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Active Threads in Tomcat - what is this telling me ?

Question asked by dave.richards on Mar 16, 2016
Latest reply on Mar 17, 2016 by Florian_Cheval

Hi - in our location we are gradually moving into Tomcat/JBOSS application servers and away from Websphere. In the past we used the websphere agent with PMI enabled and monitored the web container thread pool size as a key alert metric.


In Tomcat, as we don't have PMI, we are looking at the "Threads|Active Threads" metrics. What we are seeing is that the value just grows and grows, it doesn't appear to reset until a server restart. So as a monitoring metric we aren't getting any value from it.


Any ideas/theories about why this metric value just grows upwards ? We think it may be that the thread objects are left on the heap and not gc'd, and the agent is returing that number as the "Active Threads" value.


We have tried to do a thread dump via the Investigator option but this is not allowed as the thread dump total stack trace exceeds 12,000 - is that a configurable value so we could increase it to get a thread dump in this way ?