chickenchickenlove opened a new pull request, #22204:
URL: https://github.com/apache/kafka/pull/22204
### Description
In `RPCProducerIDManager`, there was a race condition between
`maybeRequestNextBlock()` and `handleUnsuccessfulResponse()`, which may be
called by different threads. This race condition could leat to a premature
retry. To fix this issue, this patch reorders the operation in
`maybeRequestNextBlock()`.
### Considered parts.
- It is difficult to add a unit test for this diff because the race
condition cannot be controlled deterministically without relying on scheduling.
Instead of adding a unit test, I added comments to the paired methods to
clarify the intended ordering and concurrency assumptions.
- Race condition between `if (nextProducerIdBlock.get() != null)`and `if
(!requestInFlight.compareAndSet(false, true))`
- After `if (nextProducerIdBlock.get() != null)` is checked, another
thread may set `nextProducerIdBlock`. However, this does not cause a premature
retry. In `sanityCheckResponse(...)`, the thread only sets
`nextProducerIdBlock` and does not update `requestInFlight`. Therefore, CAS in
`maybeRequestNextBlock()`will will fail, and a premature retry will not occur.
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