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https://issues.apache.org/jira/browse/HBASE-25598?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Sun Xin resolved HBASE-25598.
-----------------------------
Fix Version/s: 2.4.2
2.3.5
2.2.7
3.0.0-alpha-1
Resolution: Fixed
Thanks [~zhangduo] for reviewing.
Merged to master and all active branch-2.x.
> TestFromClientSide5.testScanMetrics is flaky
> --------------------------------------------
>
> Key: HBASE-25598
> URL: https://issues.apache.org/jira/browse/HBASE-25598
> Project: HBase
> Issue Type: Bug
> Affects Versions: 3.0.0-alpha-1, 2.3.4, 2.4.1
> Reporter: Sun Xin
> Assignee: Sun Xin
> Priority: Major
> Fix For: 3.0.0-alpha-1, 2.2.7, 2.3.5, 2.4.2
>
>
> 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().
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