On 02.03.2009 20:28, Mohit Anchlia wrote:
I will change the JkLogLevel and post the results. I have a question
though: Does prepost_timeout also detect if it received http code such
as 503 from app server.
prepost_timeout activates Cping/Cpong before each request. mod_jk will
send a tiny test packet to the ap server before each request, and the
AJP protocol stack of the app server will immediately respond with a
tiny reply packet, indicating that it is still alive and able to parse
AJP messages. The web application itself is not involved in this part of
the processing, neither is any http request or response (or their AJP
equivalent).
So prepose_timeout will detect, if it receives some garbage (anything
different from a Cpong packet), but http responses with http status
codes are only generated much later and will thus not influence the
prepose Cping/Cpong result.
See also:
http://tomcat.apache.org/connectors-doc/generic_howto/timeouts.html
Regards,
Rainer
On Wed, Feb 25, 2009 at 9:05 AM, Rainer Jung<rainer.j...@kippdata.de> wrote:
On 25.02.2009 17:10, Mohit Anchlia wrote:
you are right there is a mod-jk.conf. So given my workers.properties
file what should I change so that mod_jk detects that app server is
down before attempting to send the request. Shouldn't "retries" in
workers.properties try to connect to some other app server instead.
Just a wild guess: your prepost timeout of 5 milliseconds produces the error
messages you cited. First correct this timeout, then do another clean test
on your test system. You can even increase JkLogLevel to trace (not in
production) so we can see exactly what is going on. Do not send many
requests with JkLogLevel trace, just do a minimal test that shows the
problem.
The early detection of a broken instance should be possible with your
configuration.
Here is mod-jk.conf
# Where to find workers.properties
JkWorkersFile conf/workers.properties
# Where to put jk logs
JkLogFile /var/log/apache2/mod_jk.log
# Set the jk log level [debug/error/info]
JkLogLevel error
# Allow mod_jk worker status reports, with the URL of
http://servername/JkStatus
## This is very helpful for monitoring purposes, but should be
## allowed from the local machine.
<Location /JkStatus>
Order deny,allow
Deny from all
Allow from localhost
</Location>
#JkMount /JkStatus status
# Below line forward all requests to application server
#JkMount /* local
On Wed, Feb 25, 2009 at 2:55 AM, Rainer Jung<rainer.j...@kippdata.de>
wrote:
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
workers.properties. 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 workers.properties 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<rainer.j...@kippdata.de>
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
(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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