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Configuring a local load balancer

note

This example demonstrates the tasks involved — it is not a recommendation for a production environment. Supporting a production load-balancing setup is outside iGrafx's scope and depends on your network and IT infrastructure.

This worked example uses Apache as a load balancer with mod_jk and sticky sessions, in front of two Tomcat cluster nodes on one Windows machine. SimpleTcpCluster (included with Tomcat) provides clustering, and DeltaManager replicates sessions across all nodes.

Prerequisites​

  • The iGrafx platform installed with the pre-deployed Tomcat (one installation per node).

Steps​

Configure the Tomcat nodes​

Edit each node's server.xml (in its \conf directory).

First node — keep the default ports (Connector 8080, Shutdown 8005, AJP 8009, Redirect 8443). If you change them, keep them unique across nodes. Uncomment the <Cluster> section so it reads:

<Engine name="Catalina" defaultHost="localhost" jvmRoute="worker1">
  <Cluster className="org.apache.catalina.ha.tcp.SimpleTcpCluster" channelSendOptions="8">
    <Manager className="org.apache.catalina.ha.session.DeltaManager" expireSessionsOnShutdown="false" notifyListenersOnReplication="true"/>
    <Channel className="org.apache.catalina.tribes.group.GroupChannel">
      <Membership className="org.apache.catalina.tribes.membership.McastService" address="228.0.0.4" port="45564" frequency="500" dropTime="3000"/>
      <Sender className="org.apache.catalina.tribes.transport.ReplicationTransmitter">
        <Transport className="org.apache.catalina.tribes.transport.nio.PooledParallelSender"/>
      </Sender>
      <Receiver className="org.apache.catalina.tribes.transport.nio.NioReceiver" address="auto" port="4000" autoBind="100" selectorTimeout="5000" maxThreads="6"/>
      <Interceptor className="org.apache.catalina.tribes.group.interceptors.TcpFailureDetector"/>
      <Interceptor className="org.apache.catalina.tribes.group.interceptors.MessageDispatch15Interceptor"/>
      <Interceptor className="org.apache.catalina.tribes.group.interceptors.ThroughputInterceptor"/>
    </Channel>
    <Valve className="org.apache.catalina.ha.tcp.ReplicationValve" />
    <ClusterListener className="org.apache.catalina.ha.session.ClusterSessionListener" />
  </Cluster>

Second node — if using the defaults, increase each port by 1 (Connector 8081, Shutdown 8006, AJP 8010, Redirect 8444). On different machines you don't need different ports. Uncomment the same <Cluster> section, but change jvmRoute to worker2.

You should now have two Tomcats running, reachable directly at ports 8080 and 8081.

Set up the Apache HTTP server​

  1. Download Apache (this example uses 2.4.18 x64) and unzip the Apache24 folder to C:\.

  2. Download the mod_jk binary (this example uses x86_64-httpd-2.4.x) and unzip it into \modules.

  3. In \logs, add two empty files: mod_jk.shm and mod_jk.log (skip if they're created automatically).

  4. In \conf\httpd.conf, change Listen 80 to Listen 8079 and ServerName localhost:80 to ServerName localhost:8079 (or your preferred unique port). Add these lines at the top:

    LoadModule jk_module C:\Apache24\modules\tomcat-connectors-1.2.40-windows-x86_64-httpd-2.4.x\mod_jk.so
    # Path to the worker configuration file
    JkWorkersFile C:\Apache24\conf\workers.properties
    # Where to store logging and memory-usage information
    JkShmFile C:\Apache24\logs\mod_jk.shm
    JkLogFile C:\Apache24\logs\mod_jk.log
    JkLogLevel info
    # Monitoring of the cluster
    JkMount /jkmanager/* jkstatus
    <Location /jkmanager>
        Require all granted
    </Location>
    # Map all requests to the web application to the load balancer
    JkMount /* LoadBalancer

    Then uncomment #LoadModule access_compat_module modules/mod_access_compat.so.

  5. In \conf, add a workers.properties file:

    # Virtual worker list
    worker.list=jkstatus, LoadBalancer
    # Enable virtual workers
    worker.jkstatus.type=status
    worker.LoadBalancer.type=lb
    # Add Tomcat instances as workers (2 in this example)
    worker.worker1.type=ajp13
    worker.worker1.host=localhost
    worker.worker1.port=8009
    worker.worker2.type=ajp13
    worker.worker2.host=localhost
    worker.worker2.port=8010
    # Provide the worker list to the load balancer
    worker.LoadBalancer.balance_workers=worker1,worker2
    worker.LoadBalancer.sticky_session=true

    The worker ports must match the AJP ports in each Tomcat's server.xml. This also sets sticky sessions — mod_jk defaults to true, but it's safer to set it explicitly.

  6. From Apache24's \bin directory, run httpd -k install.

  7. Run httpd -k start (use httpd -k stop to shut down).

  8. Open http://localhost:8079/ (or your load-balancer port) to reach the application through the load balancer. http://localhost:8079/jkmanager/ shows the load balancer and worker status; http://localhost:8079/manager → Server Status shows which node you're on by its port.

Add more nodes​

  1. Stop the Apache load balancer.
  2. Duplicate one of your Tomcat instance folders.
  3. Configure the new Tomcat node with unique ports (add 1 to the previous node's values).
  4. Add three lines to \conf\workers.properties for the new worker node.
  5. Start Apache again. Repeat as needed.