##// END OF EJS Templates
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

File last commit:

r47575:d4ba4d51 default
r47651:8759e22f default
Show More
server.py
235 lines | 7.0 KiB | text/x-python | PythonLexer
# server.py - utility and factory of server
#
# Copyright 2005-2007 Olivia Mackall <olivia@selenic.com>
#
# 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
from .i18n import _
from .pycompat import open
from . import (
chgserver,
cmdutil,
commandserver,
error,
hgweb,
pycompat,
util,
)
from .utils import procutil
def runservice(
opts,
parentfn=None,
initfn=None,
runfn=None,
logfile=None,
runargs=None,
appendpid=False,
):
'''Run a command as a service.'''
postexecargs = {}
if opts[b'daemon_postexec']:
for inst in opts[b'daemon_postexec']:
if inst.startswith(b'unlink:'):
postexecargs[b'unlink'] = inst[7:]
elif inst.startswith(b'chdir:'):
postexecargs[b'chdir'] = inst[6:]
elif inst != b'none':
raise error.Abort(
_(b'invalid value for --daemon-postexec: %s') % inst
)
# When daemonized on Windows, redirect stdout/stderr to the lockfile (which
# gets cleaned up after the child is up and running), so that the parent can
# read and print the error if this child dies early. See 594dd384803c. On
# other platforms, the child can write to the parent's stdio directly, until
# it is redirected prior to runfn().
if pycompat.iswindows and opts[b'daemon_postexec']:
if b'unlink' in postexecargs and os.path.exists(
postexecargs[b'unlink']
):
procutil.stdout.flush()
procutil.stderr.flush()
fd = os.open(
postexecargs[b'unlink'], os.O_WRONLY | os.O_APPEND | os.O_BINARY
)
try:
os.dup2(fd, procutil.stdout.fileno())
os.dup2(fd, procutil.stderr.fileno())
finally:
os.close(fd)
def writepid(pid):
if opts[b'pid_file']:
if appendpid:
mode = b'ab'
else:
mode = b'wb'
fp = open(opts[b'pid_file'], mode)
fp.write(b'%d\n' % pid)
fp.close()
if opts[b'daemon'] and not opts[b'daemon_postexec']:
# Signal child process startup with file removal
lockfd, lockpath = pycompat.mkstemp(prefix=b'hg-service-')
os.close(lockfd)
try:
if not runargs:
runargs = procutil.hgcmd() + pycompat.sysargv[1:]
runargs.append(b'--daemon-postexec=unlink:%s' % lockpath)
# Don't pass --cwd to the child process, because we've already
# changed directory.
for i in pycompat.xrange(1, len(runargs)):
if runargs[i].startswith(b'--cwd='):
del runargs[i]
break
elif runargs[i].startswith(b'--cwd'):
del runargs[i : i + 2]
break
def condfn():
return not os.path.exists(lockpath)
pid = procutil.rundetached(runargs, condfn)
if pid < 0:
# If the daemonized process managed to write out an error msg,
# report it.
if pycompat.iswindows and os.path.exists(lockpath):
with open(lockpath, b'rb') as log:
for line in log:
procutil.stderr.write(line)
raise error.Abort(_(b'child process failed to start'))
writepid(pid)
finally:
util.tryunlink(lockpath)
if parentfn:
return parentfn(pid)
else:
return
if initfn:
initfn()
if not opts[b'daemon']:
writepid(procutil.getpid())
if opts[b'daemon_postexec']:
try:
os.setsid()
except AttributeError:
pass
if b'chdir' in postexecargs:
os.chdir(postexecargs[b'chdir'])
procutil.hidewindow()
procutil.stdout.flush()
procutil.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, 0o666
)
os.dup2(nullfd, procutil.stdin.fileno())
os.dup2(logfilefd, procutil.stdout.fileno())
os.dup2(logfilefd, procutil.stderr.fileno())
stdio = (
procutil.stdin.fileno(),
procutil.stdout.fileno(),
procutil.stderr.fileno(),
)
if nullfd not in stdio:
os.close(nullfd)
if logfile and logfilefd not in stdio:
os.close(logfilefd)
# Only unlink after redirecting stdout/stderr, so Windows doesn't
# complain about a sharing violation.
if b'unlink' in postexecargs:
os.unlink(postexecargs[b'unlink'])
if runfn:
return runfn()
_cmdservicemap = {
b'chgunix': chgserver.chgunixservice,
b'pipe': commandserver.pipeservice,
b'unix': commandserver.unixforkingservice,
}
def _createcmdservice(ui, repo, opts):
mode = opts[b'cmdserver']
try:
servicefn = _cmdservicemap[mode]
except KeyError:
raise error.Abort(_(b'unknown mode %s') % mode)
commandserver.setuplogging(ui, repo)
return servicefn(ui, repo, opts)
def _createhgwebservice(ui, repo, opts):
# this way we can check if something was given in the command-line
if opts.get(b'port'):
opts[b'port'] = util.getport(opts.get(b'port'))
alluis = {ui}
if repo:
baseui = repo.baseui
alluis.update([repo.baseui, repo.ui])
else:
baseui = ui
webconf = opts.get(b'web_conf') or opts.get(b'webdir_conf')
if webconf:
if opts.get(b'subrepos'):
raise error.Abort(_(b'--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=[b'web'])
alluis.add(servui)
elif opts.get(b'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, b"", webconf)
else:
servui = ui
optlist = (
b"name templates style address port prefix ipv6"
b" accesslog errorlog certificate encoding"
)
for o in optlist.split():
val = opts.get(o, b'')
if val in (None, b''): # should check against default options instead
continue
for u in alluis:
u.setconfig(b"web", o, val, b'serve')
app = hgweb.createapp(baseui, repo, webconf)
return hgweb.httpservice(servui, app, opts)
def createservice(ui, repo, opts):
if opts[b"cmdserver"]:
return _createcmdservice(ui, repo, opts)
else:
return _createhgwebservice(ui, repo, opts)