This is an archive of the discontinued Mercurial Phabricator instance.

	# extutil.py - useful utility methods for extensions
	#
	# Copyright 2016 Facebook
	#
	# 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 contextlib
	import errno
	import os
	import time

	from mercurial import (
	error,
	lock as lockmod,
	util,
	vfs as vfsmod,
	)

	@contextlib.contextmanager
	def flock(lockpath, description, timeout=-1):
	"""A flock based lock object. Currently it is always non-blocking.

	Note that since it is flock based, you can accidentally take it multiple
	times within one process and the first one to be released will release all
	of them. So the caller needs to be careful to not create more than one
	instance per lock.
	"""

	# best effort lightweight lock
	try:
	import fcntl
	fcntl.flock
	except ImportError:
	# fallback to Mercurial lock
	vfs = vfsmod.vfs(os.path.dirname(lockpath))
	with lockmod.lock(vfs, os.path.basename(lockpath), timeout=timeout):
	yield
	return
	# make sure lock file exists
	util.makedirs(os.path.dirname(lockpath))
	with open(lockpath, 'a'):
	pass
	lockfd = os.open(lockpath, os.O_RDONLY, 0o664)
	start = time.time()
	while True:
	try:
	fcntl.flock(lockfd, fcntl.LOCK_EX \| fcntl.LOCK_NB)
	break
	except IOError as ex:
	if ex.errno == errno.EAGAIN:
	if timeout != -1 and time.time() - start > timeout:
	raise error.LockHeld(errno.EAGAIN, lockpath, description,
	'')
	else:
	time.sleep(0.05)
	continue
	raise

	try:
	yield
	finally:
	fcntl.flock(lockfd, fcntl.LOCK_UN)
	os.close(lockfd)

remotefilelog: remove dead code for using flock() for lockingClosedPublic