One single balancer-manager page for multiple virtual hosts

Question

We're using currently an Apache 2.4 as load-balancer for a multi-master-cluster of three Tomcats-Servers. We can access the internal IP-Address of this load-balancer with an web-browser and change the settings on the fly (e.g. http://xx.xx.xx.xx/balancer-manager). This works and we're pretty fine with this.

Enabled modules:

• proxy.load (proxy.conf used to configure)
• proxy_ajp.load
• proxy_balancer.load (proxy_balancer.conf used to configure)

But now we will host several (three in this setup) virtual hosts on this Apache, each representing a cluster of three Tomcats itself. Each is accessiable via an URL like http://customer.company.tld/app/ui). So the path is the same for each cluster! Now we're facing two problems:

• The page balancer-manager is only reachable via it's virtual host. Therefore we have to access the balancer-manager via random choosen internal hostname (added to ServerAlias) and add this hostname also into the /etc/hosts off our internal computers to be be able to use it.
• Furthermore we have to do this for each virtual-host (~cluster). But we want a single page balancer-manager which presents all virtual-hosts and the cluster behind.

Here some sample configuration:
/etc/apache2/site-enabled/foo # we have actually three of them: foo, bar, baz

<VirtualHost *:80>
    ServerAdmin webmaster@localhost
    ServerName customer-foo.company.tld
    ServerAlias customer-foo-balancer customer-foo.company.tld www.customer-foo.company.tld

    DocumentRoot /var/www

        <Directory />
                Options FollowSymLinks
                AllowOverride None
                Order allow,deny
                deny from all
        </Directory>
        <Directory /var/app/app_static>
                Options Indexes FollowSymLinks MultiViews
                AllowOverride All
                Order allow,deny
                allow from all
        </Directory>
        <Directory /var/www/app_static_res>
                Options Indexes FollowSymLinks MultiViews
                AllowOverride All
                Order allow,deny
                allow from all
        </Directory>

    # load balancer
        <Location /balancer-manager>
                 SetHandler balancer-manager
                 Order deny,allow
                 Deny from all
                 # allows for internal access
                 Allow from 127.0.0.1 ::1 10.1.21.81 10.1.4.9
                 Satisfy all
        </Location>

        ProxyRequests Off
        ProxyVia Off
        ProxyPreserveHost On

        <Proxy balancer://htg>
                ProxySet failonstatus=503
                BalancerMember ajp://10.171.23.120:8010/app lbset=0 route=foo001 loadfactor=40
                BalancerMember ajp://10.171.23.121:8010/app lbset=0 route=foo002 loadfactor=40
                BalancerMember ajp://10.171.23.122:8010/app lbset=0 route=foo003 loadfactor=20
        </Proxy>

        <Proxy balancer://htgservice>
                ProxySet failonstatus=503
                BalancerMember ajp://10.171.23.120:8011/wcs_service route=foo001 loadfactor=40
                BalancerMember ajp://10.171.23.121:8011/wcs_service route=foo002 loadfactor=40
                BalancerMember ajp://10.171.23.122:8011/wcs_service route=foo003 loadfactor=20
        </Proxy>


        ProxyPass        /app balancer://foo stickysession=JSESSIONID|jsessionid nofailover=Off scolonpathdelim=On
        ProxyPassReverse /app balancer://foo

        ProxyPass        /app_service  balancer://fooservice stickysession=JSESSIONID|jsessionid nofailover=Off scolonpathdelim=On
        ProxyPassReverse /app_service  balancer://fooservice

        LogLevel warn

    ErrorLog ${APACHE_LOG_DIR}/error.log
    CustomLog ${APACHE_LOG_DIR}/access.log combined
</VirtualHost>

In the past we configured the balancing inside the distinct files proxy.conf and proxy_balancer.conf, which should allow for accessing via the internal IP and show up all clusters and cluster-members on a single page. But this won't work anymore, the configuration for proxies seem to accept only paths (e.g. app and app_service) not URLs or hostnames. We can't and won't change the paths. Therefore we moved the proxy-configuration inside the virtual hosts.

Thanks for your help!

