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https://issues.apache.org/jira/browse/WICKET-6793?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17125704#comment-17125704
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Martin Tzvetanov Grigorov commented on WICKET-6793:
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Actually it looks like two separate problems.
> OOM in AsynchronousPageStore
> ----------------------------
>
> Key: WICKET-6793
> URL: https://issues.apache.org/jira/browse/WICKET-6793
> Project: Wicket
> Issue Type: Bug
> Components: wicket-core
> Affects Versions: 8.7.0
> Reporter: Vladimir Kubinda
> Assignee: Sven Meier
> Priority: Major
> Fix For: 9.0.0-M6, 8.9.0
>
>
> After migrating to version 8.X, we face an out-of-memory issue. To clear the
> locked memory, the server must be restarted several times a week.
> After analyzing the heap dumps, we found that the vast majority of the heap
> is AsynchronousPageStore.entryMap. We started looking for some solutions and
> found a WICKET-6629 error. I think this fix is not enough and should
> include removing AsynchronousPageStore.Entry also from
> AsynchronousPageStore.entryMap not only from AsynchronousPageStore.entries.
> Let me explain what I think. If StoreSettings.isAsynchronous is set to true
> (default option), Wicket uses AsynchronousPageStore to store the pages.
> AsynchronousPageStore.storePage method inserts the entry to entryMap on line
> 278 (version 8.7.0). If the entries are not full, entry is inserts to entries
> queue on line 282.
> Then wait until the PageSavingRunnable poll entry from queue, store it and
> remove it from entryMap on line 209. Now everything is fine.
> But what if the entry's session is unbind (expires, logout etc.), and entry
> was already inserted into entries and entryMap? Therefore, there is an
> AsynchronousPageStore.unbind method that removes all entries for the session
> from entries queue. But entry that has not yet been saved (in
> PageSavingRunnable, because it was waiting in queue) still exists and will
> not be removed from entryMap.
> When the entry is inserted into the AsynchronousPageStore.entryMap and
> AsynchronousPageStore.entries queue, there is only one place where the entry
> can be deleted from the AsynchronousPageStore.entryMap, and that is on line
> 209 in PageSavingRunnable.run method. But when we deleted an entry from the
> AsynchronousPageStore.entries, the entry in the
> AsynchronousPageStore.entryMap remains there, because if statment on line 205
> in PageSavingRunnable.run.
> So now if you have thousands of users and the sites are huge, it's only a
> matter of time before it starts to cause a problem.
> I think solution is remove all entries from unbinded session from
> AsynchronousPageStore.entryMap.
> I hope that I'm right.
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