crazywen opened a new pull request, #1213:
URL: https://github.com/apache/rocketmq-clients/pull/1213
## Motivation
When using `SimpleConsumer` with long-polling, if message distribution
across queues
is uneven (some queues empty, others with messages), the consumer gets
blocked by
long-polling on empty queues, causing significant delay in receiving
messages from
queues that actually have data.
This is especially problematic in production with multiple queues where
message
traffic is bursty.
## Modification
Enhanced `SubscriptionLoadBalancer` with empty-queue skip scheduling:
- After each `receiveMessage` call, the result (empty or not) is fed back
to the
`SubscriptionLoadBalancer` via `markEmptyResult()`/`markNonEmptyResult()`
- Queues that consecutively return empty are temporarily skipped in
`takeMessageQueue()`
- Skip duration is proportional to consecutive empty count (capped at 1000
rounds)
- When a queue returns messages again, its empty counter resets immediately
- Uses `AtomicIntegerFieldUpdater` for thread-safe state updates
- Fully backward-compatible: no API changes, no configuration required
## Result
- Queues with messages are polled more frequently
- Overall message reception latency reduced in uneven-distribution
scenarios
- Zero overhead when all queues have messages (skip map stays empty)
- Added unit tests for `SubscriptionLoadBalancer`
## Type
- [x] Enhancement
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