostrip for p in cl.parentrevs(r)):
tostrip.add(r)
if r not in tostrip:
saverevs.add(r)
saveheads.difference_update(cl.parentrevs(r))
saveheads.add(r)
saveheads = [cl.node(r) for r in saveheads]
# compute base nodes
if saverevs:
descendants = set(cl.descendants(saverevs))
saverevs.difference_update(descendants)
savebases = [cl.node(r) for r in saverevs]
stripbases = [cl.node(r) for r in tostrip]
stripobsidx = obsmarkers = ()
if repo.ui.configbool(b'devel', b'strip-obsmarkers'):
obsmarkers = obsutil.exclusivemarkers(repo, stripbases)
if obsmarkers:
stripobsidx = [
i for i, m in enumerate(repo.obsstore) if m in obsmarkers
]
newbmtarget, updatebm = _bookmarkmovements(repo, tostrip)
backupfile = None
node = nodelist[-1]
if backup:
backupfile = _createstripbackup(repo, stripbases, node, topic)
# create a changegroup for all the branches we need to keep
tmpbundlefile = None
if saveheads:
# do not compress temporary bundle if we remove it from disk later
#
# We do not include obsolescence, it might re-introduce prune markers
# we are trying to strip. This is harmless since the stripped markers
# are already backed up and we did not touched the markers for the
# saved changesets.
tmpbundlefile = backupbundle(
repo,
savebases,
saveheads,
node,
b'temp',
compress=False,
obsolescence=False,
)
with ui.uninterruptible():
try:
with repo.transaction(b"strip") as tr:
# TODO this code violates the interface abstraction of the
# transaction and makes assumptions that file storage is
# using append-only files. We'll need some kind of storage
# API to handle stripping for us.
oldfiles = set(tr._offsetmap.keys())
oldfiles.update(tr._newfiles)
tr.startgroup()
cl.strip(striprev, tr)
stripmanifest(repo, striprev, tr, files)
for fn in files:
repo.file(fn).strip(striprev, tr)
tr.endgroup()
entries = tr.readjournal()
for file, troffset in entries:
if file in oldfiles:
continue
with repo.svfs(file, b'a', checkambig=True) as fp:
fp.truncate(troffset)
if troffset == 0:
repo.store.markremoved(file)
deleteobsmarkers(repo.obsstore, stripobsidx)
del repo.obsstore
repo.invalidatevolatilesets()
repo._phasecache.filterunknown(repo)
if tmpbundlefile:
ui.note(_(b"adding branch\n"))
f = vfs.open(tmpbundlefile, b"rb")
gen = exchange.readbundle(ui, f, tmpbundlefile, vfs)
if not repo.ui.verbose:
# silence internal shuffling chatter
repo.ui.pushbuffer()
tmpbundleurl = b'bundle:' + vfs.join(tmpbundlefile)
txnname = b'strip'
if not isinstance(gen, bundle2.unbundle20):
txnname = b"strip\n%s" % util.hidepassword(tmpbundleurl)
with repo.transaction(txnname) as tr:
bundle2.applybundle(
repo, gen, tr, source=b'strip', url=tmpbundleurl
)
if not repo.ui.verbose:
repo.ui.popbuffer()
f.close()
with repo.transaction(b'repair') as tr:
bmchanges = [(m, repo[newbmtarget].node()) for m in updatebm]
repo._bookmarks.applychanges(repo, tr, bmchanges)
# remove undo files
for undovfs, undofile in repo.undofiles():
try:
undovfs.unlink(undofile)
except OSError as e:
if e.errno != errno.ENOENT:
ui.warn(
_(b'error removing %s: %s\n')
% (
undovfs.join(undofile),
stringutil.forcebytestr(e),
)
)
except: # re-raises
if backupfile:
ui.warn(
_(b"strip failed, backup bundle stored in '%s'\n")
% vfs.join(backupfile)
)
if tmpbundlefile:
ui.warn(
_(b"strip failed, unrecovered changes stored in '%s'\n")
% vfs.join(tmpbundlefile)
)
ui.warn(
_(
b"(fix the problem, then recover the changesets with "
b"\"hg unbundle '%s'\")\n"
