Tomcat: Does maxActive limit the size of threadpool?

Question

I am having difficulty understanding some of the documentation for the tomcat JDBC thread pool and I was hoping somebody could clarify.

If I have maxActive set to 100, does this mean that the size of the pool is limited to 100, so 50 idle + 50 active for example? Or can I have 100 active connections and 100 idle connections if I so wished, meaning the size could be 200 with maxActive set to 100?

The reason I ask is we have an app with maxActive set to 100 and it stopped handling connections when size reached 100.

Some debug output from when it died :

Initial Size : 100
Active Connection : 28
Idle Connection : 0
Size : 100

Max Active Connections : 100
Max Age : 0
Max Idle : 100
Min Idle : 80
Max Wait : 5000

Log Abandoned : true
Remove Abandoned : true
Remove Abandoned Timeout : 300

timeBetweenEvictionRunsMillis : 60000
minEvictableIdleTimeMillis : 3600000

Validation Query : SELECT 1

Answer 1

If I have maxActive set to 100, does this mean that the size of the pool is limited to 100, so 50 idle + 50 active for example?

That's my understanding of how it works.

Or can I have 100 active connections and 100 idle connections if I so wished, meaning the size could be 200 with maxActive set to 100?

No, maxActive should limit the size of the pool not just "active" connections.

The reason I ask is we have an app with maxActive set to 100 and it stopped handling connections when size reached 100.

This sounds like the expected behavior. Are you expecting to hit the limit, in other words do you legitimately have 100 connections in use?

As a side note, usually the pool will output some helpful logging when you hit a situation like this. You'll see a "PoolExhaustedException" with some additional information. Do you happen to have those log records?

Lastly, have you tried a more recent version of the pool? Can you try the pool that ships with the latest download of Tomcat 7.

http://search.maven.org/#artifactdetails|org.apache.tomcat|tomcat-jdbc|7.0.42|jar

Comments

Thanks for the clarification. We shouldn't legitimately see 100 connections but we are trying to debug issues with our application that may be leaking connections, we are seeing strange behavior that I will reference in a different post as to not confuse things.

I will also try to get our app running on the latest version of tomcat if you think that will help

Now that we know that maxActive dictates the overall size we can adjust our setting, thanks again!