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hg: obtain lock when creating share from pooled repo (issue5104)...
hg: obtain lock when creating share from pooled repo (issue5104) There are race conditions between clients performing a shared clone to pooled storage: 1) Clients race to create the new shared repo in the pool directory 2) 1 client is seeding the repo in the pool directory and another goes to share it before it is fully cloned We prevent these race conditions by obtaining a lock in the pool directory that is derived from the name of the repo we will be accessing. To test this, a simple generic "lockdelay" extension has been added. The extension inserts an optional, configurable delay before or after lock acquisition. In the test, we delay 2 seconds after lock acquisition in the first process and 1 second before lock acquisition in the 2nd process. This means the first process has 1s to obtain the lock. There is a race condition here. If we encounter it in the wild, we could change the dummy extension to wait on the lock file to appear instead of relying on timing. But that's more complicated. Let's see what happens first.

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r28289:d493d647 3.7.2 stable
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basestore.py
221 lines | 7.9 KiB | text/x-python | PythonLexer
# Copyright 2009-2010 Gregory P. Ward
# Copyright 2009-2010 Intelerad Medical Systems Incorporated
# Copyright 2010-2011 Fog Creek Software
# Copyright 2010-2011 Unity Technologies
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
'''base class for store implementations and store-related utility code'''
import re
from mercurial import util, node, hg, error
from mercurial.i18n import _
import lfutil
class StoreError(Exception):
'''Raised when there is a problem getting files from or putting
files to a central store.'''
def __init__(self, filename, hash, url, detail):
self.filename = filename
self.hash = hash
self.url = url
self.detail = detail
def longmessage(self):
return (_("error getting id %s from url %s for file %s: %s\n") %
(self.hash, util.hidepassword(self.url), self.filename,
self.detail))
def __str__(self):
return "%s: %s" % (util.hidepassword(self.url), self.detail)
class basestore(object):
def __init__(self, ui, repo, url):
self.ui = ui
self.repo = repo
self.url = url
def put(self, source, hash):
'''Put source file into the store so it can be retrieved by hash.'''
raise NotImplementedError('abstract method')
def exists(self, hashes):
'''Check to see if the store contains the given hashes. Given an
iterable of hashes it returns a mapping from hash to bool.'''
raise NotImplementedError('abstract method')
def get(self, files):
'''Get the specified largefiles from the store and write to local
files under repo.root. files is a list of (filename, hash)
tuples. Return (success, missing), lists of files successfully
downloaded and those not found in the store. success is a list
of (filename, hash) tuples; missing is a list of filenames that
we could not get. (The detailed error message will already have
been presented to the user, so missing is just supplied as a
summary.)'''
success = []
missing = []
ui = self.ui
at = 0
available = self.exists(set(hash for (_filename, hash) in files))
for filename, hash in files:
ui.progress(_('getting largefiles'), at, unit='lfile',
total=len(files))
at += 1
ui.note(_('getting %s:%s\n') % (filename, hash))
if not available.get(hash):
ui.warn(_('%s: largefile %s not available from %s\n')
% (filename, hash, util.hidepassword(self.url)))
missing.append(filename)
continue
if self._gethash(filename, hash):
success.append((filename, hash))
else:
missing.append(filename)
ui.progress(_('getting largefiles'), None)
return (success, missing)
def _gethash(self, filename, hash):
"""Get file with the provided hash and store it in the local repo's
store and in the usercache.
filename is for informational messages only.
"""
util.makedirs(lfutil.storepath(self.repo, ''))
storefilename = lfutil.storepath(self.repo, hash)
tmpname = storefilename + '.tmp'
tmpfile = util.atomictempfile(tmpname,
createmode=self.repo.store.createmode)
try:
gothash = self._getfile(tmpfile, filename, hash)
except StoreError as err:
self.ui.warn(err.longmessage())
gothash = ""
tmpfile.close()
if gothash != hash:
if gothash != "":
self.ui.warn(_('%s: data corruption (expected %s, got %s)\n')
% (filename, hash, gothash))
util.unlink(tmpname)
return False
util.rename(tmpname, storefilename)
lfutil.linktousercache(self.repo, hash)
return True
def verify(self, revs, contents=False):
'''Verify the existence (and, optionally, contents) of every big
file revision referenced by every changeset in revs.
Return 0 if all is well, non-zero on any errors.'''
failed = False
self.ui.status(_('searching %d changesets for largefiles\n') %
len(revs))
verified = set() # set of (filename, filenode) tuples
for rev in revs:
cctx = self.repo[rev]
cset = "%d:%s" % (cctx.rev(), node.short(cctx.node()))
for standin in cctx:
if self._verifyfile(cctx, cset, contents, standin, verified):
failed = True
numrevs = len(verified)
numlfiles = len(set([fname for (fname, fnode) in verified]))
if contents:
self.ui.status(
_('verified contents of %d revisions of %d largefiles\n')
% (numrevs, numlfiles))
else:
self.ui.status(
_('verified existence of %d revisions of %d largefiles\n')
% (numrevs, numlfiles))
return int(failed)
def _getfile(self, tmpfile, filename, hash):
'''Fetch one revision of one file from the store and write it
to tmpfile. Compute the hash of the file on-the-fly as it
downloads and return the hash. Close tmpfile. Raise
StoreError if unable to download the file (e.g. it does not
exist in the store).'''
raise NotImplementedError('abstract method')
def _verifyfile(self, cctx, cset, contents, standin, verified):
'''Perform the actual verification of a file in the store.
'cset' is only used in warnings.
'contents' controls verification of content hash.
'standin' is the standin path of the largefile to verify.
'verified' is maintained as a set of already verified files.
Returns _true_ if it is a standin and any problems are found!
'''
raise NotImplementedError('abstract method')
import localstore, wirestore
_storeprovider = {
'file': [localstore.localstore],
'http': [wirestore.wirestore],
'https': [wirestore.wirestore],
'ssh': [wirestore.wirestore],
}
_scheme_re = re.compile(r'^([a-zA-Z0-9+-.]+)://')
# During clone this function is passed the src's ui object
# but it needs the dest's ui object so it can read out of
# the config file. Use repo.ui instead.
def _openstore(repo, remote=None, put=False):
ui = repo.ui
if not remote:
lfpullsource = getattr(repo, 'lfpullsource', None)
if lfpullsource:
path = ui.expandpath(lfpullsource)
elif put:
path = ui.expandpath('default-push', 'default')
else:
path = ui.expandpath('default')
# ui.expandpath() leaves 'default-push' and 'default' alone if
# they cannot be expanded: fallback to the empty string,
# meaning the current directory.
if path == 'default-push' or path == 'default':
path = ''
remote = repo
else:
path, _branches = hg.parseurl(path)
remote = hg.peer(repo, {}, path)
# The path could be a scheme so use Mercurial's normal functionality
# to resolve the scheme to a repository and use its path
path = util.safehasattr(remote, 'url') and remote.url() or remote.path
match = _scheme_re.match(path)
if not match: # regular filesystem path
scheme = 'file'
else:
scheme = match.group(1)
try:
storeproviders = _storeprovider[scheme]
except KeyError:
raise error.Abort(_('unsupported URL scheme %r') % scheme)
for classobj in storeproviders:
try:
return classobj(ui, repo, remote)
except lfutil.storeprotonotcapable:
pass
raise error.Abort(_('%s does not appear to be a largefile store') %
util.hidepassword(path))