cinder.coordination module¶
Coordination and locking utilities.
-
class
Coordinator
(agent_id=None, prefix='')¶ Bases:
object
Tooz coordination wrapper.
Coordination member id is created from concatenated prefix and agent_id parameters.
- Parameters
agent_id (str) – Agent identifier
prefix (str) – Used to provide member identifier with a meaningful prefix.
-
get_lock
(name)¶ Return a Tooz backend lock.
- Parameters
name (str) – The lock name that is used to identify it across all nodes.
-
start
()¶
-
stop
()¶ Disconnect from coordination backend and stop heartbeat.
-
synchronized
(lock_name, blocking=True, coordinator=<cinder.coordination.Coordinator object>)¶ Synchronization decorator.
- Parameters
lock_name (str) – Lock name.
blocking – If True, blocks until the lock is acquired. If False, raises exception when not acquired. Otherwise, the value is used as a timeout value and if lock is not acquired after this number of seconds exception is raised.
coordinator – Coordinator class to use when creating lock. Defaults to the global coordinator.
- Raises
tooz.coordination.LockAcquireFailed – if lock is not acquired
Decorating a method like so:
@synchronized('mylock') def foo(self, *args): ...
ensures that only one process 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.
Lock name can be formatted using Python format string syntax:
@synchronized('{f_name}-{vol.id}-{snap[name]}') def foo(self, vol, snap): ...
Available field names are: decorated function parameters and f_name as a decorated function name.