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4.2. Components
Proxy Server
On the proxy server, the JBoss HTTP Connector mod-cluster consists of four Apache modules.
- Shared Memory Manager:
mod_slotmem.so - The Shared Memory Manager module, mod_slotmem, makes the real-time worker node information available to multiple Apache server processes.
- Cluster 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_cluster, handles the routing of requests to cluster nodes. The 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 - The Proxy Advertisement Module, mod_advertise.so, broadcasts the existence of the proxy server via UDP multicast messages. The server advertisement messages contain the IP address and port number where the proxy is listening for responses from nodes that wish to join the load-balancing cluster.
Note
Refer to Section 5.1, “Apache Modules” for detailed information about the available modules including user-configurable parameters.
Worker Node Components
- Worker node service:
mod-cluster.sar - The JBoss HTTP Connector client service
mod-cluster.saris deployed on each worker node. This service provides the proxy with real-time information on the worker node's state and sends notification of application life cycle events; as well as allowing the node to discover and register itself with any proxies running on the same network.
