Files
zulip/zerver/lib/context_managers.py
Tim Abbott e111a2f9a5 [manual] Rename Django app from zephyr to zerver.
This needs to be deployed to both staging and prod at the same
off-peak time (and the schema migration run).

At the time it is deployed, we need to make a few changes directly in
the database:

(1) UPDATE django_content_type set app_label='zerver' where app_label='zephyr';
(2) UPDATE south_migrationhistory set app_name='zerver' where app_name='zephyr';

(imported from commit eb3fd719571740189514ef0b884738cb30df1320)
2013-08-06 07:39:36 -04:00

39 lines
1.1 KiB
Python

"""
Context managers, i.e. things you can use with the 'with' statement.
"""
from __future__ import absolute_import
import fcntl
from os import path
from contextlib import contextmanager
@contextmanager
def flock(lockfile, shared=False):
"""Lock a file object using flock(2) for the duration of a 'with' statement.
If shared is True, use a LOCK_SH lock, otherwise LOCK_EX."""
fcntl.flock(lockfile, fcntl.LOCK_SH if shared else fcntl.LOCK_EX)
try:
yield
finally:
fcntl.flock(lockfile, fcntl.LOCK_UN)
@contextmanager
def lockfile(filename, shared=False):
"""Lock a file using flock(2) for the duration of a 'with' statement.
If shared is True, use a LOCK_SH lock, otherwise LOCK_EX.
The file is given by name and will be created if it does not exist."""
if not path.exists(filename):
with open(filename, 'w') as lock:
lock.write('0')
# TODO: Can we just open the file for writing, and skip the above check?
with open(filename, 'r') as lock:
with flock(lock, shared=shared):
yield