Great info Rainer - thanks very much. Ian
> -----Original Message----- > From: Rainer Jung [mailto:[EMAIL PROTECTED] > Sent: 21 June 2007 16:53 > To: Tomcat Users List > Subject: Re: Two IIS web servers > > Phi-Long LE wrote: > > Ian, > > > > reading optional directives you should probably use the > > worker.xxx.method, its value is Request, session, traffic or busyness > > Default is request. For most use cases this should work best. > > How does it work? > > 1) Multiple Web server instances do not share any information about > load. So they decide completely independently. > > 2) request method: mod_jk counts the requests going to each worker and > whenever a request has no session associated it chooses the worker with > the smallest number. The first request after every 60 seconds will > trigger a maintenance cycle, which divides all counters by 2, such that > historic data gets less important. If you use load factors, the > counters > get adjusted by the load factors. Bigger load factors will result in > bigger load (and smaller increments to the counters). > > 3) If a worker comes back after error, it will start with the biggest > of > the actual counters, to prevent it from getting a request storm. > > 4) busyness method: this looks at the number of request which are > actually in the middle of processing. Could be OK for download sites, > but usually does not work that well. Especially bad, if your side is > not > high traffic. > > 5) traffic: the same as request method, but counts bytes transferred > instead of requests done. The bytes are only added after the requests > have finished, so if you have long running downloads, the byte counters > will ot change for a long time and then change a lot. > > Having multiple instances work independently should be no problem, if > statistics count: this means: you have a lot of traffic, and the > percentage of requests without sessions is not too small. In other > words: you have a lot of users and the sessions are not taking to long. > > Load balancing might run into asymmetries, if you have very long > lasting > in house sessions and very different types of users. Then some heavily > used sessions might produce the most load. > > On the other hand: as long as you only operate two backends, the > quality > of the load balancing might not be very important, because out of > availybility considerations usually one of the two nodes should be able > to handle the maximum load. :) > > Regards, > > Rainer > > > > > Le 21/06/2007 16:00, Ian Buzer a écrit : > >> Thanks for that Rainer. > >> > >> How about when a new session comes in? Does mod_jk obtain > information > >> from > >> each Tomcat about its current load, or does it base it on the number > of > >> requests that that particular instance of mod_jk has forwarded to > >> Tomcat? If > >> it's the latter, is this likely to cause problems? > >> > >> Thanks > >> Ian > >> > >> > >> > >> > >>> -----Original Message----- > >>> From: Rainer Jung [mailto:[EMAIL PROTECTED] > >>> Sent: 21 June 2007 15:50 > >>> To: Tomcat Users List > >>> Subject: Re: Two IIS web servers > >>> > >>> Yes, this will work. The only bad thing will be, that the requests > >>> belonging to one session will be logged partially on both of the > IIS > >>> instances, so if you try to debug a problem, you always need to > look at > >>> both IIS servers. > >>> > >>> Stickyness works like this: > >>> > >>> - you set a unique jvmRoute in the engine element of server.xml > >>> - Tomcat appends the jvmRoute to each sessionid it generated, with > a > >>> dot > >>> as a separator > >>> - mod_jk load balancer looks for a session id whenever it receives > a > >>> request and strips of the routing string behind the dot > >>> - if mod_jk finds such a routing strings, the load balancer > searches > >>> for > >>> a worker with the same name or with a route attribute with the same > >>> value and sends it there > >>> > >>> So mod_jk does not hold any state information about where which > session > >>> lies. Every request carries the information with it. > >>> > >>> Regards, > >>> > >>> Rainer > >>> > >>> Ian Buzer wrote: > >>> > >>>> Hi, > >>>> > >>>> I currently have one IIS server balancing requests to two Tomcats > >>>> > >>> using JK > >>> > >>>> 1.2. I am using JK to provide sticky sessions and all is working > >>>> > >>> well. > >>> > >>>> I would like to be able share requests across a second IIS server, > >>>> > >>> however I > >>> > >>>> am unable to create sticky sessions at the web server level so > >>>> > >>> requests > >>> > >>>> could go to either web server. > >>>> > >>>> My question is, if I point both IIS servers to both Tomcats, will > >>>> > >>> this work > >>> > >>>> correctly? Will the sessions still get directed to the correct > >>>> > >>> Tomcat, and > >>> > >>>> will the two JKs still be able to choose the best worker for new > >>>> > >>> sessions? > >>> > >>>> Many thanks > >>>> Ian > > --------------------------------------------------------------------- > To start a new topic, e-mail: users@tomcat.apache.org > To unsubscribe, e-mail: [EMAIL PROTECTED] > For additional commands, e-mail: [EMAIL PROTECTED] > --------------------------------------------------------------------- To start a new topic, e-mail: users@tomcat.apache.org To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
