08-Nov-2020 16:58:08.639 WARNING [ContainerBackgroundProcessor[StandardEngine[Catalina]] org.apache.catalina.valves.StuckThreadDetectionValve.notifyStuckThreadCompleted Thread [http-nio-8080-exec-72] (id=) was previously reported to be stuck but has completed. It was active for approximately [431,473] milliseconds. There is/are still  thread(s) that are monitored by this Valve and may be stuck.
08-Nov-2020 16:58:08.641 WARNING [ContainerBackgroundProcessor[StandardEngine[Catalina]]] org.apache.catalina.valves.StuckThreadDetectionValve.notifyStuckThreadCompleted Thread [http-nio-8080-exec-12] (id=) was previously reported to be stuck but has completed. It was active for approximately [512,214] milliseconds.
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This error message is sometimes accompanied by performance issues and/or crashes of a Confluence instance. There is, indeed, a root cause to be found - but this is hard just from having this warning message at hand.
Do you see lags or crashes of your Confluence instance? Is this also applying to Jira (as you tagged Jira here)? Do you have both of them running on one server?
Did you upgrade recently to a newer version?
Did you change Apps recently (upgrade/install)?
Although not knowing the specific setup it could also be a shortage of available memory.
Please also review this useful article:
With some more information somebody here might be able to help you further.
Hi Community! We're thrilled to share that Team Calendars for Confluence is now a built-in feature for Confluence Data Center releases 7.11 and beyond. A long time favorite, Team Cale...
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