Tomcat 8.5.33 Java WebApp is suddenly going much slower

Question

I have a java web application that is beign developed in Java 8 and that is beign deployed on two tomcat 8.5.33 clustered servers running on a Oracle Linux Server 7.5. The problem, is as follows.

The war has been deployed continuously for the last couple of weeks without any problems, the thing is that suddenly it started working very slowly.

After investigating I came up with some causes and solutions to them, but, none of them seemed to be the cause of my problem.

At first I thought it could have been a memory leak or something like that, but after seeing that that wasn´t the case, rebooting the system just in case and giving tomcat more memory to use, nothing worked. I also found that there was a possibility of the problem being caused by a too large catalina.out file, that also wasn´t the case.

When looking in the logs produced by tomcat it seems like nothing is going wrong besides:

05-Dec-2018 13:51:28.412 SEVERE [main] org.apache.catalina.ha.deploy.FarmWarDeployer.start FarmWarDeployer can only work as host cluster subelement!

This seems to be a cluster error but as I have investigated this shouldn´t be the cause of my problem, besides that logs it is continuously logging:

05-Dec-2018 15:09:16.832 FINE [ContainerBackgroundProcessor[StandardEngine[Catalina]]] org.apache.catalina.session.ManagerBase.processExpires Start expire sessions StandardManager at 1544018956832 sessioncount 1

05-Dec-2018 15:09:16.833 FINE [ContainerBackgroundProcessor[StandardEngine[Catalina]]] org.apache.catalina.session.ManagerBase.processExpires End expire sessions StandardManager processingTime 1 expired sessions: 0

The weird thing is that in my webapp logs you can see where too much time is passing between logs. This occurs randomly every time a servlet is called, doing everything fine until at a random log (random because sometimes it starts at one log, and another time at another one) the logs start being written every 10 seconds.

Log4j2 2.11 is being used for the logs and here is an example of some logs:

05/12/2018 11:53:18 INFO

05/12/2018 11:53:18 INFO

05/12/2018 11:53:18 INFO

05/12/2018 11:53:18 INFO

05/12/2018 11:53:38 INFO

05/12/2018 11:53:48 INFO

05/12/2018 11:53:58 INFO

05/12/2018 11:54:08 INFO

05/12/2018 11:54:18 INFO

05/12/2018 11:54:28 INFO

05/12/2018 11:54:38 INFO

05/12/2018 11:54:48 INFO

05/12/2018 11:54:58 INFO

05/12/2018 11:55:08 INFO

Answer 1

Had the same problem in our system. In our case it was caused by the Linux user that used to launch the Tomcat, it didn't have enough privileges needed for all the Tomcat Apps, so I simply solved it by launching it with the sudo command.

sudo $CATALINA_HOME/bin/startup.sh

I don't have information about why this solved the problem, and what was causing all the slowness, cause of time needs (just wanted to resolve it as quickly as we could). Hope this suits for you.