A simple XML-RPC-based lock daemon to support fencing.
Using the lockd API
lockd provides a light-weight implementation of a locking mechanism for long-running resources by maintaining lock files in a given directory.
>>> import tempfile >>> lockdir = tempfile.mkdtemp() >>> from gocept.lockd.lockd import Lockd >>> daemon = Lockd(lockdir)
Resources are identified by a string and clients performing the lock are identified by another string:
>>> daemon.lock('resource1', 'client1')
Once a resource is locked, it can not be locked again:
>>> daemon.lock('resource1', 'client2') Traceback (most recent call last): Exception: Resource already locked by 'client1'
However, other resources can be locked in parallel:
>>> daemon.lock('resource2', 'client2')
Clients, other than the client who locked a resource, can not unlock it:
>>> daemon.unlock('resource1', 'client2') Traceback (most recent call last): Exception: Resource locked by 'client1' cannot be unlocked by 'client2'
The client, who locked the resource, can unlock it again:
>>> daemon.unlock('resource1', 'client1')
Once unlocked, it can not be unlocked a second time:
>>> daemon.unlock('resource1', 'client1') Traceback (most recent call last): Exception: Resource not locked
IMPORTANT security note
Resource identification and client authorization are out of scope for lockd. It should only be used and exposed within a trusted environment.
>>> import shutil >>> shutil.rmtree(lockdir)