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50 lines
1.4 KiB
50 lines
1.4 KiB
6 years ago
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locket.py
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=========
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Locket implements a lock that can be used by multiple processes provided they use the same path.
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.. code-block:: python
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import locket
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# Wait for lock
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with locket.lock_file("path/to/lock/file"):
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perform_action()
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# Raise error if lock cannot be acquired immediately
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with locket.lock_file("path/to/lock/file", timeout=0):
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perform_action()
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# Raise error if lock cannot be acquired after thirty seconds
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with locket.lock_file("path/to/lock/file", timeout=30):
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perform_action()
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# Without context managers:
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lock = locket.lock_file("path/to/lock/file")
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try:
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lock.acquire()
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perform_action()
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finally:
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lock.release()
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Locks largely behave as (non-reentrant) `Lock` instances from the `threading`
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module in the standard library. Specifically, their behaviour is:
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* Locks are uniquely identified by the file being locked,
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both in the same process and across different processes.
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* Locks are either in a locked or unlocked state.
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* When the lock is unlocked, calling `acquire()` returns immediately and changes
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the lock state to locked.
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* When the lock is locked, calling `acquire()` will block until the lock state
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changes to unlocked, or until the timeout expires.
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* If a process holds a lock, any thread in that process can call `release()` to
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change the state to unlocked.
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* Behaviour of locks after `fork` is undefined.
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