[jira] [Commented] (HBASE-26336) RegionServer leaks DFSInputStreams due to not closing region after warmup

["Bryan Beaudreault (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HBASE-26336?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17425758#comment-17425758 ] 

Bryan Beaudreault commented on HBASE-26336:
-------------------------------------------

Note: I got around this leak in HDFS-16262 by using a WeakHashMap, so there is no real urgency here but it might still be worth considering how to ensure we aren't leaving un-closed DFSInputStreams.

> RegionServer leaks DFSInputStreams due to not closing region after warmup
> -------------------------------------------------------------------------
>
>                 Key: HBASE-26336
>                 URL: https://issues.apache.org/jira/browse/HBASE-26336
>             Project: HBase
>          Issue Type: Bug
>            Reporter: Bryan Beaudreault
>            Assignee: Bryan Beaudreault
>            Priority: Minor
>
> I'm working on HDFS-16262, in which we add tracking of DFSInputStreams. The DFSInputStreams are registered on creation and de-registered on call to close(). As part of testing I noticed that extra DFSInputStreams were being created and never closed. I tracked it down to HBASE-15441 in which the r.close() was removed here: [https://github.com/apache/hbase/blob/master/hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/HRegion.java#L7480]
> This has not been a huge issue because DFSInputStreams don't currently keep resources unless you do a non-positional read or use extended read buffers. So for the warmup case, the DFSInputStream is created and then eventually GC'd.
> That said, the contract of a Closeable is typically that you should close them to release resources. So we're kind of lucking out that it's not strictly necessary until you do a read, and that could change at any time (like in HDFS-16262).
> I think we should either add back a call to r.close(), or maybe it's possible to skip creating the Reader altogether for warmup. It doesn't look like the reader itself is necessary for warmup, but I could be missing something.



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