The nova.openstack.common.lockutils Module

InterProcessLock

alias of _PosixLock

synchronized(name, lock_file_prefix, external=False, lock_path=None)

Synchronization decorator.

Decorating a method like so:

@synchronized('mylock')
def foo(self, *args):
   ...

ensures that only one thread will execute the foo method at a time.

Different methods can share the same lock:

@synchronized('mylock')
def foo(self, *args):
   ...

@synchronized('mylock')
def bar(self, *args):
   ...

This way only one of either foo or bar can be executing at a time.

The lock_file_prefix argument is used to provide lock files on disk with a meaningful prefix. The prefix should end with a hyphen (‘-‘) if specified.

The external keyword argument denotes whether this lock should work across multiple processes. This means that if two different workers both run a a method decorated with @synchronized(‘mylock’, external=True), only one of them will execute at a time.

The lock_path keyword argument is used to specify a special location for external lock files to live. If nothing is set, then CONF.lock_path is used as a default.