Installation guide

Chapter 5. Overview
The JBoss HT TP Connector mod_clust er is a reduced-configuration, intelligent load-balancing solution
for JBoss Enterprise Application Platform, based on technology originally developed by the JBoss
mod_cluster community project.
The JBoss HT TP connector load-balances HT TP requests to JBoss Enterprise Application Platform
and JBoss Enterprise Web Server worker nodes, using Apache as the proxy server.
5.1. Key features
Apache HT TP Server-based
The JBoss HT TP Connector mod-clust e r uses Apache as the proxy server.
Real-t ime load-balancing calculation
The JBoss HT TP Connector mod_clust er creates a feedback network between the worker
nodes and the proxy server. T he mod_clust er service is deployed on each of the worker
nodes. T his service feeds real-time load information to the proxy server. T he proxy server then
makes intelligent decisions about where to allocate work, based on the current load on each
worker node. T his real-time adaptive load distribution results in increased optimization of
resources.
The information that is reported by the worker nodes and the load-balancing policy used by the
proxy are both customizable.
Routing based on rea l-time application life-cycle
The JBoss HT TP Connector mod_clust er service deployed on the worker nodes relays
application life-cycle events to the proxy server. This allows the server to dynamically update its
routing table. When an application is undeployed on a node, the proxy server no longer routes
traffic for that application to that node.
Automatic Proxy Discovery
The proxy server can be configured to announce its presence via UDP multicast. New worker
nodes discover the proxy server and add themselves to the load-balancing cluster
automatically. T his greatly reduces the configuration and maintenance needed. When UDP
multicast is not available or is undesirable, worker nodes are configured with a static list of
proxies.
Multiple Prot ocol Support
The JBoss HT TP Connector mod_clust er can use HT TP, HT TPS, or Apache JServ Protocol
(AJP) for communication between the proxy and the worker nodes.
5.2. Components
Proxy Server
On the proxy server, the JBoss HTT P Connector, mod-clust er, consists of four Apache modules.
Shared Memory Mana ger module: mod_slotmem.so
The Shared Memory Manager module, mod_slot mem, makes the real-time worker node
information available to multiple Apache server processes.
Cluste r Manager module: mod_manager.so
The Cluster Manager module, mod_manager, receives and acknowledges messages from
nodes, including worker node registrations, worker node load data, and worker node application
life-cycle events.
Proxy Balancer module: mod_proxy_cluster.so
The Proxy Balancer module, mod_proxy_clust er, handles the routing of requests to cluster
nodes. T he Proxy Balancer selects the appropriate node to forward the request to, based on
application location in the cluster, current state of each of the cluster nodes, and the Session ID
(if a request is part of an established session).
Proxy Advertisement module: mod_advertise.so
22 Chapter 5. Overview