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https://issues.apache.org/jira/browse/COCOON-2109?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12519003
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Jörg Heinicke commented on COCOON-2109:
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Are you sure that modifying the value of the sort criteria does not change the
order of the elements? At the end it's the question when the elements are
sorted - on inserting them or on iterating over them. I'm pretty sure it's the
latter and then there would be no problem. The Javadoc for SortedSet says: "A
set that further guarantees that its iterator will traverse the set in
ascending element order".
A potential problem I can see is the modification of the lastAccessTime WHILE
actually iterating over the set. The iterating itself is for sure synchronized
to avoid ConcurrentModificationExceptions or something like this. But at that
time you still can change the lastAccessTime. As soon as the
ContinuationsManagerImpl gets to the first continuation with a modified
lastAccessTime it would stop iterating and the expired continuations with a
later lastAccessTime than the updated one had before would survive the cleanup.
Does it make sense? (I did not look into the code.)
> Incorrent cleanup of expired continuations
> ------------------------------------------
>
> Key: COCOON-2109
> URL: https://issues.apache.org/jira/browse/COCOON-2109
> Project: Cocoon
> Issue Type: Bug
> Components: - Flowscript
> Affects Versions: 2.1.6, 2.1.7, 2.1.8, 2.1.9, 2.1.10, 2.1.11-dev (Current
> SVN)
> Reporter: Miguel Cuervo
> Attachments: ContinuationsManagerImpl.java.patch
>
>
> The class ContinuationsManagerImpl is in charge of cleaning up expired
> continuations. It does so in the method expireContinuations. In this method
> there is a loop using an iterator over a SortedSet of continuations
> (WebContinuation). The loop is expecting that the continuations are ordered
> from oldest to newest. The loop stops in the first continuation that is not
> expired. The logic is correct since all the newer continuations could not be
> expired.
> However, the problem comes from the ordering of the continuations. To have
> the continuations ordered by lastAccessTime the program uses a TreeSet as a
> container of the continuations. The continuations implement the compareTo
> interface using the lastAccessTime and when a continuation is inserted in the
> container, it gets correctly ordered. But after the insertion, the
> continuation can change its lastAccessTime using the method
> WebContinuation.updateLastAccessTime() called from
> WebContinuation.getContinuation(). The ordering of the TreeSet is not updated
> with the change and when the program iterates over it, it does not get the
> continuations in the order expected.
> The result of this bug is that under hevy load many expired continuations may
> be around before the loop actually clean them up, eating memory resources and
> causing OutOfMemory.
> To fix it, a patch is provided that uses a HashSet for the continuations
> container and loops over all the continuations to check if they have expired.
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