[GitHub] [zookeeper] maoling opened a new pull request #1024: ZOOKEEPER-3470:Flaky test: LearnerMetricsTest.testLearnerMetricsTest()

[GitBox <gi...@apache.org>]

maoling opened a new pull request #1024: ZOOKEEPER-3470:Flaky test: LearnerMetricsTest.testLearnerMetricsTest()
URL: https://github.com/apache/zookeeper/pull/1024
 
 
   - From the logs, we can guess that this flaky test was caused from the observer is lagged behind the leader. we can inject the delay in the following codes:`Observer#processPacket` to reproduce this issue:
   ```
          case Leader.INFORM:
               **Thread.sleep(250);**
               ServerMetrics.getMetrics().LEARNER_COMMIT_RECEIVED_COUNT.add(1);
               TxnHeader hdr = new TxnHeader();
   ```
   - we may have no efficient way to have a hook to make sure that the create request has applied in all the participants successfully, but we can assert the size relation: the actual metric value is alway lessThanOrEqualTo the expected value because the delay between learns and leader. 
   - more details in the [ZOOKEEPER-3470](https://issues.apache.org/jira/browse/ZOOKEEPER-3470) 

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