10 connection limit with IIS and JK/ISAPI 1.2.14

[David <Da...@bvu.edu>]

I'm using Tomcat 5.5.9 on Windows Server 2003, JDK 1.5.0_04, IIS 6.0, with the JK 1.2.14 isapi_redirector.dll.
 
I've been trying to track down a problem whereby all of the web apps under our Tomcat instance are seeming to stall. There's no indication of any problems in the Tomcat logs themselves. I suspect IIS is unable to forward requests to Tomcat. I either have to recycle the IIS worker process or restart Tomcat to resolve the problem.
 
Here's what I'm seeing with netstat (port 8008 is my AJP 1.3 port):
 
Z:\>netstat -a -n | grep 8008
  TCP    0.0.0.0:8008           0.0.0.0:0              LISTENING
  TCP    147.92.2.137:2871      147.92.2.137:8008      ESTABLISHED
  TCP    147.92.2.137:2915      147.92.2.137:8008      ESTABLISHED
  TCP    147.92.2.137:2944      147.92.2.137:8008      ESTABLISHED
  TCP    147.92.2.137:2965      147.92.2.137:8008      ESTABLISHED
  TCP    147.92.2.137:2969      147.92.2.137:8008      ESTABLISHED
  TCP    147.92.2.137:3019      147.92.2.137:8008      ESTABLISHED
  TCP    147.92.2.137:3034      147.92.2.137:8008      ESTABLISHED
  TCP    147.92.2.137:3039      147.92.2.137:8008      ESTABLISHED
  TCP    147.92.2.137:3041      147.92.2.137:8008      ESTABLISHED
  TCP    147.92.2.137:3060      147.92.2.137:8008      ESTABLISHED
  TCP    147.92.2.137:8008      147.92.2.137:2871      ESTABLISHED
  TCP    147.92.2.137:8008      147.92.2.137:2915      ESTABLISHED
  TCP    147.92.2.137:8008      147.92.2.137:2944      ESTABLISHED
  TCP    147.92.2.137:8008      147.92.2.137:2965      ESTABLISHED
  TCP    147.92.2.137:8008      147.92.2.137:2969      ESTABLISHED
  TCP    147.92.2.137:8008      147.92.2.137:3019      ESTABLISHED
  TCP    147.92.2.137:8008      147.92.2.137:3034      ESTABLISHED
  TCP    147.92.2.137:8008      147.92.2.137:3039      ESTABLISHED
  TCP    147.92.2.137:8008      147.92.2.137:3041      ESTABLISHED
  TCP    147.92.2.137:8008      147.92.2.137:3060      ESTABLISHED
 
Every time the stall has happened, I have noticed that there are always exactly ten connetions between IIS and Tomcat (they're on the same server). Everything works fine until we reach this point.
 
In my JK log, I'm seeing things like this:
 
[Wed Aug 24 14:10:57 2005] [error] ajp_connection_tcp_get_message::jk_ajp_common.c (961): Can't receive the response message from tomcat, network problems or tomcat is down (147.92.2.137:8008), err=-54
[Wed Aug 24 14:10:57 2005] [error] ajp_get_reply::jk_ajp_common.c (1503): Tomcat is down or refused connection. No response has been sent to the client (yet)
 
 
My workers.properties looks like this:
 
worker.list=ajp13a
 
worker.ajp13a.port=8008
worker.ajp13a.host=www.bvu.edu
worker.ajp13a.type=ajp13
 
cachesize=20
cache_timeout=600
recycle_timeout=300
 
 
And here's the AJP connection defininition from my server.xml:
 
    <Connector port="8008"
               maxThreads="150" minSpareThreads="25" maxSpareThreads="75"
               enableLookups="false" redirectPort="443" debug="5" connectionTimeout="20000"
               protocol="AJP/1.3"/>
 
 
Any idea what might be happening? It sure looks like I'm hitting some kind of 10 connection limit somewhere, but I can't seem to figure out where.