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Date: Wed, 15 May 2013 19:31:16 +0000 (UTC)
From: "Colin Patrick McCabe (JIRA)" <jira@apache.org>
To: hdfs-issues@hadoop.apache.org
Message-ID: <JIRA.12647627.1368570217397.325718.1368646276576@arcas>
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Subject: [jira] [Commented] (HDFS-4824) FileInputStreamCache.close leaves
 dangling reference to FileInputStreamCache.cacheCleaner
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    [ https://issues.apache.org/jira/browse/HDFS-4824?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13658692#comment-13658692 ] 

Colin Patrick McCabe commented on HDFS-4824:
--------------------------------------------

OK, I figured out what is going on here.  scheduleAtFixedRate is actually creating a new Runnable which wraps the one that it's passed in (cacheCleaner).  So telling the executor to remove cacheCleaner itself doesn't work, since the real runnable that was scheduled is the wrapper.

Instead, we should keep around the future which {{scheduleAtFixedRate}} returned, and call {{Future#Cancel}} on it.

Patch is attached.
                
> FileInputStreamCache.close leaves dangling reference to FileInputStreamCache.cacheCleaner
> -----------------------------------------------------------------------------------------
>
>                 Key: HDFS-4824
>                 URL: https://issues.apache.org/jira/browse/HDFS-4824
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: hdfs-client
>    Affects Versions: 2.0.4-alpha
>            Reporter: Henry Robinson
>            Assignee: Colin Patrick McCabe
>
> {{FileInputStreamCache}} leaves around a reference to its {{cacheCleaner}} after {{close()}}.
> The {{cacheCleaner}} is created like this:
> {code}
> if (cacheCleaner == null) {
>           cacheCleaner = new CacheCleaner();
>           executor.scheduleAtFixedRate(cacheCleaner, expiryTimeMs, expiryTimeMs,
>               TimeUnit.MILLISECONDS);
>         }
> {code}
> and supposedly removed like this:
> {code}
> if (cacheCleaner != null) {
>   executor.remove(cacheCleaner);
> }
> {code}
> However, {{ScheduledThreadPoolExecutor.remove}} returns a success boolean which should be checked. And I _think_ from a quick read of that class that the return value of {{scheduleAtFixedRate}} should be used as the argument to {{remove}}. 

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