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From Jean-frederic Clere <>
Subject Re: mod_proxy_balancer/mod_proxy_ajp TODO
Date Thu, 22 Jun 2006 14:05:09 GMT
Henri Gomez wrote:

> The TomcatoMips indicator was just something to tell that it's not the
> raw CPU power which is important, but the estimated LOAD capacity of
> an instance.
> Accounting informations should included average time to execute a
> request, number of thread in use (AJP/HTTP), estimated free memory...
> Just to be sure that when a tomcat (for example), is near overload,
> the next requests will be routed to another less loaded tomcat.

If you want such information I think Tomcat (or the backend server) has 
to provide it.



> 2006/6/22, Darryl Miles <>:
>> Henri Gomez wrote:
>> > Well you we always indicate some sort of CPU power for a remote (a 
>> sort
>> > of bogomips) and use this in computation.
>> Why should the CPU power matter, what if the high power CPU is getting
>> all the complex requests and the lower power CPU is ending up with
>> simple request (static content).
>> You are better implementing it in control packets over AJP that can
>> advertise that hosts current willingness to take on new requests on a
>> 32/64bit scale.  Call this a "flow control back pressure packet", a
>> stateless beacon of information which may or may not be used by the
>> client AJP.
>> Then have a pluggable implementation at the server end of calculating
>> that value and frequency for advertising it.  All the apache LB has to
>> do is work from that load calculation.  All existing AJPs have to do is
>> just ignore the packet.
>> In the case of different horse power CPUs that factor is better fed into
>> the server AJP algorithm by biasing the advertised willingness to take
>> on new requests after a certain low level is reached.  Only the server
>> end of the AJP know the true request rate and how near that system is to
>> breaking point.
>> This scheme also works where apache may not see all the work the backend
>> is doing, like if you have a different apache front end clusters linked
>> to the same single backend cluster.
>> Darryl

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