Chapter 6. Clustering
Chapter 6. Clustering Support for Keepalived and HAProxy Load Balancer technology Red Hat Enterprise Linux 6.6 provides support for Load Balancer technology with Keepalived and HAProxy . Keepalived provides simple and robust facilities for load balancing and high availability. The load-balancing framework relies on the well-known and widely used Linux Virtual Server kernel module providing Layer-4 (transport layer) load balancing. Keepalived implements a set of checkers to dynamically and adaptively maintain and manage a load balanced server pool according to their health. Keepalived also implements the Virtual Router Redundancy Protocol (VRRPv2) to achieve high availability with director failover. HAProxy is a TCP/HTTP reverse proxy which is particularly suited for high availability environments. HAProxy can: Route HTTP requests depending on statically assigned cookies; Spread the load among several servers while assuring server persistence through the use of HTTP cookies; Switch to backup servers in the event a main server fails; Accept connections to special ports dedicated to service monitoring; Stop accepting connections without breaking existing ones; Add, modify, and delete HTTP headers in both directions; Block requests matching particular patterns; Persist client connections to the correct application server depending on application cookies; Report detailed status as HTML pages to authenticated users from a URI intercepted from the application.