Solution 1

What about splitting your config. Put your balancer definition outside any virtual host and remove the context:

     <Proxy balancer://htg>
            ProxySet failonstatus=503
            BalancerMember ajp://10.171.23.120:8010 lbset=0 route=foo001 loadfactor=40
            BalancerMember ajp://10.171.23.121:8010 lbset=0 route=foo002 loadfactor=40
            BalancerMember ajp://10.171.23.122:8010 lbset=0 route=foo003 loadfactor=20
    </Proxy>

    <Proxy balancer://htgservice>
            ProxySet failonstatus=503
            BalancerMember ajp://10.171.23.120:8011 route=foo001 loadfactor=40
            BalancerMember ajp://10.171.23.121:8011 route=foo002 loadfactor=40
            BalancerMember ajp://10.171.23.122:8011 route=foo003 loadfactor=20
    </Proxy>

In your vhosts reference these balancers:

ProxyPass        /app balancer://htg/app stickysession=JSESSIONID|jsessionid nofailover=Off scolonpathdelim=On
ProxyPassReverse /app balancer://htg/app

ProxyPass        /app_service  balancer://htgservice/wtg_service stickysession=JSESSIONID|jsessionid nofailover=Off scolonpathdelim=On
ProxyPassReverse /app_service  balancer://htgservice/wtg_service

To access your balancer-manager, create an extra management vhost with <Location /balancer-manager> in it.

This way, you have one place where all your balancers are defined and one vhost to access the balancer-manager which shows you all your balncers.

Solution 2

Thank you Christian! The solution of Christian is correct!

Basically you have to put ProxyPass and ProxyPassReverse inside the configuration for the Virtual-Hosts, and define the Proxy-Directive in the proxy.conf. As Christian already stated in his own comments, it is required use the ProxySet-Directive inside the Proxy-Directive to configure the StickySessions - it won't work with ProxyPass. Bellow is a short, but complete, example:

Sample VirtualHost (one for foo, bar, baz):

<VirtualHost *:80>
    ServerAdmin webmaster@localhost
    ServerName customer-foo.company.tld
    ServerAlias customer-foo-balancer customer-foo.company.tld www.customer-foo.company.tld

    DocumentRoot /var/www/foo

    <Directory />
        Options FollowSymLinks
        AllowOverride None
        Order allow,deny
        deny from all
    </Directory>
    <Directory /var/www/foo/wcs_static>
        Options Indexes FollowSymLinks MultiViews
        AllowOverride All
        Order allow,deny
        allow from all
     </Directory>
     <Directory /var/www/foo/wcs_static_res>
        Options Indexes FollowSymLinks MultiViews
        AllowOverride All
        Order allow,deny
        allow from all
     </Directory>

    # maintenance
    RewriteEngine On

    RewriteCond %{DOCUMENT_ROOT}/wcs_static_res/maintenance.html -f
    RewriteCond %{REQUEST_FILENAME} !/wcs_static_res/maintenance.html
    RewriteCond %{REQUEST_FILENAME} !/wcs_static_res/maintenance-time.png
    RewriteCond %{REMOTE_HOST} !^10\.1\.0\.203
    RewriteRule ^.*$    /wcs_static_res/maintenance.html [L]

    # redirect, SSL itself is handled by another server in front of this loadbalancer
    RedirectMatch (.*)/$  https://customer-foo.company.tld/wcs/ui

    # load balancer

    # web-frontend
    ProxyPass        /wcs balancer://foo
    # stickysession can't be set with ProxyPass in this case, see proxy.conf
    ProxyPassReverse /wcs balancer://foo

    # standalone-clients 
    ProxyPass        /wcs_service balancer://fooservice
    ProxyPassReverse /wcs_service balancer://fooservice


    # logging
    LogLevel warn
    ErrorLog ${APACHE_LOG_DIR}/foo_error.log
    CustomLog ${APACHE_LOG_DIR}/foo_access.log combined
</VirtualHost>

proxy.conf (there is only this one):

