Apache closes AJP/1.3 connections but for some reason, these connection close requests do not close Tomcat connections. As a result, at Apache end, we have 0 AJP connections but at the Tomcat side, we have to many established AJP connections emanating from the Apache. This is "half-closed TCP connection" problem. This issue is mostly faced when there are wrongly configured Firewall rules.
To resolve this issue please follow steps:
1. Edit $TOMCAT_HOME/conf/server.xml and search for below line:
<Connector port="8009" protocol="AJP/1.3" redirectPort="8443"/>
2. Add ConnectionTimout Connector attribute to the above line.
eg. <Connector port="8009" protocol="AJP/1.3" redirectPort="8443" connectionTimeout="300000"/>
3.Save and exit the file
4. Restart Tomcat service