MSQ: Cancel workers more quickly. #16158
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Prior to this patch, when canceled, workers would keep trying to contact the controller: they would attempt to report an error, and if they were in the midst of some other call (like a counters push) they would keep trying it. This can cause cancellation to be delayed, because the controller shuts down its HTTP server before it cancels workers. Workers are then stuck retrying calls to the controller that will never succeed. The retry loops are broken when the controller gives up on them (one minute later) and exits for real. Then, the controller failure detection logic on the worker detects that the controller has failed, and the worker finally shuts down. This patch speeds up worker cancellation by bypassing communication with the controller. There is no real need for it. If the controller canceled the workers, it isn't interested in further communications from them. If the workers were canceled out-of-band, the controller can detect this through worker monitoring and report it as a WorkerFailed error.
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Prior to this patch, when canceled, workers would keep trying to contact the controller: they would attempt to report an error, and if they were in the midst of some other call (like a counters push) they would keep trying it.
This can cause cancellation to be delayed, because the controller shuts down its HTTP server before it cancels workers. Workers are then stuck retrying calls to the controller that will never succeed. The retry loops are broken when the controller gives up on them (one minute later) and exits for real. Then, the controller failure detection logic on the worker detects that the controller has failed, and the worker finally shuts down.
This patch speeds up worker cancellation by bypassing communication with the controller. There is no real need for it. If the controller canceled the workers, it isn't interested in further communications from them. If the workers were canceled out-of-band, the controller can detect this through worker monitoring and report it as a WorkerFailed error.