)
% vfs.join(tmpbundlefile)
)
raise
else:
if tmpbundlefile:
# Remove temporary bundle only if there were no exceptions
vfs.unlink(tmpbundlefile)
repo.destroyed()
# return the backup file path (or None if 'backup' was False) so
# extensions can use it
return backupfile
def softstrip(ui, repo, nodelist, backup=True, topic=b'backup'):
"""perform a "soft" strip using the archived phase"""
tostrip = [c.node() for c in repo.set(b'sort(%ln::)', nodelist)]
if not tostrip:
return None
backupfile = None
if backup:
node = tostrip[0]
backupfile = _createstripbackup(repo, tostrip, node, topic)
newbmtarget, updatebm = _bookmarkmovements(repo, tostrip)
with repo.transaction(b'strip') as tr:
phases.retractboundary(repo, tr, phases.archived, tostrip)
bmchanges = [(m, repo[newbmtarget].node()) for m in updatebm]
repo._bookmarks.applychanges(repo, tr, bmchanges)
return backupfile
def _bookmarkmovements(repo, tostrip):
# compute necessary bookmark movement
bm = repo._bookmarks
updatebm = []
for m in bm:
rev = repo[bm[m]].rev()
if rev in tostrip:
updatebm.append(m)
newbmtarget = None
# If we need to move bookmarks, compute bookmark
# targets. Otherwise we can skip doing this logic.
if updatebm:
# For a set s, max(parents(s) - s) is the same as max(heads(::s - s)),
# but is much faster
newbmtarget = repo.revs(b'max(parents(%ld) - (%ld))', tostrip, tostrip)
if newbmtarget:
newbmtarget = repo[newbmtarget.first()].node()
else:
newbmtarget = b'.'
return newbmtarget, updatebm
def _createstripbackup(repo, stripbases, node, topic):
# backup the changeset we are about to strip
vfs = repo.vfs
cl = repo.changelog
backupfile = backupbundle(repo, stripbases, cl.heads(), node, topic)
repo.ui.status(_(b"saved backup bundle to %s\n") % vfs.join(backupfile))
repo.ui.log(
b"backupbundle", b"saved backup bundle to %s\n", vfs.join(backupfile)
)
return backupfile
def safestriproots(ui, repo, nodes):
"""return list of roots of nodes where descendants are covered by nodes"""
torev = repo.unfiltered().changelog.rev
revs = {torev(n) for n in nodes}
# tostrip = wanted - unsafe = wanted - ancestors(orphaned)
# orphaned = affected - wanted
# affected = descendants(roots(wanted))
# wanted = revs
revset = b'%ld - ( ::( (roots(%ld):: and not _phase(%s)) -%ld) )'
tostrip = set(repo.revs(revset, revs, revs, phases.internal, revs))
notstrip = revs - tostrip
if notstrip:
nodestr = b', '.join(sorted(short(repo[n].node()) for n in notstrip))
ui.warn(
_(b'warning: orphaned descendants detected, not stripping %s\n')
% nodestr
)
return [c.node() for c in repo.set(b'roots(%ld)', tostrip)]
class stripcallback(object):
"""used as a transaction postclose callback"""
def __init__(self, ui, repo, backup, topic):
self.ui = ui
self.repo = repo
self.backup = backup
self.topic = topic or b'backup'
self.nodelist = []
def addnodes(self, nodes):
self.nodelist.extend(nodes)
def __call__(self, tr):
roots = safestriproots(self.ui, self.repo, self.nodelist)
if roots:
strip(self.ui, self.repo, roots, self.backup, self.topic)
def delayedstrip(ui, repo, nodelist, topic=None, backup=True):
"""like strip, but works inside transaction and won't strip irreverent revs
nodelist must explicitly contain all descendants. Otherwise a warning will
be printed that some nodes are not stripped.
Will do a backup if `backup` is True. The last non-None "topic" will be
used as the backup topic name. The default backup topic name is "backup".
