Re: load balancing problems

frank bretschneider wrote:
> hi ..
> 
> i am using mod_backhand to load balance a server cluster.
> somehow it does not really balance the load of the servers.
> 
> my rules are ...
> 
> <Directory /www/htdocs>
> Backhand removeSelf
> Backhand byAge
> Backhand byLoad
> Backhand byRandom

Here you tell it to randomly assign traffic.  So it will.  I would suggest 
taking the byRandmon out.  With 4 servers and a front end, I would try 
something like:

Backhand removeSelf
Backhand byAge
Backhand byBusyChildren

Load is a slowly adjusting metric and not very well suited to web traffic.  As 
a thousand requests could come to a single machine over a few second period 
and the load will not update to reflect that workload for several more seconds 
and not fully for a minute.

BusyChildren is designed to be a "point in time" run queue length estimator 
based on the number of occupied Apache children.  It isn't perfect, but tests 
show that it works very well.

> # Backhand byBusyChildren
> </Directory>
> 
> i am using one apache front server and 4 apache backhand servers.
> three backhand servers have almost the same hardware. the 4th server
> has the slowest hardware. this server gets a real high load a lot of
> times. so the rule "by Load" does not seam to work.
> 
> as a work around i would like to reduce the max amount of clients on
> this slow machine. does anybody know if the frontserver will recognize
> if the max. amount of clients is reached on a backhanded server and
> will not forward any requests to this server till there is a new client
> available.
> 
> thx.
>

-- 
Theo Schlossnagle
Principal Consultant
OmniTI Computer Consulting, Inc. -- http://www.omniti.com/
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