I used jenkins and apache httpd and mod_jk 1.2.32.
Jenkins throws NullPointerException.

mod_jk config:

• mod_jk.conf

  JkWorkersFile conf/workers.properties
  JkMount /* jenkins

• workers.properties

  worker.list=jenkins
  worker.jenkins.type=ajp13
  worker.jenkins.host=localhost
  worker.jenkins.port=8009

jenkins:

• log

  :
  Feb 29, 2012 1:11:07 PM hudson.WebAppMain$2 run
  INFO: Jenkins is fully up and running
  Feb 29, 2012 1:26:40 PM winstone.Logger logInternal
  SEVERE: Error within request handler thread
  java.lang.NullPointerException
  at java.util.Hashtable.put(Hashtable.java:411)
  at winstone.ajp13.Ajp13IncomingPacket.parsePacket(Ajp13IncomingPacket.java:163)
  at winstone.ajp13.Ajp13Listener.allocateRequestResponse(Ajp13Listener.java:184)
  at winstone.RequestHandlerThread.run(RequestHandlerThread.java:79)
  at java.lang.Thread.run(Thread.java:636)
  :

mod_jk 1.2.32 sending null AJP request attribute value to server.

workaround: configure LB worker to mod_jk.

• workers.properties

  worker.list=jenkins

  worker.jenkins.type=lb
  worker.jenkins.balance_workers=jenkins1

  worker.jenkins1.type=ajp13
  worker.jenkins1.host=localhost
  worker.jenkins1.port=8009

  or use mod_jk 1.2.31.