All, I'm doing some scalability testing of an app in Tomcat 7.0.73.
Some relevant connector config details: maxThreads=80 maxKeepAliveRequests=100 keepAliveTimeout=10000 maxConnections unspecified (defaults to maxThreads according to the docs) acceptCount unspecified (100 according to the docs) clientAuth=true FWIW, I'm testing two Tomcat instances on the same server. They are behind a load balancer. It appears that when the load generator tries to exceed maxThreads, the new connection rate goes up quickly and CPU usage shoots up with it. I assume this is because Tomcat is proactively closing idle keep alive connections to service new connections. In an effort to keep the CPU in check, I tried increasing maxThreads from 80 to 120. This seemed to work well in a lot of ways. New connection rate didn't increase as much, CPU didn't increase as much, there was more connection reuse (more requests per connection,) and response times didn't deteriorate as much. Great, right? Then I noticed a large increase in "Connection refused" errors on the load generator. In other words, a higher maxThreads also results in a high error rate. The total hits per second from the client's perspective is about 60 in both cases. With maxThreads=80, there are about 3 connection refused errors per second at that volume. With maxThreads=120, there are about 10 connection refused errors per second. I have no idea why this is. Can someone explain this or what I can do about it? Thanks John
