[jira] [Commented] (HBASE-4965) Monitor the open file descriptors and the threads counters during the unit tests

["stack (Commented) (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-4965?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13163916#comment-13163916 ] 

stack commented on HBASE-4965:
------------------------------

Where is the code N?  Should we run this in all tests for a while till we nail some of the file descriptor issues up in hadoopqa patch build?
                
> Monitor the open file descriptors and the threads counters during the unit tests
> --------------------------------------------------------------------------------
>
>                 Key: HBASE-4965
>                 URL: https://issues.apache.org/jira/browse/HBASE-4965
>             Project: HBase
>          Issue Type: Improvement
>          Components: test
>    Affects Versions: 0.94.0
>         Environment: all
>            Reporter: nkeywal
>            Assignee: nkeywal
>            Priority: Minor
>
> We're seeing a lot of issues with hadoop-qa related to threads or file descriptors.
> Monitoring these counters would ease the analysis.
> Note as well that
>  - if we want to execute the tests in the same jvm (because the test is small or because we want to share the cluster) we can't afford to leak too many resources
>  - if the tests leak, it's more difficult to detect a leak in the software itself.
> I attach piece of code that I used. It requires two lines in a unit test class to:
> - before every test, count the threads and the open file descriptor
> - after every test, compare with the previous value.
> I ran it on some tests; we have for example:
> - client.TestMultiParallel#testBatchWithManyColsInOneRowGetAndPut: 232 threads (was 231), 390 file descriptors (was 390). => TestMultiParallel uses 232 threads!
> - client.TestMultipleTimestamps#testWithColumnDeletes: 152 threads (was 151), 283 file descriptors (was 282).
> - client.TestAdmin#testCheckHBaseAvailableClosesConnection: 477 threads (was 294), 815 file descriptors (was 461)
> - client.TestMetaMigrationRemovingHTD#testMetaMigration: 149 threads (was 148), 310 file descriptors (was 307).
> It's not always leaks, we can expect some pooling effects. But still...

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