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From "Paul Rogers (JIRA)" <j...@apache.org>
Subject [jira] [Created] (DRILL-5210) External Sort BatchGroup leaks memory if an OOM occurs during read
Date Sat, 21 Jan 2017 19:36:27 GMT
Paul Rogers created DRILL-5210:
----------------------------------

             Summary: External Sort BatchGroup leaks memory if an OOM occurs during read
                 Key: DRILL-5210
                 URL: https://issues.apache.org/jira/browse/DRILL-5210
             Project: Apache Drill
          Issue Type: Bug
    Affects Versions: 1.9.0
            Reporter: Paul Rogers
            Assignee: Paul Rogers


The External Sort operator (batch) can spill to disk when it runs out of memory. To do so,
it uses a class called {{BatchGroup}}. Later, when the sort merges spilled runs, {{BatchGroup}}
reads the run back into memory one batch at a time.

If an OOM error occurs during the read operation, the partially-read batches leak: they are
not released. The fragment executor then issues a memory leak error while shutting down the
query.

This error has probably not been caught until now because the {{BatchGroup}} code does not
make use of the fault injector. Elsewhere in the external sort, we use the fault injector
to insert a (simulated) OOM exception so we can determine if clean-up occurs properly. No
such fault injection code exists in {{BatchGroup}}.



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