Fix a rare deadlock in scanner.Stop #3818
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dnr
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Jan 20, 2023
Co-authored-by: David Reiss <david@temporal.io>
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What changed?
I modified the Stop() method of our scanners to cancel running attempts to start workflows.
Why?
I did this because it fixes a race condition which often occurs when the server is shutdown soon after starting. When the server is shutdown, the scanner may still be trying
startWorkflow. This method utilizes an SDK client. However, when the server shutdown all of its services, it may shutdown the frontend handler before the scanner. As a result, all calls to the SDK client will fail, causing startWorkflow to fail. Currently, we retry startWorkflow a lot, so the scanner can currently enter a long-running retry loop. To fix this, we now cancel the retries as soon as the scanner is shutdown.How did you test it?
I added a test case which simulates the setup described above.
Potential risks
We may see some more error logs about SDK requests being canceled when servers are started/stopped.
Is hotfix candidate?
No.