mercurial/server.py

transaction: avoid file stat ambiguity only for files in blacklist

Advancing mtime by os.utime() fails for EPERM, if the target file is
owned by another. bff5ccbe5ead and related changes made some code
paths give advancing mtime up in such case, to fix issue5418.

This causes file stat ambiguity (again), if it is owned by another.

    https://www.mercurial-scm.org/wiki/ExactCacheValidationPlan

To avoid file stat ambiguity in such case, especially for
.hg/dirstate, ed66ec39933f made vfs.rename() copy the target file, and
advance mtime of renamed one again, if EPERM (see issue5584 for detail).

But straightforward "copy if EPERM" isn't reasonable for truncation of
append-only files at rollbacking, because rollbacking might cost much
for truncation of many filelogs, even though filelogs aren't
filecache-ed.

Therefore, this patch introduces blacklist "checkambigfiles", and
avoids file stat ambiguity only for files specified in this blacklist.

This patch consists of two parts below, which should be applied at
once in order to avoid regression.

  - specify 'checkambig=True' at vfs.open(mode='a') in _playback()
    according to checkambigfiles

  - invoke _playback() with checkambigfiles
    - add transaction.__init__() checkambigfiles argument, for _abort()
      - make localrepo instantiate transaction with _cachedfiles
    - add rollback() checkambigfiles argument, for "hg rollback/recover"
      - make localrepo invoke rollback() with _cachedfiles

After this patch, straightforward "copy if EPERM" will be reasonable
at closing the file opened with checkambig=True, because this policy
is applied only on files, which are listed in blacklist
"checkambigfiles".

# server.py - utility and factory of server
#
# Copyright 2005-2007 Matt Mackall <[e-mail]>
#
# 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 tempfile

from .i18n import _

from . import (
    chgserver,
    cmdutil,
    commandserver,
    error,
    hgweb,
    pycompat,
    util,
)

def runservice(opts, parentfn=None, initfn=None, runfn=None, logfile=None,
               runargs=None, appendpid=False):
    '''Run a command as a service.'''

    def writepid(pid):
        if opts['pid_file']:
            if appendpid:
                mode = 'ab'
            else:
                mode = 'wb'
            fp = open(opts['pid_file'], mode)
            fp.write('%d\n' % pid)
            fp.close()

    if opts['daemon'] and not opts['daemon_postexec']:
        # Signal child process startup with file removal
        lockfd, lockpath = tempfile.mkstemp(prefix='hg-service-')
        os.close(lockfd)
        try:
            if not runargs:
                runargs = util.hgcmd() + pycompat.sysargv[1:]
            runargs.append('--daemon-postexec=unlink:%s' % lockpath)
            # Don't pass --cwd to the child process, because we've already
            # changed directory.
            for i in xrange(1, len(runargs)):
                if runargs[i].startswith('--cwd='):
                    del runargs[i]
                    break
                elif runargs[i].startswith('--cwd'):
                    del runargs[i:i + 2]
                    break
            def condfn():
                return not os.path.exists(lockpath)
            pid = util.rundetached(runargs, condfn)
            if pid < 0:
                raise error.Abort(_('child process failed to start'))
            writepid(pid)
        finally:
            util.tryunlink(lockpath)
        if parentfn:
            return parentfn(pid)
        else:
            return

    if initfn:
        initfn()

    if not opts['daemon']:
        writepid(util.getpid())

    if opts['daemon_postexec']:
        try:
            os.setsid()
        except AttributeError:
            pass
        for inst in opts['daemon_postexec']:
            if inst.startswith('unlink:'):
                lockpath = inst[7:]
                os.unlink(lockpath)
            elif inst.startswith('chdir:'):
                os.chdir(inst[6:])
            elif inst != 'none':
                raise error.Abort(_('invalid value for --daemon-postexec: %s')
                                  % inst)
        util.hidewindow()
        util.stdout.flush()
        util.stderr.flush()

        nullfd = os.open(os.devnull, os.O_RDWR)
        logfilefd = nullfd
        if logfile:
            logfilefd = os.open(logfile, os.O_RDWR | os.O_CREAT | os.O_APPEND)
        os.dup2(nullfd, 0)
        os.dup2(logfilefd, 1)
        os.dup2(logfilefd, 2)
        if nullfd not in (0, 1, 2):
            os.close(nullfd)
        if logfile and logfilefd not in (0, 1, 2):
            os.close(logfilefd)

    if runfn:
        return runfn()

_cmdservicemap = {
    'chgunix': chgserver.chgunixservice,
    'pipe': commandserver.pipeservice,
    'unix': commandserver.unixforkingservice,
}

def _createcmdservice(ui, repo, opts):
    mode = opts['cmdserver']
    try:
        return _cmdservicemap[mode](ui, repo, opts)
    except KeyError:
        raise error.Abort(_('unknown mode %s') % mode)

def _createhgwebservice(ui, repo, opts):
    # this way we can check if something was given in the command-line
    if opts.get('port'):
        opts['port'] = util.getport(opts.get('port'))

    alluis = {ui}
    if repo:
        baseui = repo.baseui
        alluis.update([repo.baseui, repo.ui])
    else:
        baseui = ui
    webconf = opts.get('web_conf') or opts.get('webdir_conf')
    if webconf:
        if opts.get('subrepos'):
            raise error.Abort(_('--web-conf cannot be used with --subrepos'))

        # load server settings (e.g. web.port) to "copied" ui, which allows
        # hgwebdir to reload webconf cleanly
        servui = ui.copy()
        servui.readconfig(webconf, sections=['web'])
        alluis.add(servui)
    elif opts.get('subrepos'):
        servui = ui

        # If repo is None, hgweb.createapp() already raises a proper abort
        # message as long as webconf is None.
        if repo:
            webconf = dict()
            cmdutil.addwebdirpath(repo, "", webconf)
    else:
        servui = ui

    optlist = ("name templates style address port prefix ipv6"
               " accesslog errorlog certificate encoding")
    for o in optlist.split():
        val = opts.get(o, '')
        if val in (None, ''): # should check against default options instead
            continue
        for u in alluis:
            u.setconfig("web", o, val, 'serve')

    app = hgweb.createapp(baseui, repo, webconf)
    return hgweb.httpservice(servui, app, opts)

def createservice(ui, repo, opts):
    if opts["cmdserver"]:
        return _createcmdservice(ui, repo, opts)
    else:
        return _createhgwebservice(ui, repo, opts)