Which load balancer?

Question

I am looking for a load balancer that:

• Is good stuff (free, open source, documented)
• Handles SSL
• Workers register in the load balancer, instead of listing workers (like jboss mod_cluster)
• works with apache tomcat (unlike jboss mod_cluster)

Anyone knows a load balancer that can do this?

Answer 1

ServerFault uses HAProxy (free, open source, handles SSL w/stunnel, runs tests against clustered servers instead of waiting for clustered servers to register, and supports a wide variety of configurations).

Here's an HAProxy/Tomcat howto if you're interested in trying it out.

Answer 2

You can use mod_cluster with Tomcat 6+. Mod_cluster 1.2.1+ works good :-) Follow: http://docs.jboss.org/mod_cluster/1.2.0/html_single/

EDIT: [Scott Pack, Sep 24 at 17:01] was right, here you go: Apache uses multicast for advertiding its presence to potential worker nodes. These worker nodes send messages to the Apache balancer. These messages contain available contexts, session settings and current load calculated on the worker node.

E.g.

Apache configuration:

<IfModule manager_module>
    Listen mybox:8888
    ManagerBalancerName mycluster
    <VirtualHost mybox:8888>
        <Location />
         Order deny,allow
         Deny from all
         #Security concern...
         Allow from all
        </Location>

        AdvertiseGroup 224.0.1.105:6666
        EnableMCPMReceive

        <Location /mcm>
           SetHandler mod_cluster-manager
           Order deny,allow
           Deny from all
           #Security concern :-)
           Allow from all
        </Location>

        SSLEngine on
        SSLCipherSuite AES128-SHA:ALL:!ADH:!LOW:!MD5:!SSLV2:!NULL
        SSLCertificateFile /meh/httpd/certs/Server/server.crt
        SSLCertificateKeyFile /meh/httpd/certs/Server/server.key
        SSLCACertificateFile /meh/httpd/certs/Server/myca.crt
        SSLVerifyClient require
        SSLVerifyDepth  10

    </VirtualHost>
</IfModule>

Tomcat6 configuration in server.xml:

<Listener
    className="org.jboss.modcluster.container.catalina.standalone.ModClusterListener"
    advertise="true"
    advertiseGroupAddress="224.0.1.105"
    advertisePort="6666"
    stickySession="true"
    stickySessionForce="false"
    stickySessionRemove="true"

    ssl="true"
    sslKeyStorePass="tomcat"
    sslKeyStore="/meh/tomcat6/certs/Client/test.p12"
    sslKeyStoreType="PKCS12"
    sslTrustStore="/meh/tomcat6/certs/Client/ca.p12"
    sslTrustStoreType="PKCS12"
    sslTrustStorePassword="tomcat"

    loadMetricClass="org.jboss.modcluster.load.metric.impl.BusyConnectorsLoadMetric"
    loadMetricCapacity="1"
    loadHistory="9"
    loadDecayFactor="2"
/>

The aforementioned Tomcat worker will:

• listen for balancer advertising and register with any balancer it finds
• use sticky sessions, yet failover to another worker is permitted (stickySessionForce="false")
• use ssl authentication with certificates (Apache<->SSL<->Tomcats)
• use BusyConnectorsLoadMetric, that basically measures number of threads being busy serving requests

HTH

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