Panic if InitiateHeartbeat exhausts retries to avoid looping infinitely #1574
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Based on experience, if the writer database fails inbeetween the copy & cutover stages (e.g. during cutover pause), the heartbeat writes will fail and stop, then leading to throttled state and an infinite loop of throttler.shouldThrottle(). Since this state is irrecoverable, make the heartbeat writer panic if retries are exhausted, so that the migration can fail and be restarted later.
grodowski
requested review from
rashiq,
meiji163 and
timvaillancourt
as code owners
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Pull Request Overview
This PR addresses an infinite loop issue in gh-ost where heartbeat write failures during database unavailability lead to unrecoverable throttled states. The change makes the heartbeat writer panic when retries are exhausted, allowing the migration to fail and be restarted later instead of looping indefinitely.
- Adds panic mechanism when heartbeat injection fails after exhausting retries
- Prevents infinite throttling loops during database failures between copy and cutover stages
| @@ -574,6 +574,7 @@ func (this *Applier) InitiateHeartbeat() { | |||
| continue | |||
| } | |||
| if err := injectHeartbeat(); err != nil { | |||
| this.migrationContext.PanicAbort <- fmt.Errorf("injectHeartbeat writing failed %d times, last error: %w", numSuccessiveFailures, err) | |||
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The variable numSuccessiveFailures is referenced but not visible in this diff. Ensure this variable is properly defined and incremented in the retry logic to accurately reflect the number of failures.
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Based on experience, if the writer database fails inbeetween the copy & cutover stages (e.g. during cutover pause), the heartbeat writes will fail and stop, then leading to throttled state and an infinite loop of
throttler.shouldThrottle().Since this state is irrecoverable, make the heartbeat writer panic if retries are exhausted, so that the migration can fail and be restarted later.
We've tested this in production now without issues, but if there's some desired behaviour that this PR changes, we might consider adding a new CLI option to control it - feedback welcome.
Closes #1569 (issue has some more context too)
script/cibuildreturns with no formatting errors, build errors or unit test errors.