Question about source IP persistence (balance source) when a server goes down:

From: Malcolm Turnbull <>
Date: Fri, 16 Jan 2009 14:48:18 +0000

The manual states that when using balance source:

"The source IP address is hashed and divided by the total weight of the running servers to designate which server will receive the request. This ensures that the same client IP address will always reach the same server as long as no server goes down or up. If the hash result changes due to the number of running servers changing, many clients will be directed to a different server. This algorithm is generally used in TCP mode where no cookie may be inserted. It may also be used on the Internet to provide a best-effort stickyness to clients which refuse session cookies. This algorithm is static, which means that changing a server's weight on the fly will have no effect."

Does this mean that if say 1 server out of a cluster of 5 servers fails, then it is likely
that the hash result changes and lots of the clients could potentially loose their session? (i..e hit the wrong server because the hash has changed)


Malcolm Turnbull. Ltd.
Phone: +44 (0)870 443 8779
Received on 2009/01/16 15:48

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