Connections to webapps failed with ajp protocol (ProcessEngineFilter does not seem to be working ?)

I’m running camunda on tomcat; when connecting to camunda from apache2.4’s reverse proxy, the mod_proxy_http connection works fine, but the mod_proxy_ajp connection has failed.

An excerpt from httpd.conf

<Location /camunda>
   ProxyPass ajp://camunda-demo:8009/camunda/

Excerpt from server.xml

<Connector protocol="AJP/1.3" address="" secretRequired="false" tomcatAuthentication="false" port="8009" redirectPort="8443"/>

Is there any other place to configure?