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From "Enis Soztutar (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HBASE-16032) Possible memory leak in StoreScanner
Date Tue, 21 Jun 2016 18:05:58 GMT

    [ https://issues.apache.org/jira/browse/HBASE-16032?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15342337#comment-15342337
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Enis Soztutar commented on HBASE-16032:
---------------------------------------

Belated +1. 

> Possible memory leak in StoreScanner
> ------------------------------------
>
>                 Key: HBASE-16032
>                 URL: https://issues.apache.org/jira/browse/HBASE-16032
>             Project: HBase
>          Issue Type: Bug
>    Affects Versions: 1.2.1, 1.1.5, 0.98.20
>            Reporter: Yu Li
>            Assignee: Yu Li
>             Fix For: 2.0.0, 1.1.6, 1.3.1, 0.98.21, 1.2.3
>
>         Attachments: HBASE-16032.patch, HBASE-16032_v2.patch, HBASE-16032_v3.patch, HBASE-16032_v4.patch
>
>
> We observed frequent fullGC of RS in our production environment, and after analyzing
the heapdump, we found large memory occupancy by HStore#changedReaderObservers, the map is
surprisingly containing 7500w objects...
> After some debugging, I located some possible memory leak in StoreScanner constructor:
> {code}
>   public StoreScanner(Store store, ScanInfo scanInfo, Scan scan, final NavigableSet<byte[]>
columns,
>       long readPt)
>   throws IOException {
>     this(store, scan, scanInfo, columns, readPt, scan.getCacheBlocks());
>     if (columns != null && scan.isRaw()) {
>       throw new DoNotRetryIOException("Cannot specify any column for a raw scan");
>     }
>     matcher = new ScanQueryMatcher(scan, scanInfo, columns,
>         ScanType.USER_SCAN, Long.MAX_VALUE, HConstants.LATEST_TIMESTAMP,
>         oldestUnexpiredTS, now, store.getCoprocessorHost());
>     this.store.addChangedReaderObserver(this);
>     // Pass columns to try to filter out unnecessary StoreFiles.
>     List<KeyValueScanner> scanners = getScannersNoCompaction();
>     ...
>     seekScanners(scanners, matcher.getStartKey(), explicitColumnQuery
>         && lazySeekEnabledGlobally, parallelSeekEnabled);
>     ...
>     resetKVHeap(scanners, store.getComparator());
>   }
> {code}
> If there's any Exception thrown after {{this.store.addChangedReaderObserver(this)}},
the returned scanner might be null and there's no chance to remove the scanner from changedReaderObservers,
like in {{HRegion#get}}
> {code}
>     RegionScanner scanner = null;
>     try {
>       scanner = getScanner(scan);
>       scanner.next(results);
>     } finally {
>       if (scanner != null)
>         scanner.close();
>     }
> {code}
> What's more, all exception thrown in the {{HRegion#getScanner}} path will cause scanner==null
then memory leak, so we also need to handle this part.



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