<IfModule mod_proxy.c>

        ProxyRequests Off
        ProxyVia Off
        ProxyPreserveHost On

        <Proxy balancer://foo>
                # stickysessions must be defined here
                ProxySet failonstatus=503 stickysession=JSESSIONID|jsessionid nofailover=Off scolonpathdelim=On
                BalancerMember ajp://10.171.23.120:8010/wcs lbset=0 route=foo001 loadfactor=40
                BalancerMember ajp://10.171.23.121:8010/wcs lbset=0 route=foo002 loadfactor=40
                BalancerMember ajp://10.171.23.122:8010/wcs lbset=0 route=foo003 loadfactor=20
        </Proxy>
        <Proxy balancer://fooservice>
                ProxySet failonstatus=503 stickysession=JSESSIONID|jsessionid nofailover=Off scolonpathdelim=On
                BalancerMember ajp://10.171.23.120:8011/wcs_service route=foo001 loadfactor=40
                BalancerMember ajp://10.171.23.121:8011/wcs_service route=foo002 loadfactor=40
                BalancerMember ajp://10.171.23.122:8011/wcs_service route=foo003 loadfactor=20
        </Proxy>

        <Proxy balancer://bar>
                ProxySet failonstatus=503 stickysession=JSESSIONID|jsessionid nofailover=Off scolonpathdelim=On
                BalancerMember ajp://10.171.21.110:8010/wcs lbset=0 route=bar001 loadfactor=40
                BalancerMember ajp://10.171.21.111:8010/wcs lbset=0 route=bar002 loadfactor=40
                BalancerMember ajp://10.171.21.112:8010/wcs lbset=0 route=bar003 loadfactor=20
        </Proxy>
        <Proxy balancer://barservice>
                ProxySet failonstatus=503 stickysession=JSESSIONID|jsessionid nofailover=Off scolonpathdelim=On
                BalancerMember ajp://10.171.21.110:8011/wcs_service route=bar001 loadfactor=40
                BalancerMember ajp://10.171.21.111:8011/wcs_service route=bar002 loadfactor=40
                BalancerMember ajp://10.171.21.112:8011/wcs_service route=bar003 loadfactor=20
        </Proxy>

        <Proxy balancer://baz>
                ProxySet failonstatus=503 stickysession=JSESSIONID|jsessionid nofailover=Off scolonpathdelim=On
                BalancerMember ajp://10.171.45.100:8010/wcs lbset=0 route=baz001 loadfactor=40
                BalancerMember ajp://10.171.45.101:8010/wcs lbset=0 route=baz002 loadfactor=40
                BalancerMember ajp://10.171.45.102:8010/wcs lbset=0 route=baz003 loadfactor=20
        </Proxy>

        <Proxy balancer://bazservice>
                ProxySet failonstatus=503 stickysession=JSESSIONID|jsessionid nofailover=Off scolonpathdelim=On
                BalancerMember ajp://10.171.45.100:8011/wcs_service route=baz001 loadfactor=40
                BalancerMember ajp://10.171.45.101:8011/wcs_service route=baz002 loadfactor=40
                BalancerMember ajp://10.171.45.102:8011/wcs_service route=baz003 loadfactor=20
        </Proxy> 
</IfModule>

proxy_balancer.conf:

<IfModule mod_proxy_balancer.c>
        <IfModule mod_status.c>
        <Location /balancer-manager>
                SetHandler balancer-manager
                Order deny,allow
                Deny from all
                # store here your internal IPs for direct access
                Allow from 127.0.0.1 ::1
                Satisfy all
        </Location>

</IfModule>

Now you can change the configuration through http://ipofloadbalancer.com/balancer-manager for all servers behind your proxy. No need to hack with /etc/hosts on the clients and the loadbalancer. Drawback, especially with the Apache 2.4, the interface gets quickly cluttered and you have to scroll much.

Comments

[Peter Weber]

Thanks. I will try that as soon as possible! Till now, I thought this kind of split isn't possible and assumend I can work around this with a weird kind of rewrite.

[user2987902]

I found one drawback. It seems it is not working correctly with stickysessions enabled.

[user2987902]

Perhaps, this is a solution to the sticky session problem: stackoverflow.com/a/9951315/252730

[user2987902]

It is also discribed in this httpd bug report: issues.apache.org/bugzilla/show_bug.cgi?id=39304

[Peter Weber]

Hi! I already hit this problem yesterday. The styicksessions must be defined with ProxySet inside the <Proxy></Proxy> and it works!