Hosting a network service on a cluster of servers using a single-address image

摘要

Methods and apparatus for hosting a network service on a cluster of servers, each including a primary and a secondary Internet Protocol (IP) address. A common cluster address is assigned as the secondary address to each of the servers in the cluster. The cluster address may be assigned in UNIX-based servers using an ifconfig alias option, and may be a ghost IP address that is not used as a primary address by any server in the cluster. Client requests directed to the cluster address are dispatched such that only one of the servers of the cluster responds to a given client request. The dispatching may use a routing-based technique, in which all client requests directed to the cluster address are routed to a dispatcher connected to the local network of the server cluster. The dispatcher then applies a hash function to the client IP address in order to select one of the servers to process the request. The dispatching may alternatively use a broadcast-based technique, in which a router broadcasts client requests having the cluster address to all of the servers of the cluster over a local network. The servers then each provide a filtering routine, which may involve comparing a server identifier with a hash value generated from a client address, in order to ensure that only one server responds to each request broadcast by the router.