Mercurial > hg
view hgext/remotefilelog/extutil.py @ 42783:c8d3af9c7e65
perf: handle NameError for `pycompat.foo` when pycompat wasn't imported
On old Mercurial versions, we won't have a pycompat variable defined,
and then `pycompat.foo` will raise a NameError.
Differential Revision: https://phab.mercurial-scm.org/D6743
author | Martin von Zweigbergk <martinvonz@google.com> |
---|---|
date | Mon, 19 Aug 2019 10:38:38 -0700 |
parents | 3fbfbc8c9f82 |
children |
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# 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)