title: Apache + Tomcat with mod_jk - Web site hangs
body: <p>I have a website with apache 1.3(SSL enabled) + mod_jk + tomcat 5.5 on Linux redhad setup.  Just recently i started having a downtime problem with my web site. Once a day, i get my web site hang on port 80. But if i access directly through 8080 tomcat responses and web site works fine. Both 80 and 8080 ports are accessible but apache and tomcat connection with mod_jk is broken. Only after i restart tomcat, the things get back to normal. </p>
  
  <p>I just configured apache mod_Jk to log the errors, so i will see if there will be any error on the next hang. </p>
  
  <p>apache mod_js conf:</p>
  
  <pre><code>JkShmSize   1000M
  </code></pre>
  
  <p>apache workers conf:</p>
  
  <pre><code>worker.list=worker1
  worker.worker1.type=ajp13
  worker.worker1.host=127.0.0.1
  worker.worker1.port=8009
  worker.worker1.lbfactor=1
  worker.worker1.socket_keepalive=1
  worker.worker1.recycle_timeout=180
  worker.worker1.sticky_session=False
  </code></pre>
  
  <p>I checked web application error/warn logs on tomcat, i have some "out of memory" java exceptions. Can application errors cause this issue ? Can it be website overload problem or memory leak ? Currently <code>dev/mapper/VolGroup00-LogVol00</code> has only 4% free space. Can it be a cause for the problem ?</p>
  
  <p>I also got this log entry, it matchs the server hang time:</p>
  
  <blockquote>
    <p>/var/log/messages: possible SYN flooding on port 8009. Sending cookies</p>
  </blockquote>
  
  <p><strong>Update:</strong>
  I just got another down, the mod_jk log gives this:</p>
  
  <p><code>
  [Sun Nov 14 00:57:03 2010] [error] ajp_connection_tcp_get_message::jk_ajp_common.c (961): Can't receive the response message from tomcat, network problems or tomcat is$
  [Sun Nov 14 00:57:03 2010] [error] ajp_get_reply::jk_ajp_common.c (1503): Tomcat is down or refused connection. No response has been sent to the client (yet)
  [Sun Nov 14 00:57:08 2010] [error] ajp_connection_tcp_get_message::jk_ajp_common.c (961): Can't receive the response message from tomcat, network problems or tomcat is$
  [Sun Nov 14 00:57:08 2010] [error] ajp_get_reply::jk_ajp_common.c (1503): Tomcat is down or refused connection. No response has been sent to the client (yet)
  [Sun Nov 14 00:57:12 2010] [error] ajp_connection_tcp_get_message::jk_ajp_common.c (961): Can't receive the response message from tomcat, network problems or tomcat is$
  [Sun Nov 14 00:57:12 2010] [error] ajp_get_reply::jk_ajp_common.c (1503): Tomcat is down or refused connection. No response has been sent to the client (yet)
  [Sun Nov 14 00:57:12 2010] [error] ajp_service::jk_ajp_common.c (1758): Error connecting to tomcat. Tomcat is probably not started or is listening on the wrong port. w$
  [Sun Nov 14 00:57:12 2010] worker1 mydomain.com 50.999342
  </code></p>
  
  <p>Looks my website is down on 8009 port. AJP 1.3 connector serves apache mod_jk on 8009 port.</p>
  
  <p>Any help or advice would be highly appreciated.</p>
  
  <p>Thanks.</p>