[jira] [Updated] (HDFS-10275) TestDataNodeMetrics failing intermittently due to TotalWriteTime counted incorrectly

["Lin Yiqun (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/HDFS-10275?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Lin Yiqun updated HDFS-10275:
-----------------------------
    Description: 
The unit test {{TestDataNodeMetrics}} fails intermittently. The failed info show these:
{code}
Results :

Failed tests: 
  TestDataNodeVolumeFailureToleration.testVolumeAndTolerableConfiguration:195->testVolumeConfig:232 expected:<false> but was:<true>

Tests in error: 
  TestOpenFilesWithSnapshot.testWithCheckpoint:94 ? IO Timed out waiting for Min...
  TestDataNodeMetrics.testDataNodeTimeSpend:279 ? Timeout Timed out waiting for ...
  TestHFlush.testHFlushInterrupted ? IO The stream is closed
{code}
In line 279 in {{TestDataNodeMetrics}}, it takes place timed out. Then I looked into the code and found the real reason is that the metric of {{TotalWriteTime}} frequently count 0 in each iteration of creating file. And the this leads to retry operations till timeout.
I debug the test in my local. I found the most suspect reason which cause {{TotalWriteTime}} metric count always be 0 is that we using the {{SimulatedFSDataset}} for spending time test. In {{SimulatedFSDataset}}, it will use the inner class's method {{SimulatedOutputStream#write}} to count the write time and the method of this class just updates the {{length}} and throws its data away.
{code}
    @Override
    public void write(byte[] b,
              int off,
              int len) throws IOException  {
      length += len;
    }
{code} 
So the writing operation hardly not costs any time. So we should use a real way to create file instead of simulated way. I have tested in my local that the test is passed just one time when I delete the simulated way, while the test retries many times to count write time in old way.

  was:
The unit test {{TestDataNodeMetrics}} fails intermittently. The failed info show these:
{code}
Results :

Failed tests: 
  TestDataNodeVolumeFailureToleration.testVolumeAndTolerableConfiguration:195->testVolumeConfig:232 expected:<false> but was:<true>

Tests in error: 
  TestOpenFilesWithSnapshot.testWithCheckpoint:94 ? IO Timed out waiting for Min...
  TestDataNodeMetrics.testDataNodeTimeSpend:279 ? Timeout Timed out waiting for ...
  TestHFlush.testHFlushInterrupted ? IO The stream is closed
{code}
In line 279 in {{TestDataNodeMetrics}}, it takes place timed out. Then I looked into the code and found the real reason is that the metric of {{TotalWriteTime}} frequently count 0 in each iteration of creating file. And the this leads to retry operations till timeout.
I debug the test in my local. I found the most suspect reason whic cause {{TotalWriteTime}} metric count always be 0 is that we using the {{SimulatedFSDataset}} for spending time test. In {{SimulatedFSDataset}}, it will use the inner class's method {{SimulatedOutputStream#write}} to count the write time and the method of this class just updates the {{length}} and throws its data away.
{code}
    @Override
    public void write(byte[] b,
              int off,
              int len) throws IOException  {
      length += len;
    }
{code} 
So the writing operation hardly not costs any time. So we should use a real way to create file instead of simulated way. I have tested in my local that the test is passed just one time when I delete the simulated way, while the test retries many times to count write time in old way.


> TestDataNodeMetrics failing intermittently due to TotalWriteTime counted incorrectly
> ------------------------------------------------------------------------------------
>
>                 Key: HDFS-10275
>                 URL: https://issues.apache.org/jira/browse/HDFS-10275
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: test
>            Reporter: Lin Yiqun
>            Assignee: Lin Yiqun
>
> The unit test {{TestDataNodeMetrics}} fails intermittently. The failed info show these:
> {code}
> Results :
> Failed tests: 
>   TestDataNodeVolumeFailureToleration.testVolumeAndTolerableConfiguration:195->testVolumeConfig:232 expected:<false> but was:<true>
> Tests in error: 
>   TestOpenFilesWithSnapshot.testWithCheckpoint:94 ? IO Timed out waiting for Min...
>   TestDataNodeMetrics.testDataNodeTimeSpend:279 ? Timeout Timed out waiting for ...
>   TestHFlush.testHFlushInterrupted ? IO The stream is closed
> {code}
> In line 279 in {{TestDataNodeMetrics}}, it takes place timed out. Then I looked into the code and found the real reason is that the metric of {{TotalWriteTime}} frequently count 0 in each iteration of creating file. And the this leads to retry operations till timeout.
> I debug the test in my local. I found the most suspect reason which cause {{TotalWriteTime}} metric count always be 0 is that we using the {{SimulatedFSDataset}} for spending time test. In {{SimulatedFSDataset}}, it will use the inner class's method {{SimulatedOutputStream#write}} to count the write time and the method of this class just updates the {{length}} and throws its data away.
> {code}
>     @Override
>     public void write(byte[] b,
>               int off,
>               int len) throws IOException  {
>       length += len;
>     }
> {code} 
> So the writing operation hardly not costs any time. So we should use a real way to create file instead of simulated way. I have tested in my local that the test is passed just one time when I delete the simulated way, while the test retries many times to count write time in old way.



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