ai-yang opened a new issue, #10739:
URL: https://github.com/apache/rocketmq/issues/10739
## RocketMQ version
`develop` at `00e45b8a6db23efbe756d0306f10716156cfd4dd`
## Describe the bug
`FutureUtils.appendNextFuture` ignores the dependent stage returned by
`whenCompleteAsync`. If the supplied executor rejects the completion task,
that
dependent stage completes exceptionally but the manually created `nextFuture`
is never completed.
The production executors used by `ProducerProcessor` and `ConsumerProcessor`
add a second failure mode. They are created through the default
`ThreadPoolMonitor.createAndMonitor` overload, whose rejection handler is
`DiscardOldestPolicy`. After shutdown it silently discards the completion
task;
under saturation it can silently discard an older queued completion task.
Neither case gives `FutureUtils` a rejection that it can propagate, so a
proxy
request future can remain pending indefinitely.
## Deterministic reproduction
Two synchronous regression tests reproduce the complete failure chain on JDK
8.
### 1. Rejection is not propagated by `FutureUtils`
1. Create a single-thread executor and shut it down.
2. Call `FutureUtils.addExecutor(CompletableFuture.completedFuture("value"),
executor)`.
3. Inspect the returned future.
Expected: the returned future is completed exceptionally with the scheduling
failure.
Actual: the stage returned by `whenCompleteAsync` is exceptional, but the
stage
is ignored and the returned `nextFuture` remains pending.
The controlled test
`FutureUtilsTest#testAddExecutorCompletesExceptionallyWhenExecutorRejectsTask`
failed at the expected `result.isDone()` assertion in 5/5 runs.
### 2. The actual Proxy processor executor silently drops the task
1. Construct `DefaultMessagingProcessor` with its real producer and consumer
processor executors.
2. Shut down the producer processor executor.
3. Pass that executor to `FutureUtils.addExecutor` with an already completed
source future.
4. Inspect the returned future.
Expected: rejection is observable and the returned future is completed
exceptionally.
Actual: `DiscardOldestPolicy` silently discards the task after shutdown and
the
returned future remains pending.
The controlled test
`DefaultMessagingProcessorTest#testProcessorFutureCompletesWhenExecutorIsShutDown`
failed at the expected `result.isDone()` assertion in 5/5 runs. It uses the
actual processor pool, no sleeps, randomized scheduling, network access, or
external service.
## Impact
`FutureUtils.addExecutor` is used by the Proxy `ProducerProcessor` and
`ConsumerProcessor` request paths. During processor-pool shutdown, or when
the
bounded pool rejects completion work, callers may receive a future that never
reaches a terminal state. This can leave gRPC/remoting requests waiting
until an
outer timeout or connection teardown instead of receiving an immediate
failure.
## Suggested fix
Both parts are needed; either one alone leaves a pending-future path:
- Retain the stage returned by `whenCompleteAsync` and propagate a scheduling
failure into `nextFuture`.
- Create the producer and consumer processor executors with an explicit
throwing rejection policy (for example `AbortPolicy`) instead of the
default
silent `DiscardOldestPolicy`, so `FutureUtils` can observe both shutdown
and
overload rejection.
- Add regression coverage for both a throwing executor and the actual Proxy
processor executor after shutdown.
This changes only internal completion/rejection behavior and does not change
a
public protocol.
## Related work checked
- #8900 contains a `FutureUtils` stack frame but reports client cancellation
and
message redelivery, not executor rejection or a pending returned future.
- #9253 concerns receipt-handle renewal after client disconnection, not
completion-task rejection.
- #5575 introduced the Proxy remoting implementation and is not a fix for
this
behavior.
- #10711 concerns unsupported metadata futures and does not modify
`FutureUtils` or the processor executor policies.
Searches across open and closed issues and pull requests for `FutureUtils`,
`addExecutor`, `DefaultMessagingProcessor`, `DiscardOldestPolicy`, executor
shutdown/rejection, and pending Proxy futures found no equivalent report or
claimed fix.
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