Using ACE for proxy server load balancing

gnijs · ‎04-06-2010

Hello groups,

I wanted to know your experiences of using ACE for proxy server load balancing.

I want to load balance to a pool of proxy servers. Note: load-balancing should be based on the HTTP URL (i can't use source or dest. ip address) so that

a certain domain always gets "cached/forwarded" to the same proxy server. I don't really want to put matching

criteria in the configuration (such as /a* to S1, /b* to S2, /c* to S3,etc..), but have this hash calculated automatically.

Can the ACE compute its own hash based on the number of "online" proxy servers ? ie. when 4 servers are online, distribute domains between 1,2,3,4 evenly.

Should server 4 fail, recalculate hash so that the load of S4 gets distributed across the other 3 evenly. Also load-balancing domains of S1 ,S2 and S3 should not change if S4 fails.....

regards,

Geert

Gilles Dufour · ‎04-07-2010

This is done with the following predictor command:

Scimitar1/Admin# conf t
Enter configuration commands, one per line. End with CNTL/Z.
Scimitar1/Admin(config)# serverfarm Proxy
Scimitar1/Admin(config-sfarm-host)# predictor hash ?
address         Configure 'hash address' Predictor algorithms
content         Configure 'hash http content' Predictor algorithms
cookie          Configure 'hash cookie' Predictor algorithms
header          Configure 'hash header' Predictor algorithm
layer4-payload Configure 'hash layer4-payload' Predictor algorithms
url             Configure 'hash url' Predictor algorithm
Scimitar1/Admin(config-sfarm-host)# predictor hash url

It does hash the url and the result takes into account the number of active proxies dynamically.

This command has been designed for this kind of scenario that you describe.

Gilles.