fix(profiling): Race condition spawning multiple profiling threads #1676
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There is a race condition where multiple profiling threads may be spawned. Specifically, if `start_profiling` is called immediately after `stop_profiling`. This happens because `stop_profiling` does not immediately terminate the thread, instead the thread will check that the event was set and exit at the end of the current iteration. If `start_profiling` is called during the iteration, the event gets set again and the old thread will continue running. To fix this, a new event is created when a profiling thread starts so they can be terminated independently.
sentry_sdk/profiler.py
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| # make sure to clear the event as we reuse the same event | ||
| # over the lifetime of the scheduler | ||
| self.event.clear() | ||
| event = threading.Event() | ||
| self.threads.put_nowait(event) |
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just nitpicking but could we possibly have a better name than threads?
Maybe signify purpose, like termination_events/stop_events or something since we use them to break the profiler loops?
sl0thentr0py
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Oct 13, 2022
Zylphrex
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This is fixing a mistake from #1676, and adding a sample at the start of the profile instead of waiting 1 interval before getting the first sample.
Zylphrex
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This is fixing a mistake from #1676, and adding a sample at the start of the profile instead of waiting 1 interval before getting the first sample.
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There is a race condition where multiple profiling threads may be spawned. Specifically, if
start_profilingis called immediately afterstop_profiling. This happens becausestop_profilingdoes not immediately terminate the thread, instead the thread will check that the event was set and exit at the end of the current iteration. Ifstart_profilingis called during the iteration, the event gets set again and the old thread will continue running. To fix this, a new event is created when a profiling thread starts so they can be terminated independently.