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Is there a race condition when a lock is released?
See original GitHub issueConsider a situation with two processes:
- Process 1 currently holds a lock.
- Process 2 is waiting for
BLPOPto return.
Now, suppose that the following sequence of events unfolds:
- Process 1 executes the
UNLOCKscript to release the lock. - Process 2’s
BLPOPreturns. - Before Process 2 can call
SETNX, Process 3 callsSETNX, thereby jumping to the front of the queue and making Process 2 very cross indeed.
Am I thinking about this correctly, or is this not actually possible?
Issue Analytics
- State:
- Created 6 years ago
- Comments:8 (5 by maintainers)
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Maybe there’s a way using redis streams but I have to wonder if this is worth fixing.
If anyone wants to take a stab there’s the https://github.com/ionelmc/python-redis-lock/tree/race-on-unlock branch with a test for this.
Actually scratch that, llen would most always be 0 (an element is added there on unlock).
I don’t really think I can fix this …