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
(10.10.81.89:8009) 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:
http://tomcat.apache.org/connectors-doc/generic_howto/timeouts.html
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,
workers.properties and if used uriworkermap.properties).
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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