Re: Apache + 2 tomcat appserver failover configuration (Apache Users)

I've set up a load balancing configuration based on an Apache server
and two tomcats Tomcat6A, and Tomcat6B. I'm trying to set it up so
that Tomcat6B is a failover server, so if Tomcat6A goes down, Tomcat6B
will handle all subsequent requests.

This is a hot standby scenario. IMHO the best is to use mod_jk instead.

Example of mod_jk config for your workers.properties file:

<IfModule jk_module>
   JkWorkersFile   conf/workers.properties
   JkLogFile "|/usr/local/apache2/bin/rotatelogs /usr/local/apache2/logs/mod_jk.log.%Y%m%d 86400"
   JkLogLevel Debug
   JKShmSize 256
   JkShmFile logs/jk.shm
   JkMount /* balance1
   JkMount /jkmanager/* jkstatus
</IfModule>

but from your post I'm not sure if you have mod_jk installed and configured at all.

What you want to achive means that when the balancer worker on Tomcat6A is in error state, the balancer will redirect the sessions to Tomcat6B. This also means though that that user session should exist on Tomcat6B too which on other hand means you need to have some kind of session replication between tomcat servers. I haven't seen your full tomcat config but hope you have cluster set up or the fail over will not work.

I have two questions:
1. Does mod_proxy use the workers.properties file? It doesn't seem to
make any difference what is in workers.properties.
2. How can I set this system up for a failover configuration?

This is killing me. I'm using mod_proxy, mod_proxy_balancer, mod_ajp.

In the load balancer howto, it specifies the configuration I want by
using the workers.properties file, but that file seems to have no
effect on the system behavior. I wonder if it was written before
mod_proxy became a replacement for mod_jk.
_http://tomcat.apache.org/connectors-doc/generic_howto/loadbalancers.html

No matter what I do, if I shut down Tomcat6A, there is no failover
behavior. Existing Tomcat6A request fail (expected) and new requests
fail with 404. Only the existing Tomcat6B request continue.

Header add Set-Cookie "ROUTEID=.%{BALANCER_WORKER_ROUTE}e; path=/"
env=BALANCER_ROUTE_CHANGED
<Proxy balancer://cluster>
BalancerMember ajp://chimps-lb-01.cable.bogus.com:8009 route=Tomcat6A
BalancerMember ajp://chimps-lb-02.cable.bogus.com:8009 route=Tomcat6B
ProxySet stickysession=ROUTEID
</Proxy>

ProxyPass / balancer://cluster/
ProxyPassReverse / balancer://cluster/

For mod_proxy_balancer (if you insist), I would put something like this:

<Proxy balancer://cluster>
BalancerMember ajp://chimps-lb-01.cable.bogus.com:8009 route=Tomcat6A
BalancerMember ajp://chimps-lb-02.cable.bogus.com:8009 route=Tomcat6B status=+H
ProxySet stickysession=ROUTEID nofailover=Off lbmethod=bytraffic
</Proxy>

This puts Tomcat6B worker in hot backup state and the whole traffic is redirected to Tomcat6A. Per my understanding, the above configuration means that when the balancer worker on Tomcat6A is in error state, the balancer will redirect the session to Tomcat6B which is marked as hot backup . The tomcat session replication remark is valid in this scenario too.

The configuration above alternates between each tomcat as request come
in, which is not what I want.

I created a workers.properties file in /etc/httpd/conf/, based on the
loadBalance Howto, but it does not seem to have any effect on the
system. Does mod_proxy use it?

worker.list=balance1

# The load balancer worker balance1 will distribute
# load to the members Tomcat6A, Tomcat6B
worker.balance1.type=lb
worker.balance1.balance_workers=Tomcat6A, Tomcat6B

worker.Tomcat6A.type = ajp13
worker.Tomcat6A.host = chimps-lb-01.cable.bogus.com
worker.Tomcat6A.port = 8009
worker.Tomcat6A.redirect=Tomcat6B
#worker.Tomcat6A.lbfactor = 10

worker.Tomcat6B.type = ajp13
worker.Tomcat6B.host = chimps-lb-02.cable.bogus.com
worker.Tomcat6B.port = 8009
worker.Tomcat6B.activation=disabled

Each tomcat server.xml has
<Engine name="Standalone" defaultHost="localhost" jvmRoute="Tomcat6A">
or
<Engine name="Standalone" defaultHost="localhost" jvmRoute="Tomcat6B">

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