Martijn Dashorst created WICKET-7002:
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Summary: 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: 9.11.0, 8.14.0
Reporter: Martijn Dashorst
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(n) 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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