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From Jim Jagielski <...@jaguNET.com>
Subject Re: The Case for a Universal Web Server Load Value
Date Thu, 15 Nov 2012 11:59:51 GMT

On Nov 14, 2012, at 5:19 PM, Ask Bjørn Hansen <ask@develooper.com> wrote:

> 
> On Nov 14, 2012, at 11:01, Tim Bannister <isoma@jellybaby.net> wrote:
> 
>>> I really like how Perlbal does it:
>>> 
>>> It opens a connection when it thinks it needs more and issues a (by default,
it's configurable) "OPTIONS *" request and only after getting a successful response to the
test will it send real requests on that connection (and then it will keep the connection open
with Keep-Alive for further requests).
>> 
>> X-Server-Load: would still be an improvement, eg with this response to OPTIONS:
>> HTTP/1.1 200 OK
>> Date: Wed, 14 Nov 2012 19:00:00 GMT
>> Server: Apache/2.5.x
>> X-Server-Load: 0.999
>> 
>> …the balancer might decide to use a backend that is reporting a lower load.
> 
> I know I am fighting the tide here, but it's really the wrong smarts to put in the load
balancer.
> 
> The backend should/can know if it can take more requests.  When it can't it shouldn't
and the load balancer shouldn't pass that back to the end-user but rather just find another
available server or hold on to the request until one becomes available (or some timeout value
is met if things are that bad).
> 

Without a doubt, I agree that the load info should not be passed
back to the end user (I state as much in the blog).


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