| | h1. Clustering \[fleXive\] |
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| | {toc:minlevel=2} |
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| | The \[fleXive\] framework is built from ground up to support clustered environments. All shared data and all caches are based on JBoss Cache, a distributed cache with transaction support. |
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| | On this page we will describe a basic 2-node setup with JBoss, using Apache 2.2 with mod_proxy for load balancing. |
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| | h2. Prerequisites |
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| | h3. Install \[fleXive\] |
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| | Install \[fleXive\] on (at least) 2 computers as described in the [installation guide|http://www.flexive.org/docs/website/jboss_installation.html], with the following deviations: |
| | * install into the *all* server profile instead of {{default}} (which is required for clustering) |
| | * install the external cache configuration file, as described in [Refining your configuration|http://www.flexive.org/docs/website/jboss_installation.html#jboss_installation_system_configuration_refining]. While this is not strictly necessary, it greatly simplifies setup since you do not have to repackage {{flexive.ear}} just to change the cache configuration. |
| | * [install the native Tomcat connectors|http://wiki.jboss.org/wiki/HowToAddAprToJBoss] for your operating system. At least in our cluster setups, these connectors turned out to be more reliable than the pure Java connectors. The DLLs/shared libraries should be put in the {{bin/native}} directory of your JBoss installation. |
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| | h3. Install Apache 2.2+ |
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| | Install the [Apache HTTP Server|http://httpd.apache.org/] version 2.2 or greater. Be sure that the {{mod_proxy}} and {{mod_proxy_ajp}} are included and enabled. |
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| | h2. Cluster Setup |
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| | h3. \[fleXive\] configuration |
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| | Apart from the installation instructions above, you can deploy the exact same version of \[flexive.ear\] on each cluster node . You might consider [farming deployment|http://www.jboss.org/file-access/default/members/jbossas/freezone/docs/Clustering_Guide/beta422/html/clustering-intro-farm.html] for easier updates, although it's not required. |
| | Just remember that all node members must use the same database host, which consequently needs to be reachable across the network (test this before starting \[fleXive\] since it's a very common issue). |
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| | h3. Tomcat configuration |
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| | We will setup a load-balancing cluster without _session replication_. This means that HTTP sessions will not be shared betweens cluster members, reducing overhead. Once a client has established a HTTP session with a cluster member, all future requests must be serviced from this member. This behaviour is called _session stickiness_. |
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| | To enable _session stickiness_, the Servlet container has to append a unique node ID to the {{JSESSIONID}} variable. On every JBoss installation, open {{$\{jboss.home}/server/all/deploy/jboss-web.deployer/server.xml}} and set the node ID in the {{jvmRoute}} attribute of the {{Engine}} tag, e.g. |
| | {code} |
| | <Engine name="jboss.web" defaultHost="localhost" jvmRoute="node1"> |
| | {code} |
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| | When a request is served by the cluster, this node ID is appended to the session ID (e.g."{{JSESSIONID=ECB99E48A4A0129127085A3711465D22.node1}}"). |
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| | h3. mod_proxy configuration |
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| | Now that we have a cluster of JBoss nodes we need a _load balancer_ to distribute requests between the cluster members. A basic software solution is Apache's mod_proxy. It can connect to Tomcat using the binary AJP1.3 protocol, which should be a good deal faster than HTTP. You need to enable the following modules (on Unix, create symlinks from {{/etc/apache2/mods-available}} to {{/etc/apache2/mods-enabled}}): |
| | * {{proxy.load}} |
| | * {{proxy_ajp.load}} |
| | * {{proxy_balancer.load}} |
| | * {{status.load}} |
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| | Following the [mod_proxy documentation|http://httpd.apache.org/docs/2.0/mod/mod_proxy.html], we define two nodes: |
| | * {{node1}} on 192.168.1.40 and |
| | * {{node2}} on 192.168.1.41. |
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| | An example configuration that clusters the {{/flexive}} and {{/products}} applications (add the code to your {{apache2.conf}}): |
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| | {code} |
| | ProxyRequests Off |
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| | <Proxy *> |
| | Order deny,allow |
| | Allow from all |
| | </Proxy> |
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| | ProxyPreserveHost On |
| | ProxyPass /products balancer://my_cluster/products stickysession=JSESSIONID nofailover=On |
| | ProxyPass /flexive balancer://my_cluster/flexive stickysession=JSESSIONID nofailover=On |
| | |
| | <Proxy balancer://my_cluster> |
| | BalancerMember ajp://192.168.1.40:8009 route=node1 loadfactor=1 |
| | BalancerMember ajp://192.168.1.41:8009 route=node2 loadfactor=1 |
| | </Proxy> |
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| | <Location /balancer> |
| | SetHandler balancer-manager |
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| | Order Deny,Allow |
| | Deny from all |
| | Allow from all |
| | </Location> |
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| | ProxyStatus On |
| | <Location /status> |
| | SetHandler server-status |
| | |
| | Order Deny,Allow |
| | Deny from all |
| | Allow from all |
| | </Location> |
| | {code} |
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| | The most interesting part is the balancer setup: |
| | {code} |
| | <Proxy balancer://my_cluster> |
| | BalancerMember ajp://192.168.1.40:8009 route=node1 loadfactor=1 |
| | BalancerMember ajp://192.168.1.41:8009 route=node2 loadfactor=1 |
| | </Proxy> |
| | {code} |
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| | The node name specified in {{route}} must match the identifier set in the {{jvmRoute}} attribute of this node's Tomcat instance (see Tomcat configuration). The {{loadfactor}} determines how the requests will be distributed: in this case, both nodes are assumed to be equal and capable of handling the same number of requests. If you used {{loadfactor=2}} on node1, this would mean that for every request routed to node2, two would be routed to node1. |
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| | After restarting Apache, you should be able to access the clustered applications on your Apache host under {{/products/}} and {{/flexive/}}. You can also show the cluster status pages at {{/status/}} and {{/balancer/}}. |
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| | h2. Cluster operation |
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| | h3. Starting cluster nodes |
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| | When starting a JBoss instance, bind it to the external IP address and specify the cluster partition name and IP addresses to identify the members of your cluster. For example, to bind the JBoss instance on {{192.168.1.40}} to the external address and specify cluster membership parameters: |
| | {code}run.sh -c all -b 192.168.1.40 -Djboss.partition.name=flexiveCluster |
| | -Djboss.partition.udpGroup=228.2.3.8 -Djboss.hapartition.mcast_port=38241{code} |
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| | h3. Stopping cluster nodes |
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| | | In this setup, we did not enable session replication of JBoss. Since all JSF applications are bound to HTTP sessions, stopping a cluster node will destroy all sessions of this cluster. However, it will join the cluster automatically if it is started again. |
| | | In this setup, we did not enable session replication of JBoss. Since all JSF applications are bound to HTTP sessions, stopping a cluster node will destroy all sessions of this node. However, it will join the cluster automatically if it is started again. |
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| | h2. Resources |
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| | [JBoss Server Clustering Guide|http://www.jboss.org/file-access/default/members/jbossas/freezone/docs/Clustering_Guide/beta422/html/index.html] |
| | [Apache mod_proxy documentation|http://httpd.apache.org/docs/2.0/mod/mod_proxy.html] |
