We are running jenkins as a standalone server using a war file. We have enabled AJP13 port so Apache (installed on the same server) can serve it as a proxy. Jenkins runs fine but intermittently throws "Bad AJP13 rcv packet" IOExceptions and stops working. On the browser apache says, system temporarily available. I could connect to jenkins just fine by hitting direct https port it is running.

Here is exception:
============================
INFO: Jenkins is fully up and running
Apr 08, 2014 5:34:58 PM org.eclipse.jetty.util.log.JavaUtilLog warn
WARNING: handle failed?
java.io.IOException: Bad AJP13 rcv packet: 0x5f2e expected 0x1234 org.eclipse.jetty.ajp.Ajp13Parser@17ac5bd
at org.eclipse.jetty.ajp.Ajp13Parser.parseNext(Ajp13Parser.java:276)
at org.eclipse.jetty.ajp.Ajp13Parser.parseAvailable(Ajp13Parser.java:158)
at org.eclipse.jetty.server.BlockingHttpConnection.handle(BlockingHttpConnection.java:72)
at org.eclipse.jetty.server.bio.SocketConnector$ConnectorEndPoint.run(SocketConnector.java:264)
at winstone.BoundedExecutorService$1.run(BoundedExecutorService.java:77)
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:744)
===============================

Apache AJP config:

==========================
ProxyPass /jenkins ajp://localhost:9091/jenkins
ProxyPassReverse /jenkins ajp://localhost:9091/jenkins
ProxyRequests Off
==========================

Any help is appreciated.