Recently I did not receive a response, after calling a webapp. There was no entry/error in the Application log. It was wired.

Setup: Caller → Apache → Tomcat with Webapp

After inspecting the apache logs, I found the following entries: “AH00992: ajp_read_header: ajp_ilink_receive failed”. I could not reproduce them, they just happened. As it turn out, my image of “my” setup was wrong:

Real Setup: Caller → Apache → Firewall → Tomcat with Webapp

The firewall kept droping the connection. No reason whatsoever. Since I have no controll over the firewall, I modified the timeouts of the http and the application server:

For Apache HTTP + MOD_PROXY: ProxyPass Directive

In Tomcat: Just set the “connectionTimeout” in the AJP connector. Source: JK Timeout Attributes -> Connection Pools and Idle Timeouts