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From "Craig Condit (JIRA)" <j...@apache.org>
Subject [jira] Created: (AMQ-3162) ActiveMQ checkpoint worker makes unnecessary repeated calls to Journal.getFileMap(), leading to excessive memory usage
Date Tue, 25 Jan 2011 23:05:46 GMT
ActiveMQ checkpoint worker makes unnecessary repeated calls to Journal.getFileMap(), leading
to excessive memory usage
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                 Key: AMQ-3162
                 URL: https://issues.apache.org/jira/browse/AMQ-3162
             Project: ActiveMQ
          Issue Type: Bug
    Affects Versions: 5.4.2
            Reporter: Craig Condit
            Priority: Minor


During its cleanup run (default every 30 seconds), MessageDatabase.checkpointUpdate() attempts
to determine which data files are safe to delete. It calls Journal.getFileMap() repeatedly
within a loop to determine if the file is referenced in memory. Journal.getFileMap() creates
a new TreeMap from the underlying map. Unfortunately, as the number of data files grows on
a busy broker, this can be called hundreds or even thousands of times, leading to excessive
run time, memory churn, and overall poor performance (observed in our environment).

The attached patch simply moves the call to getFileMap() outside the loop so that it runs
in O(gcCandidates.size) vs. O(gcCandidates.size * fileMap.size).

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