On Mon, 2006-31-07 at 19:34 +0200, Graham Leggett wrote: > Users of mod_backhand (for httpd v1.3) would disagree, it's a similar
Greenspun: http://philip.greenspun.com/scratch/scaling.adp Asks the right question: How are load balancers actually built? and suggests: zeus, mod_backhand, and router solutions but unfortunately does not give a direct answer. However, two paragraphs down: Failover from a broken load balancer to a working one is essentially a network configuration challenge, beyond the scope of this textbook. Basically what is required are two identical load balancers and cooperation with the next routing link in the chain that connects your server farm to the public Internet. Those upstream routers must know how to route requests for the same IP address to one or the other load balancer depending upon which is up and running. What keeps this from becoming an endless spiral of load balancing is that the upstream routers aren't actually looking into the TCP packets to find the GET request. They're doing the much simpler job of IP routing. This points up the difficulty of trying to solve the problem at the application level. My point was that free routing solutions to this problem were already available since 1997. > solution that has been around for years. The lb support in v2.x will The mod_backhand site seems to date since 2000 and Greenspun's article is dated 2003, which also seems to be the latest release of mod_backhand ... > hopefully eventually allow users of mod_backhand to migrate to v2.x > from > v1.3. ... it certainly seems to be important to create the migration path but you have yet to convince me that the scalability is the same. However, you have certainly convinced me to try the apache solution once it is available ... I have a customer who might need it in a year or so. -- --gh
