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From "Colin Patrick McCabe (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-4824) FileInputStreamCache.close leaves dangling reference to FileInputStreamCache.cacheCleaner
Date Wed, 15 May 2013 19:31:16 GMT

    [ 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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