scmutil: add file object wrapper class to check ambiguity at closing
In Mercurial source tree, opening a file in "a"/"a+" mode like below
doesn't specify atomictemp=True for vfs, and this avoids file stat
ambiguity check by atomictempfile.
- writing changes out in revlog layer uses "a+" mode
- truncation in repair.strip() uses "a" mode
- truncation in transaction._playback() uses "a" mode
If steps below occurs at "the same time in sec", all of mtime, ctime
and size are same between (1) and (3).
1. append data to revlog-style file (and close transaction)
2. discard appended data by truncation (strip or rollback)
3. append same size but different data to revlog-style file again
Therefore, cache validation doesn't work after (3) as expected.
This patch adds file object wrapper class checkambigatclosing to check
(and get rid of) ambiguity at closing. It is used by vfs in subsequent
patch.
This is a part of ExactCacheValidationPlan.
https://www.mercurial-scm.org/wiki/ExactCacheValidationPlan
BTW, checkambigatclosing is tested in test-filecache.py, even though
it doesn't use filecache itself, because filecache assumes that file
stat ambiguity never occurs (and there is no another test-*.py related
to filecache).
# Copyright 2011 Fog Creek Software
#
# 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 os
import re
from mercurial.i18n import _
from mercurial import (
error,
httppeer,
util,
wireproto,
)
from . import (
lfutil,
)
urlerr = util.urlerr
urlreq = util.urlreq
LARGEFILES_REQUIRED_MSG = ('\nThis repository uses the largefiles extension.'
'\n\nPlease enable it in your Mercurial config '
'file.\n')
# these will all be replaced by largefiles.uisetup
capabilitiesorig = None
ssholdcallstream = None
httpoldcallstream = None
def putlfile(repo, proto, sha):
'''Server command for putting a largefile into a repository's local store
and into the user cache.'''
proto.redirect()
path = lfutil.storepath(repo, sha)
util.makedirs(os.path.dirname(path))
tmpfp = util.atomictempfile(path, createmode=repo.store.createmode)
try:
proto.getfile(tmpfp)
tmpfp._fp.seek(0)
if sha != lfutil.hexsha1(tmpfp._fp):
raise IOError(0, _('largefile contents do not match hash'))
tmpfp.close()
lfutil.linktousercache(repo, sha)
except IOError as e:
repo.ui.warn(_('largefiles: failed to put %s into store: %s\n') %
(sha, e.strerror))
return wireproto.pushres(1)
finally:
tmpfp.discard()
return wireproto.pushres(0)
def getlfile(repo, proto, sha):
'''Server command for retrieving a largefile from the repository-local
cache or user cache.'''
filename = lfutil.findfile(repo, sha)
if not filename:
raise error.Abort(_('requested largefile %s not present in cache')
% sha)
f = open(filename, 'rb')
length = os.fstat(f.fileno())[6]
# Since we can't set an HTTP content-length header here, and
# Mercurial core provides no way to give the length of a streamres
# (and reading the entire file into RAM would be ill-advised), we
# just send the length on the first line of the response, like the
# ssh proto does for string responses.
def generator():
yield '%d\n' % length
for chunk in util.filechunkiter(f):
yield chunk
return wireproto.streamres(generator())
def statlfile(repo, proto, sha):
'''Server command for checking if a largefile is present - returns '2\n' if
the largefile is missing, '0\n' if it seems to be in good condition.
The value 1 is reserved for mismatched checksum, but that is too expensive
to be verified on every stat and must be caught be running 'hg verify'
server side.'''
filename = lfutil.findfile(repo, sha)
if not filename:
return '2\n'
return '0\n'
def wirereposetup(ui, repo):
class lfileswirerepository(repo.__class__):
def putlfile(self, sha, fd):
# unfortunately, httprepository._callpush tries to convert its
# input file-like into a bundle before sending it, so we can't use
# it ...
if issubclass(self.__class__, httppeer.httppeer):
res = self._call('putlfile', data=fd, sha=sha,
headers={'content-type':'application/mercurial-0.1'})
try:
d, output = res.split('\n', 1)
for l in output.splitlines(True):
self.ui.warn(_('remote: '), l) # assume l ends with \n
return int(d)
except ValueError:
self.ui.warn(_('unexpected putlfile response: %r\n') % res)
return 1
# ... but we can't use sshrepository._call because the data=
# argument won't get sent, and _callpush does exactly what we want
# in this case: send the data straight through
else:
try:
ret, output = self._callpush("putlfile", fd, sha=sha)
if ret == "":
raise error.ResponseError(_('putlfile failed:'),
output)
return int(ret)
except IOError:
return 1
except ValueError:
raise error.ResponseError(
_('putlfile failed (unexpected response):'), ret)
def getlfile(self, sha):
"""returns an iterable with the chunks of the file with sha sha"""
stream = self._callstream("getlfile", sha=sha)
length = stream.readline()
try:
length = int(length)
except ValueError:
self._abort(error.ResponseError(_("unexpected response:"),
length))
# SSH streams will block if reading more than length
for chunk in util.filechunkiter(stream, 128 * 1024, length):
yield chunk
# HTTP streams must hit the end to process the last empty
# chunk of Chunked-Encoding so the connection can be reused.
if issubclass(self.__class__, httppeer.httppeer):
chunk = stream.read(1)
if chunk:
self._abort(error.ResponseError(_("unexpected response:"),
chunk))
@wireproto.batchable
def statlfile(self, sha):
f = wireproto.future()
result = {'sha': sha}
yield result, f
try:
yield int(f.value)
except (ValueError, urlerr.httperror):
# If the server returns anything but an integer followed by a
# newline, newline, it's not speaking our language; if we get
# an HTTP error, we can't be sure the largefile is present;
# either way, consider it missing.
yield 2
repo.__class__ = lfileswirerepository
# advertise the largefiles=serve capability
def capabilities(repo, proto):
'''Wrap server command to announce largefile server capability'''
return capabilitiesorig(repo, proto) + ' largefiles=serve'
def heads(repo, proto):
'''Wrap server command - largefile capable clients will know to call
lheads instead'''
if lfutil.islfilesrepo(repo):
return wireproto.ooberror(LARGEFILES_REQUIRED_MSG)
return wireproto.heads(repo, proto)
def sshrepocallstream(self, cmd, **args):
if cmd == 'heads' and self.capable('largefiles'):
cmd = 'lheads'
if cmd == 'batch' and self.capable('largefiles'):
args['cmds'] = args['cmds'].replace('heads ', 'lheads ')
return ssholdcallstream(self, cmd, **args)
headsre = re.compile(r'(^|;)heads\b')
def httprepocallstream(self, cmd, **args):
if cmd == 'heads' and self.capable('largefiles'):
cmd = 'lheads'
if cmd == 'batch' and self.capable('largefiles'):
args['cmds'] = headsre.sub('lheads', args['cmds'])
return httpoldcallstream(self, cmd, **args)