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https://issues.apache.org/jira/browse/WICKET-7002?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17600412#comment-17600412
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ASF subversion and git services commented on WICKET-7002:
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Commit dcd3b3e0c985280c682a526ace2e591f2af25287 in wicket's branch
refs/heads/wicket-9.x from Martijn Dashorst
[ https://gitbox.apache.org/repos/asf?p=wicket.git;h=dcd3b3e0c9 ]
WICKET-7002 Remove blocking code from Application#get/setMetaData
By replacing the datastructure for Application class's metaData field
with a ConcurrentHashMap we can remove the synchronization on the
application instance and speed up lookups of the metadata. For at least
one application this will remove 50% of all blocking calls.
(cherry picked from commit 8c770c4337cc2649385aea49f02d29a357ac7acf)
> 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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