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fix(service): stop an unsubscribe from deadlocking the bus - #3
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Unsubscribe took the lock once per subscriber it looked at, each unlock deferred to its return: a websocket closing while it was not the first subscriber of an event locked the bus's mutex twice and never came back. Every subscription after it hung once its websocket was open, so the subscriber believed it was listening and received nothing. The core's alerts, which resubscribe each time the core restarts, hit it on every install check: three connections closed together, the third deadlocked. The lock is now taken once per call, in both services. The dispatch reads the subscriber lists under it too, as a map read while Subscribe writes it can bring the bus down. And two silent drops go: a publish waits for the dispatch instead of dropping an event it is busy with, and a subscriber may be 64 events behind instead of one.
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A websocket closing while it was not the first subscriber of an event deadlocked the bus:
Unsubscribelocked the mutex once per subscriber it looked at, each unlock deferred. Every subscription after that hung once its websocket was open, which is why the core's push alerts never receivedbackup:errorin the v0.5.10 install check.EventServiceWSandActionServiceWSTests:
TestUnsubscribeASubscriberAfterTheFirstdeadlocks on the old code;TestEventsPublishedTogetherAllArrive.