"""
tr = repo.currenttransaction()
if not tr:
nodes = safestriproots(ui, repo, nodelist)
return strip(ui, repo, nodes, backup=backup, topic=topic)
# transaction postclose callbacks are called in alphabet order.
# use '\xff' as prefix so we are likely to be called last.
callback = tr.getpostclose(b'\xffstrip')
if callback is None:
callback = stripcallback(ui, repo, backup=backup, topic=topic)
tr.addpostclose(b'\xffstrip', callback)
if topic:
callback.topic = topic
callback.addnodes(nodelist)
def stripmanifest(repo, striprev, tr, files):
for revlog in manifestrevlogs(repo):
revlog.strip(striprev, tr)
def manifestrevlogs(repo):
yield repo.manifestlog.getstorage(b'')
if scmutil.istreemanifest(repo):
# This logic is safe if treemanifest isn't enabled, but also
# pointless, so we skip it if treemanifest isn't enabled.
for unencoded, encoded, size in repo.store.datafiles():
if unencoded.startswith(b'meta/') and unencoded.endswith(
b'00manifest.i'
):
dir = unencoded[5:-12]
yield repo.manifestlog.getstorage(dir)
def rebuildfncache(ui, repo):
"""Rebuilds the fncache file from repo history.
Missing entries will be added. Extra entries will be removed.
"""
repo = repo.unfiltered()
if requirements.FNCACHE_REQUIREMENT not in repo.requirements:
ui.warn(
_(
b'(not rebuilding fncache because repository does not '
b'support fncache)\n'
)
)
return
with repo.lock():
fnc = repo.store.fncache
fnc.ensureloaded(warn=ui.warn)
oldentries = set(fnc.entries)
newentries = set()
seenfiles = set()
progress = ui.makeprogress(
_(b'rebuilding'), unit=_(b'changesets'), total=len(repo)
)
for rev in repo:
progress.update(rev)
ctx = repo[rev]
for f in ctx.files():
# This is to minimize I/O.
if f in seenfiles:
continue
seenfiles.add(f)
i = b'data/%s.i' % f
d = b'data/%s.d' % f
if repo.store._exists(i):
newentries.add(i)
if repo.store._exists(d):
newentries.add(d)
progress.complete()
if requirements.TREEMANIFEST_REQUIREMENT in repo.requirements:
# This logic is safe if treemanifest isn't enabled, but also
# pointless, so we skip it if treemanifest isn't enabled.
for dir in pathutil.dirs(seenfiles):
i = b'meta/%s/00manifest.i' % dir
d = b'meta/%s/00manifest.d' % dir
if repo.store._exists(i):
newentries.add(i)
if repo.store._exists(d):
newentries.add(d)
addcount = len(newentries - oldentries)
removecount = len(oldentries - newentries)
for p in sorted(oldentries - newentries):
ui.write(_(b'removing %s\n') % p)
for p in sorted(newentries - oldentries):
ui.write(_(b'adding %s\n') % p)
if addcount or removecount:
ui.write(
_(b'%d items added, %d removed from fncache\n')
% (addcount, removecount)
)
fnc.entries = newentries
fnc._dirty = True
with repo.transaction(b'fncache') as tr:
fnc.write(tr)
else:
ui.write(_(b'fncache already up to date\n'))
def deleteobsmarkers(obsstore, indices):
"""Delete some obsmarkers from obsstore and return how many were deleted
'indices' is a list of ints which are the indices
of the markers to be deleted.
Every invocation of this function completely rewrites the obsstore file,
skipping the markers we want to be removed. The new temporary file is
created, remaining markers are written there and on .close() this file
gets atomically renamed to obsstore, thus guaranteeing consistency."""
if not indices:
# we don't want to rewrite the obsstore with the same content
return
left = []
current = obsstore._all
n = 0
for i, m in enumerate(current):
if i in indices:
n += 1
continue
left.append(m)
newobsstorefile = obsstore.svfs(b'obsstore', b'w', atomictemp=True)
for bytes in obsolete.encodemarkers(left, True, obsstore._version):
newobsstorefile.write(bytes)
newobsstorefile.close()
return n