5.2. Components

Proxy Server

Shared Memory Manager module: mod_slotmem.so

The Shared Memory Manager module, mod_slotmem, makes the real-time worker node information available to multiple Apache HTTP Server 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 on which the proxy is listening for responses from nodes that wish to join the load-balancing cluster.

Worker Node Components

Worker node service: mod-cluster.sar

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.