tomcat stops responding when fourth service ajp connector added

Question

A Tomcat 8 server has been serving as a reverse proxy behind apache httpd on CentOS 7. Tomcat has had three services running, each with an ajp connection to apache. But when I add a fourth service with its own fourth ajp connection, apache stops responding altogether. How can I assign a fourth ajp connection? /opt/tomcat/conf/server.xml is: <?xml version='1.0' encoding='utf-8'?> <Server port="8005" shutdown="SHUTDOWN"> <Listener className="org.apache.catalina.startup.VersionLoggerListener" /> <Listener className="org.apache.coyote.ajp.AjpProtocol" SSLEngine="on" /> <Listener className="org.apache.catalina.core.JreMemoryLeakPreventionListener" /> <Listener className="org.apache.catalina.mbeans.GlobalResourcesLifecycleListener" /> <Listener className="org.apache.catalina.core.ThreadLocalLeakPreventionListener" /> <GlobalNamingResources> <Resource name="UserDatabase" auth="Container" type="org.apache.catalina.UserDatabase" description="User database that can be updated and saved" factory="org.apache.catalina.users.MemoryUserDatabaseFactory" pathname="conf/tomcat-users.xml" /> </GlobalNamingResources> <Service name="Catalina"> <Connector port="8080" protocol="HTTP/1.1" connectionTimeout="20000" redirectPort="8443" /> <Connector port="8009" protocol="AJP/1.3" redirectPort="8443" connectionTimeout="10000" keepAliveTimeout="10000" /> <Engine name="Catalina" defaultHost="localhost"> <Realm className="org.apache.catalina.realm.LockOutRealm"> <Realm className="org.apache.catalina.realm.UserDatabaseRealm" resourceName="UserDatabase"/> </Realm> <Host name="localhost" appBase="webapps" unpackWARs="true" autoDeploy="true"> <Valve className="org.apache.catalina.valves.AccessLogValve" directory="logs" prefix="localhost_access_log" suffix=".txt" pattern="%h %l %u %t &quot;%r&quot; %s %b" /> </Host> </Engine> </Service> <Service name="Upload"> <Connector port="8081" protocol="HTTP/1.1" connectionTimeout="20000" redirectPort="8444" /> <Connector port="8010" protocol="AJP/1.3" redirectPort="8444" connectionTimeout="10000" keepAliveTimeout="10000" /> <Engine name="Catalina" defaultHost="localhost"> <Realm className="org.apache.catalina.realm.LockOutRealm"> <Realm className="org.apache.catalina.realm.UserDatabaseRealm" resourceName="UserDatabase"/> </Realm> <Host name="localhost" appBase="webapps_upload" unpackWARs="true" autoDeploy="true"> <Valve className="org.apache.catalina.valves.AccessLogValve" directory="logs" prefix="localhost_access_log" suffix=".txt" pattern="%h %l %u %t &quot;%r&quot; %s %b" /> </Host> </Engine> </Service> <Service name="Public"> <Connector port="8082" protocol="HTTP/1.1" connectionTimeout="20000" redirectPort="8445" /> <Connector port="8011" protocol="AJP/1.3" redirectPort="8445" connectionTimeout="10000" keepAliveTimeout="10000" /> <Engine name="Catalina" defaultHost="localhost"> <Realm className="org.apache.catalina.realm.LockOutRealm"> <Realm className="org.apache.catalina.realm.UserDatabaseRealm" resourceName="UserDatabase"/> </Realm> <Host name="localhost" appBase="webapps_public" unpackWARs="true" autoDeploy="true"> <Valve className="org.apache.catalina.valves.AccessLogValve" directory="logs" prefix="localhost_access_log" suffix=".txt" pattern="%h %l %u %t &quot;%r&quot; %s %b" /> </Host> </Engine> </Service> <Service name="domain3"> <Connector port="8083" protocol="HTTP/1.1" connectionTimeout="20000" redirectPort="8446" /> <Connector port="8012" protocol="AJP/1.3" redirectPort="8446" connectionTimeout="10000" keepAliveTimeout="10000" /> <Engine name="Catalina" defaultHost="localhost"> <Realm className="org.apache.catalina.realm.LockOutRealm"> <Realm className="org.apache.catalina.realm.UserDatabaseRealm" resourceName="UserDatabase"/> </Realm> <Host name="localhost" appBase="webapps_domain3" unpackWARs="true" autoDeploy="true"> <Valve className="org.apache.catalina.valves.AccessLogValve" directory="logs" prefix="localhost_access_log" suffix=".txt" pattern="%h %l %u %t &quot;%r&quot; %s %b" /> </Host> </Engine> </Service> <Service name="domain4"> <Connector port="8084" protocol="HTTP/1.1" connectionTimeout="20000" redirectPort="8447" /> <Connector port="8013" protocol="AJP/1.3" redirectPort="8447" connectionTimeout="10000" keepAliveTimeout="10000" /> <Engine name="Catalina" defaultHost="localhost"> <Realm className="org.apache.catalina.realm.LockOutRealm"> <Realm className="org.apache.catalina.realm.UserDatabaseRealm" resourceName="UserDatabase"/> </Realm> <Host name="localhost" appBase="webapps_domain4" unpackWARs="true" autoDeploy="true"> <Valve className="org.apache.catalina.valves.AccessLogValve" directory="logs" prefix="localhost_access_log" suffix=".txt" pattern="%h %l %u %t &quot;%r&quot; %s %b" /> </Host> </Engine> </Service> </Server> I tried adding the following inside the Public service above instead of adding a fourth service, but I am getting the same error: <!-- The following host is from: https://stackoverflow.com/questions/10704833/tomcat-and-multiple-domains-applications <Host name="domain4.com" appBase="webapps_domain4" unpackWARs="true" autoDeploy="true"> <Valve className="org.apache.catalina.valves.AccessLogValve" directory="logs" prefix="domain4_access_log." suffix=".txt" pattern="%h %l %u %t &quot;%r&quot; %s %b" /> </Host> --> The Apache logs are: [Fri Oct 30 18:14:05.197127 2015] [proxy:error] [pid 25060] (111)Connection refused: AH00957: AJP: attempt to connect to SERVER.ip.addr:8011 (SERVER.ip.addr) fail$ [Fri Oct 30 18:14:05.197220 2015] [proxy:error] [pid 25060] AH00959: ap_proxy_connect_backend disabling worker for (SERVER.ip.addr) for 60s [Fri Oct 30 18:14:05.197238 2015] [proxy_ajp:error] [pid 25060] [client remote.CLIENT.ip:54548] AH00896: failed to make connection to backend: SERVER.ip.addr I read this other posting and this second other posting, but they did not answer my question. Also, the httpd.conf has not changed, so I am omitting it for now to stay on topic as a java tomcat question.