[jira] [Commented] (SPARK-21319) UnsafeExternalRowSorter.RowComparator memory leak

["William Kinney (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SPARK-21319?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16308566#comment-16308566 ] 

William Kinney commented on SPARK-21319:
----------------------------------------

Is there a workaround for this for version 2.2.0?

> UnsafeExternalRowSorter.RowComparator memory leak
> -------------------------------------------------
>
>                 Key: SPARK-21319
>                 URL: https://issues.apache.org/jira/browse/SPARK-21319
>             Project: Spark
>          Issue Type: Bug
>          Components: SQL
>    Affects Versions: 2.0.0, 2.1.0, 2.2.0, 2.3.0
>            Reporter: James Baker
>            Assignee: Wenchen Fan
>             Fix For: 2.3.0
>
>         Attachments: 0001-SPARK-21319-Fix-memory-leak-in-UnsafeExternalRowSort.patch, hprof.png
>
>
> When we wish to sort within partitions, we produce an UnsafeExternalRowSorter. This contains an UnsafeExternalSorter, which contains the UnsafeExternalRowComparator.
> The UnsafeExternalSorter adds a task completion listener which performs any additional required cleanup. The upshot of this is that we maintain a reference to the UnsafeExternalRowSorter.RowComparator until the end of the task.
> The RowComparator looks like
> {code:java}
>   private static final class RowComparator extends RecordComparator {
>     private final Ordering<InternalRow> ordering;
>     private final int numFields;
>     private final UnsafeRow row1;
>     private final UnsafeRow row2;
>     RowComparator(Ordering<InternalRow> ordering, int numFields) {
>       this.numFields = numFields;
>       this.row1 = new UnsafeRow(numFields);
>       this.row2 = new UnsafeRow(numFields);
>       this.ordering = ordering;
>     }
>     @Override
>     public int compare(Object baseObj1, long baseOff1, Object baseObj2, long baseOff2) {
>       // TODO: Why are the sizes -1?
>       row1.pointTo(baseObj1, baseOff1, -1);
>       row2.pointTo(baseObj2, baseOff2, -1);
>       return ordering.compare(row1, row2);
>     }
> }
> {code}
> which means that this will contain references to the last baseObjs that were passed in, and without tracking them for purposes of memory allocation.
> We have a job which sorts within partitions and then coalesces partitions - this has a tendency to OOM because of the references to old UnsafeRows that were used during the sorting.
> Attached is a screenshot of a memory dump during a task - our JVM has two executor threads.
> It can be seen that we have 2 references inside of row iterators, and 11 more which are only known in the task completion listener or as part of memory management.



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