Abstract

HotSwap is a program that provides transparent failover for existing UNIX servers without modification or special hardware. HotSwap runs two instances of a server on independent machines in sync, so that if either machine fails, the other may assume control without breaking TCP connections or losing application state. Replication and failover is transparent to both clients and servers. Servers are not aware that a backup replica is maintaining state. Clients are unaware that a backup server has taken over from a failed master. This system is applicable to a wide variety of common servers including Java, Apache, and PostgreSQL and other servers that may have no other mechanisms for fault tolerance.

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