fix: retry middleware corrupts exponential backoff state#690
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… in operation function The Retry middleware's operation function called expBackoff.NextBackOff() inside ShouldRetry and OnRetryHook callbacks, which advanced the exponential backoff's internal state machine. When backoff.Retry then called NextBackOff() to determine the actual sleep duration, it received a future interval, effectively skipping one or more intermediate delays. For example, with InitialInterval=10ms, Multiplier=2.0, the sequence of actual sleep durations was: 20ms, 40ms, 80ms, 160ms instead of the correct: 10ms, 20ms, 40ms, 80ms. The fix computes the approximate delay from the retry configuration without mutating any backoff state, preserving the correct exponential backoff sequence used by the backoff.Retry framework. Signed-off-by: Abdulazez A. <[email protected]>
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Bug
The Retry middleware in
message/router/middleware/retry.gocorrupts the exponential backoff state machine by callingexpBackoff.NextBackOff()inside theoperationfunction.Root Cause
The
operationfunction passed tobackoff.Retry()was callingexpBackoff.NextBackOff()for two purposes:ShouldRetrycallbackOnRetryHookcallbackEach call to
NextBackOff()advances the backoff's internal state. Whenbackoff.Retry()itself then callsNextBackOff()to determine the actual sleep duration, it receives a future interval.Impact
Retry delays were double what they should be. With
InitialInterval=10ms,Multiplier=2.0:Fix
Replaced
NextBackOff()calls with a new pure functioncomputeBackoffDelay_atRetryNum()that computes the approximate delay from the config parameters without mutating any state. This letsbackoff.Retry()continue to drive actual sleep durations correctly.Test Results
All existing tests pass (
go test ./...— all green).Fixes #224 (partial)