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From Rainer Jung <>
Subject Re: mod_jk not working as expected - is there a bug??
Date Wed, 25 Feb 2009 10:55:53 GMT
On 25.02.2009 02:47, Mohit Anchlia wrote:
> In httpd conf I just see JkMount and no other directive. I searched for Jk.

There should be others as well, for instance JkWorkersFile to point to 
your The names of the directives are case 
insensitive, they can also be in files included to your main httpd 
configuration file via include directives.

> Here is file:
> # appfe1
> worker.appfe1.socket_timeout=5

I generally don't like socket_timeout. Others do :)

> worker.appfe1.prepost_timeout=5

5 milliseconds prepost timeout? You're kidding. I assume it should have 
been 5000.

> worker.appfe1.recycle_timeout=900

This is deprecated. Use connection_pool_timeout instead. The value is 
OK, you should set connectionTimeout on the Tomcat AJP connector to 
900000 then.

Since you are using prefork MPM, you might want to set 
connection_pool_minsize to 0 if you want to keep the number of 
established connections low.

And the same for the other members of the load balancer.

> On Tue, Feb 24, 2009 at 4:50 PM, Rainer Jung<>  wrote:
>> On 25.02.2009 00:00, Mohit Anchlia wrote:
>>> Reposting:
>>> Apache Server - 2.2
>>> Tomcat server 6
>>> Jboss - 4.2
>>> We have Web Servers talking to Jboss App Servers over mod_jk. When we
>>> do our patch or upgrade of software we do it in rolling fashion so
>>> that there is "0" customer impact. But it looks like mod_jk load
>>> balancer on Web server doesn't detect it as soon as Jboss App Server
>>> goes down. Our goal is to have 0 customer impact. So my question is
>>> what can we do to overcome this problem. Web Server sees Http Error
>>> Code 503.
>>> Information from log file:
>>> [Mon Feb 23 13:39:42.146 2009] [31682:4143745888] [error]
>>> ajp_connection_tcp_get_message::jk_ajp_common.c (966): (appfe4) can't
>>> receive the response message from tomcat, network problems or tomcat
>>> ( is down (errno=104)
>>> [Mon Feb 23 13:39:42.147 2009] [31682:4143745888] [error]
>>> ajp_service::jk_ajp_common.c (2097): (appfe4) Connecting to tomcat
>>> failed. Tomcat is probably not started or is listening on the wrong
>>> port
>> This means that mod_jk detected that your backend is down and thus puts it
>> into an error state. All following requests will no longer be sent to this
>> backend. Once a minute it will send a request there and try, but as long as
>> it is down this test will not succeed and thus all requests will be sent to
>> other nodes.
>> The first request that gets sent to the backend you stopped might get an
>> error back. If you want to prevent that from happening, use Cping/Cpong:
>> so we will detect the broken node before actually sending a request there.
>> More details are not possible to give without your JK configuration (Jk
>> directive sin httpd configuration files, and if used
>> The line number of the above message tells me you are using mod_jk 1.2.25.
>> Although there's nothing wrong in principal with 1.2.25, we always try to
>> improve and you might consider switching to 1.2.27.
>> You should also increase your JkLogLevel to info. As long as only occasional
>> info messages are in your log file everything is fine, but once error
>> messages show up, the additional info messages contain useful formation.
>> Regards,
>> Rainer

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