On 20.04.2009 15:57, Jim Jagielski wrote: > > On Apr 17, 2009, at 4:28 PM, Rainer Jung wrote: >> >> The same type of balancing decision algorithm was part of mod_jk between >> 1.2.7 and 1.2.15. I always had problems to understand, how it exactly >> behaves in case some workers are out of order. The algorithm is >> interesting, but I found it very hard to model its mathematics into >> formulas. >> >> We finally decided to switch to something else. For request, traffic or >> session based balancing we do count items (requests, bytes or new >> sessions), and divide the counters by two once a minute. That way load >> that happened in the past does count less. >> >> Furthermore a worker that was dead or deactivated some time gets the >> biggest current load number when being reactivated, so that it starts a >> smooth as possible. >> >> I expect porting this to mod_proxy in trunk will be easy, but I'm not >> sure what experience others have with the fairness of balancing in case >> you add dynamics to the workers (errors and administrative downtimes). >> > > I have some ideas on the "soft start" when a errored-out worker > returns (or when a new worker is added *hint* *hint*) that I've > been playing with. The main thing, for me at least, is low overhead, > even if it means sacrificing accuracy to the nth decimal place... > I used to think aging was not something we wanted to do in > mod_proxy, but mostly it was based on complex aging, and the > overhead associated with that. But I have some ideas there as > well. > > The main thing I've been working on is trying to do all these > things in trunk in a way that is "easily" backportable to 2.2...
So that makes my answer to JFC partially obsolete. Sorry I read your post later. Regards, Rainer
