Fix race condition in worker restart causing spawn failure #3086
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Fixes sanic-org#3055 During worker restart, a race condition occurs between WorkerProcess.restart() and WorkerManager._sync_states() that causes the restart to fail with: "Cannot spawn a worker process until it is idle." The race condition happens when: 1. WorkerProcess.restart() sets state to RESTARTING and terminates the process 2. WorkerManager._sync_states() runs concurrently, sees process is not alive 3. _sync_states() changes state from RESTARTING to COMPLETED 4. WorkerProcess.restart() tries to spawn(), but state is now COMPLETED 5. spawn() raises exception because state is not IDLE or RESTARTING The fix prevents _sync_states() from changing the state of processes that are in the RESTARTING state, allowing the restart flow to complete without interference. Changes: - Added check in _sync_states() to skip processes with state RESTARTING - This prevents the race condition by ensuring restart flow is not interrupted - Safe change: RESTARTING is temporary, managed entirely by restart() method - No performance impact: just one additional state check per process
ahopkins
approved these changes
Oct 23, 2025
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Fixes #3055
During worker restart, a race condition occurs between WorkerProcess.restart() and WorkerManager._sync_states() that causes the restart to fail with: "Cannot spawn a worker process until it is idle."
The race condition happens when:
The fix prevents _sync_states() from changing the state of processes that are in the RESTARTING state, allowing the restart flow to complete without interference.
Changes: