mod_cluster : Need details on CreateBalancers directive

[jjapache]

Hello,

I have read the documentation about the 'CreateBalancers' directive but I can't figure out what the difference is between option 0 et 2.

Even with multiple VHosts on my server, all balancers are create on all VHosts with both options.

Here is my configuration:

---------------------------------

LoadModule proxy_module modules/mod_proxy.so

LoadModule proxy_ajp_module modules/mod_proxy_ajp.so

LoadModule cluster_slotmem_module modules/mod_cluster_slotmem.so

LoadModule manager_module modules/mod_manager.so

LoadModule proxy_cluster_module modules/mod_proxy_cluster.so

LoadModule advertise_module modules/mod_advertise.so

MemManagerFile /var/tests/p3_cluster/apache_2.4/run/

<IfModule manager_module>

CustomLog "|/soft/apache2.4/bin/rotatelogs /var/tests/p3_cluster/cluster_access_%Y%m%d.log 86400" combined

ErrorLog "|/soft/apache2.4/bin/rotatelogs /var/tests/p3_cluster/cluster_error_%Y%m%d.log 86400"

# CreateBalancers 0

CreateBalancers 2

#ProxyPass / balancer://loadbalancer/

#ProxyPass /jboss balancer://mybalancer/jboss

#ProxyPassMatch ^(/SoucheJBossEdfTest/souche.html)$ !

        Listen 10.11.12.13:8009

        <VirtualHost 10.11.12.13:8009>

                ServerName jj.test.com

                <Directory />

                        Require all granted

                </Directory>

                ServerAdvertise off

                EnableMCPMReceive on

                MaxKeepAliveRequests 0

                KeepAliveTimeout 60

                <Location /mod_cluster-manager>

                        SetHandler mod_cluster-manager

                        Require all granted

                </Location>

        </VirtualHost>

</IfModule>

---------------------------------

Thank you for your explanation.

PS: I am using mod_cluster-1.3.0.Final

[jfclere]

How are you testing that? You are probably always hinting the main server (how is it defined by the way?).

[jjapache]

Maybe I don't understand what you qualify by 'main server'. Your talking about JBoss or Apache ?

Actually I have 4 VHosts on port 80, 81, 443 and 444, and I can hit my JBoss cluster through any of them even if I have 'CreateBalancers 2'.

[jfclere]

I am taking of VirtualHost in httpd.conf the main server is always there it is any configuration which isn't between <VirtualHost...> and </VirtualHost.>

If you are taking about the virtual-host in the application sever you need  UseAlias 1 in httpd.conf that is the Host: hostname that is used for the routing in that case.

[jjapache]

Well, I really don't understand how it works.

In httpd.conf, I have:

ServerName main.test.com

Listen 10.11.12.13:80

Listen 10.11.12.13:81

Then <VirtualHost  10.11.12.13:80> with : ServerName vh1.test.com

And <VirtualHost  10.11.12.13:81> with : ServerName vh2.test.com

If I use CreateBalancers 0 or 2, I can reach my JBoss cluster on both vhosts vh1 and vh2

If I add UseAlias 1 and CreateBalancers 0 or 2 I get HTTP 404 error on both vhosts vh1 and vh2

So, I don't know how to test the difference between CreateBalancers 0 or 2.

[jfclere]

With the configuration you have 0 or 2 will behave the same (I am a bit guessing your configuration). You need to add something in the VirtualHost to see the difference... Like adding a header to using mod_rewrite or even a different access_log.

If you get 404 with UseAlias 1 it is because the <alias name="... /> are not correct in the virtual-server you are using. You need alias name="vh1.test.com" or alias name="vh1" and same for vh2 in the other virtual-server.

[jjapache]

Well, it's OK now for the 404 error.

I have this on JBoss:

<virtual-server name="default-host" enable-welcome-root="false">

  <alias name="vh1.test.com"/>

</virtual-server>

On Apache side I have this :

- httpd.conf

Include /app/tests/p3_cluster/apache2.4/conf/vh1.conf

Include /app/tests/p3_cluster/apache2.4/conf/vh2.conf

Include /app/tests/p3_cluster/apache2.4/conf/mod_cluster.conf

ServerAdmin [e-mail]

ServerName main.test.com

Listen 10.11.12.13:81

Listen 10.11.12.13:80

- vh1.conf

<VirtualHost  10.11.12.13:80>

        LoadModule cache_module modules/mod_cache.so

        DocumentRoot /app/tests/p3_cluster/apache_2.4/htdocs/vh1/

        ServerName vh1.test.com

        ServerAdmin [e-mail]

        CustomLog "|/soft/apache/2.4/bin/rotatelogs /var/tests/p3_cluster/apache_2.4/log/vh1_access_%Y%m%d.log 86400" combined

        ErrorLog "|/soft/apache/2.4/bin/rotatelogs /var/tests/p3_cluster/apache_2.4/log/vh1_error_%Y%m%d.log 86400"

</VirtualHost>

- vh2.conf

<VirtualHost  10.11.12.13:81>

        DocumentRoot /app/tests/p3_cluster/apache_2.4/htdocs/vh2/

        ServerName vh2.test.com

        ServerAdmin [e-mail]

        CustomLog "|/soft/apache/2.4/bin/rotatelogs /var/tests/p3_cluster/apache_2.4/log/vh2_access_%Y%m%d.log 86400" combined

        ErrorLog "|/soft/apache/2.4/bin/rotatelogs /var/tests/p3_cluster/apache_2.4/log/vh2_error_%Y%m%d.log 86400"

</VirtualHost>

- mod_cluster.conf

Has not changed since the first post.

Even like that, I still have the same behavior with CreateBalancers 0 or 2. JBoss cluster is reachable by both vhosts.

[jfclere]

According to your configuration any request is going to be on one of the VirtualHost... Nothing goes to the main server.

What are you trying to do?

[jjapache]

Actually I'm just trying to understand the difference between 'CreateBalancers 0' and 'CreateBalancers 2' .

If you have a test configuration that I can use to figure it out, I will be happy.

[jfclere]

After trying to reproduce it, it seems there is something wrong the proxy_server_conf is the same on all servers. Please create a mod_cluster JIRA for the problem.

[jjapache]

OK, it makes more sense now.

Here is the JIRA : [MODCLUSTER-430] CreateBalancers behave the same with option 0 or 2 - JBoss Issue Tracker

[jfclere]

After reviewing the problem in fact option 0 and 2 behave differently if only the VirtualHost contains a proxy directive. If the VirtualHost doesn't contain a proxy it is ignored by mod_proxy (and mod_cluster).

I have used:

CreateBalancers 0 / 2

# VirtualHost...

<VirtualHost 10.36.116.185:8000>

    ServerName 10.36.116.185

    ErrorLog "logs/error_log.10.36.116.185"

    CustomLog "logs/access_log.10.36.116.185" common

    ProxyRequests Off

</VirtualHost>

<VirtualHost 192.168.1.35:8000>

    ServerName 192.168.1.35

    ErrorLog "logs/error_log.192.168.1.35"

    CustomLog "logs/access_log.192.168.1.35" common

    ProxyRequests Off

</VirtualHost>

To validate the logic...
And check https://httpd.apache.org/docs/2.4/vhosts/examples.html  to get the VirtualHost logic right ;-)