Flight Engineer
Flight Engineer

503 (service unavailable) and not able to access the application

Hi All,


actually one issue faced due to 500 errors in Application JVM log . 

example box name is = x.x.x.x (A Box),


in A Box running with  both tomcat and httpdX services .


tomcat JVM log showing 500 error but after restart HTTPDX issue resolved.


Application (tomcat)JVM not restart but without issues working good (here tomcat JVM running with old time stamp) and only restarted HttpdX.


actually in HttpdX error.log contain below information:


[Time-Stamp] [proxy:error] [pid 123: tid 456] (111) connection refused: AH00957:ajb:attempt to connect X.X.X.X ( A Box IP address/local host ) failed.



[Time-Stamp] [proxy:error] [pid 123:tid 456] AH00959:X_proxy_connect_backed disabling worker for X.X.X.X (A Box IP address/local host) for 60s.



[Time-Sramp] [proxy:error] [pid 123:tid 456] AH00940:apj:disabled for X.X.X.X ( A Box IP address/local host) .


 Currently I don't the logs .


box details :

Operating System: Linux 6.x,

HTTPD :2.4.6,

tomcat :8,

DB : oracle 11g.



could you please let me provide solution for fix without restart HttpdX. 
I hope explained issue clearly. 
if possible, kindly share the cause of the issue.


regards ,




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2 Replies

We would need much more detailed information to be able to help you, for example the complete names and version names for your software. There is no such thing as "Linux 6.x" I assume you mean RHEL 6.x but what is "x"? And what about "httpdX" what it means?

The log messages seem to indicate that you httpd instance is running a mod_jk connector, but it could be running other modules that provide AJP connectivity to Tomcat. There are many network settings from both httpd and tomcat that need to match, else you would see these errors.

Someone would need details about your server and network topolity and see the http and tomcat configuration files to suggest potential fixes. These fixes would probably require retarting httpd.

It could also be that a firewall is blocking traffic between your httpd and tomcat instances. Even if they are on the same server, they are still subject to kernel firewall rules and SELinux.

If you have a RHEL subscription, you could open a support request. That would the easiest path.

0 Kudos

As per the problem description and the logs of Httpd, it is evident that connection pool worker to the backend server is in the error state and by default, Httpd will not forward any requests to that server until the timeout expires (default is 60 seconds).

You can try to set the following, to avoid this situation, in Proxy Pass.

ProxyPass / http://<IP>:<Port> retry=0

In your case, error 500 and could be due to some other reasons and hence you need to check access log on both Httpd and Apache Tomcat to map the response code for the same request.

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