[Bug] Bare lock busy-wait without yield in ack/changeInvisibleTime processors pins ack executor threads

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@messere1 がすでに取り組んでいます。

2026年10月12日 から。

  • #11384 @messere1 による — オープン

評価

難易度
2/5
見積もり時間
1〜3時間
初心者へのやさしさ
35/100
issue の種類
バグ
明瞭さ
明確に書かれている
活発さ
停滞
技術スタック
java
領域
backend, distributed-systems

調査の方向性

Read the listed lock loops in AckMessageProcessor.java and ChangeInvisibleTimeProcessor.java, then compare them with PopConsumerService#tryLockForPop and the ackMessageExecutor registration in BrokerController.java. Check the linked pull request #11384 for current work. Done means the listed contended paths yield while preserving their lock behavior.

索引モデルが issue の本文から書いたものです。

説明

Before Creating the Bug Report
  • I found a bug. The issue list contains no issue matching my bug.
Your Environment
  • RocketMQ version: 5.4.x (current develop)
Describe the Bug

Several pop/ack paths acquire the consumer/queue lock with a bare busy-wait that has no Thread.yield():

  • AckMessageProcessor#ackOrderly — while (!queueLockManager.tryLock(lockKey)) {} (broker/src/main/java/org/apache/rocketmq/broker/processor/AckMessageProcessor.java:405)
  • AckMessageProcessor#ackOrderly (KV service path) — while (!consumerLockService.tryLock(consumeGroup, topic)) {} (AckMessageProcessor.java:448)
  • AckMessageProcessor#ackLite — while (!consumerLockService.tryLock(lockKey)) {} (AckMessageProcessor.java:538)
  • ChangeInvisibleTimeProcessor#changeInvisibilityDuration — same shape (ChangeInvisibleTimeProcessor.java:203, :235, :389)

All of these are registered on the shared ackMessageExecutor (BrokerController.java:1204-1213), so each contending request pins one worker thread at 100% CPU for the entire contention window:

  1. Under a (group, topic) contention burst, several executor workers can be stuck spinning at once, cutting the executor's effective parallelism for every other ack / changeInvisibleTime request on the broker.
  2. On core-saturated brokers the spinning threads compete for CPU with the very lock holders that must finish for the spin to exit, extending the wait beyond the actual critical-section length.

The codebase already establishes the correct pattern for this lock service: PopConsumerService#tryLockForPop (added by #10828) spins with Thread.yield() and a comment explaining why the spin is kept — same consumerLockService, same contention shape, but it yields.

Steps to Reproduce

Code inspection + any workload where two consumers of the same group ack/changeInvisibleTime concurrently for the same topic: the losing request's thread spins in the while loop with no yield until the holder releases (or PopConsumerLockService.removeTimeout() self-heals a stale entry).

What Did You Expect to See?

The spin semantics preserved (these paths must hold the lock to commit offsets atomically) but with Thread.yield() in the loop, matching tryLockForPop — so a contending worker yields its core to the holder instead of burning it.

Additional Context

None

主要言語
Java
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4日 20時間
マージ済み PR（30日）
11

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