[ISSUE #C2] Count down the queryMessage latch when the invocation fails

[zjncs]

Motivation

MQAdminImpl.queryMessage fans out one asynchronous query per broker and waits on a CountDownLatch(brokerAddrs.size()). The latch is released by the InvokeCallback (operationSucceed/operationFail), but if MQClientAPIImpl.queryMessage itself throws synchronously — e.g. RemotingConnectException/RemotingTimeoutException for an unreachable broker — no callback is ever invoked, and the catch block only logs:

} catch (Exception e) {
    log.warn("queryMessage exception", e);
}
...
boolean ok = countDownLatch.await(timeoutMillis * 4, TimeUnit.MILLISECONDS);

The caller then blocks for the full timeoutMillis * 4 window — 24 seconds with the default timeoutMillis of 6s — before getting the "no message" answer, even though the outcome was already known. Any tool/admin call that queries by key while one broker is down pays this stall.

Modifications

• Add countDownLatch.countDown(); in the catch block, releasing this broker's count exactly as the callback would have.

Verification

Fail-before (new test on unpatched code — the per-broker invoke is mocked to throw, timeoutMillis=200):

MQAdminImplTest.assertQueryMessageNotBlockedWhenInvokeThrows:192
  queryMessage should not wait for the whole latch timeout, elapsed=846

Pass-after — full MQAdminImplTest (11 existing + 1 new); the same call now returns in single-digit milliseconds:

mvn -pl client test -Dtest='MQAdminImplTest'
Tests run: 12, Failures: 0, Errors: 0, Skipped: 0

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[RockteMQ-AI]

Summary

Correct fix for a real stall — when MQClientAPIImpl.queryMessage throws synchronously (e.g. RemotingConnectException), the callback never fires and the latch is never decremented, causing the caller to block for the full timeoutMillis * 4 (24s default). Adding countDownLatch.countDown() in the catch block is the minimal correct fix. Test validates the timing improvement.

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