Issue
In your controller logs of an HA (active/active) cluster, you see the following error message:
EventQueue overloaded! Failed to process event packet sent from:
Resolution
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To troubleshoot this when running CloudBees CI version 2.452.3.2or newer:- 
Collect a support bundle with the About Jenkins,Information from other replicas, andHazelcast collection summaryoptions.
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The support bundle will contain information about the Hazelcast collections in the file hazelcast-collections.txt.
 
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To troubleshoot this when running CloudBees CI versions older than 2.452.3.2:- 
Add a FINER level logger for com.cloudbees.jenkins.plugins.replication.syncby following Configure Loggers for Jenkins and CloudBees CI. This will provide more information about the events being processed.FINER c.c.j.p.r.s.MessageProvider$ListenerImpl#isActuallyModified: checksum of ... changed so considering save event
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Run collectPerformanceData.shto get consecutive thread dumps when the error is happening, by following Required Data: CloudBees CI hang or high CPU on Kubernetes or Linux.
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Collect a support bundle with the About Jenkins,Information from other replicas, andController Custom Log Recordersoptions.
 
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Submit the above data to CloudBees Support for further analysis at https://support.cloudbees.com.