[jira] [Created] (HBASE-25598) TestFromClientSide5.testScanMetrics is flaky

["Sun Xin (Jira)" <ji...@apache.org>]

Sun Xin created HBASE-25598:
-------------------------------

             Summary: TestFromClientSide5.testScanMetrics is flaky
                 Key: HBASE-25598
                 URL: https://issues.apache.org/jira/browse/HBASE-25598
             Project: HBase
          Issue Type: Bug
    Affects Versions: 2.4.1, 2.3.4, 3.0.0-alpha-1
            Reporter: Sun Xin
            Assignee: Sun Xin


In some PRs, I got the following errors in UT results.
{code:java}
[ERROR] Errors: 
[ERROR] org.apache.hadoop.hbase.client.TestFromClientSide5.testScanMetrics[0]
[ERROR]   Run 1: TestFromClientSide5.testScanMetrics:1018 Did not count the result bytes expected:<60> but was:<120>
[ERROR]   Run 2: TestFromClientSide5.testScanMetrics:1036 Did not count the result bytes expected:<60> but was:<180>
[ERROR]   Run 3: TestFromClientSide5.testScanMetrics:951 » MasterRegistryFetch Exception making...
[INFO] 
[ERROR] org.apache.hadoop.hbase.client.TestFromClientSideWithCoprocessor5.testScanMetrics[1]
[ERROR]   Run 1: TestFromClientSideWithCoprocessor5>TestFromClientSide5.testScanMetrics:1036 Did not count the result bytes expected:<60> but was:<120>
[ERROR]   Run 2: TestFromClientSideWithCoprocessor5>TestFromClientSide5.testScanMetrics:951 » IO
[ERROR]   Run 3: TestFromClientSideWithCoprocessor5>TestFromClientSide5.testScanMetrics:951 » IO
[INFO] 
{code}
I read the code further and found that this UT is flaky.
{code:java}
// check byte counters
scan2 = new Scan();
scan2.setScanMetricsEnabled(true);
scan2.setCaching(1);
try (ResultScanner scanner = ht.getScanner(scan2)) {
  int numBytes = 0;
  for (Result result : scanner.next(1)) {
    for (Cell cell : result.listCells()) {
      numBytes += PrivateCellUtil.estimatedSerializedSizeOf(cell);
    }
  }
  scanner.close();
  ScanMetrics scanMetrics = scanner.getScanMetrics();
  assertEquals("Did not count the result bytes", numBytes,
          scanMetrics.countOfBytesInResults.get());
}
{code}
In the code above, it is to check scanMetrics.countOfBytesInResults, but just get only ONE row by scanner.next(1) . A total of 3 rows are inserted into the table, and scanner prefetch from server in advance until maxCacheSize is exceeded, see [here|https://github.com/apache/hbase/blob/5fa15cfde3d77e77ffb1f09d60dce4db264f3831/hbase-client/src/main/java/org/apache/hadoop/hbase/client/AsyncTableResultScanner.java#L94].

So if scanner prefetch more than one row before closing scanner, the UT fails. we can reproduce this problem steadily by sleeping before scanner.close().



--
This message was sent by Atlassian Jira
(v8.3.4#803005)