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From "Mohan Wickramasinghe" <mo...@roomsnet.com>
Subject Re: "Busy" in jkmanager
Date Wed, 05 Jul 2006 15:16:30 GMT
Thank you sir, for helping us again.
> Mohan2005 wrote:
>> Specifies what method load balancer is using for electing best worker.
>> If
>> method is set to R[equest] balancer will use number of requests to find
>> the
>> best worker. If set to T[raffic] balancer will use the network traffic
>> between JK and Tomcat to find the best worker. If set to B[usyness]
>> balancer
>> will pick the worker with the lowest current load, based on how many
>> requests the worker is currently serving. This number is divided by the
>> workers lbfactor, and the lowest value (least busy) worker is picked.
>>
>> And from your previous post you said..
>> and I quote..
>>
>> "Busy=number of parallel requests being processed for a worker at that
>> point
>> of time."
>> and where "request = HTTP Request in progress"
>>
>> Please clarify the difference between the 'Request' method and the
>> 'Busy'
>> method you had defined.
>
> All statements are true, but maybe confusing: For method "B" we only
> take into account the requests, that are being processed at the moment
> the next balancing decision has to be made (i.e. the next request comes
> in). So "B" will lead to nearly the same number of requests in work for
> every worker whenever you do a snapshot observation.
>
> For method "R" we accumulate, how many requests a worker has processed
> in the past. So "R" will lead to the same number of requests being
> accumulated by each worker, e.g. when you count that from your log files.
>
> Since the pure "R" strategy has negative side effects, we divide the
> number of requests done once a minute by 2, so that the past counts less
> the longer it is away.
>
>>
>> This is very important for us, since we currently use the 'Request'
>> method
>> in workers.properties and we want to know the exact working of the 2
>> methods
>> (Busy and Request). Since we plan on switching to a method that is best
>> suited for performance and proper load balancing.
>>
>
> Depending on the kind of workload B or r (or even T) could be better. B
> does the better Job on balancing parallelity, R does better balance
> accumulated work.
>
> Last minor point: B looks simpler and better understandable, but there
> is a small synchronization overhead with B, bevause B needs to change
> status counters 2 times per request (before and after), R only needs to
> add before and divide once in a minute.
>
>> Our main confusion here is that both the 'Request' and 'Busy' methods
>> refer
>> to the same criteria, which is "Number of Requests'
>
> I hope this sounds clearer now?
>
> Rainer
>
>
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>


Regards
Mohan Wickramasinghe


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