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https://issues.apache.org/jira/browse/WICKET-7002?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17600411#comment-17600411
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ASF GitHub Bot commented on WICKET-7002:
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dashorst merged PR #535:
URL: https://github.com/apache/wicket/pull/535




> Application metadata access should not require synchronization
> --------------------------------------------------------------
>
>                 Key: WICKET-7002
>                 URL: https://issues.apache.org/jira/browse/WICKET-7002
>             Project: Wicket
>          Issue Type: Improvement
>          Components: wicket-core
>    Affects Versions: 8.14.0, 9.11.0
>            Reporter: Martijn Dashorst
>            Priority: Minor
>         Attachments: Screenshot 2022-09-02 at 17.18.44.png
>
>
> The methods getMetaData and setMetaData from Application have synchronized 
> modifiers applied to them such that they block on the application instance.
> This can cause blocking issues. When I looked at the monitor usage in our 
> application running in production the Application metadata locks are 
> responsible for 57% of all monitor usage.
> I've included a screenshot of the monitor usage reverse call stacks.
> The implementation should be changed to a ConcurrentHashMap so we can remove 
> the synchronization from the getter and setter, and just use the hashmap's 
> O(1) lookup rather than MetaDataKey's O( 1) lookup. This will eliminate the 
> blocking and (possibly) long lookups of metadata in the Application instance.
> Note this does not involve modifying the component, session or requestcycle 
> metadata implementations (yet).
> IMO this should be backported to at least 9, as this is a semver compatible 
> change.



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