Heartbeat

Heartbeat is an open source project that implements a heartbeat protocol. That is, messages are sent at regular intervals between machines and if a message is not received from a particular machine then the the machine is assumed to have failed and some form of evasive action is taken. Heartbeat can send heartbeat messages over zero or more serial links, zero or more serial links with PPP encapsulation, and zero or more ethernet interfaces.

When heartbeat is configured, a master node is selected. When heartbeat starts up this node sets up an interface for a virtual IP address, that will be accessed by external end users. If this node fails then another node in the heartbeat cluster will start up an interface for this IP address and use gratuitous ARP to ensure that all traffic bound for this address is received by this machine. This method of fail-over is called IP Address Takeover. Unless the nice_failback directive is set to on in the ha.cf file, once the master node becomes available again resources will fail-over again so they are once again owned by the master node.

Each virtual IP address is associated with a resource, a programme that Heartbeat will start on startup and stop on shutdown. Heartbeat allows arbitary resources to be used. Ultra Monkey uses ldirectord to run as a resource which run to monitor the availability of the real servers.

Copyright © 2000-2005, Horms
Last Updated: Tue May 17 17:37:24 2005 +0900

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