topic Re: close_wait connections going up on Tomcat in Open Q&A

close_wait connections going up on Tomcat

hans_hofkens — Mon, 29 Apr 2019 20:36:15 GMT

We have a few servers where we see close_wait connections piling up until we reached the limit. As I understood that the application should close the close_wait sockets I suspect this to be an application issues. I can't find anything in the code execution indicating that nor do I something suspicious in Dynatrace that would warn us.

Re: close_wait connections going up on Tomcat

ChadTurner — Fri, 24 Jul 2020 14:46:38 GMT

you could put in a custom detection for that string of close_warn and Dynatrace will alert you. This method can also be done at a log standpoint as well.

Re: close_wait connections going up on Tomcat

ChadTurner — Fri, 24 Jul 2020 14:48:45 GMT

https://www.dynatrace.com/support/help/how-to-use-dynatrace/problem-detection-and-analysis/basic-concepts/event-types/custom-alerts/

Re: close_wait connections going up on Tomcat

Joe_Hoffman — Fri, 24 Jul 2020 15:13:01 GMT

Close_wait()'s can pile up when a TCP connection gets closed from the other end and leaves your end dangling. So perhaps it would be helpful to track the call tree of the close wait threads AND track the remote endpoint. This might give you visibility into a pattern of loosing connections to a common remote endpoint which is really the root cause.