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From János Löbb <janos.l...@yale.edu>
Subject Re: JK 1.2.28 - load balancer worker fails on startup with one worker down ?
Date Mon, 20 Apr 2009 15:23:21 GMT

On Apr 17, 2009, at 8:28 AM, André Warnier wrote:

> Rainer Jung wrote:
> [...]
>> What remains for me is your suggestion, that the error is not a fatal
>> one, since there are other balanced workers left. We could include  
>> such
>> a check in the startup code, although I'm not really convinced, that
>> your problem is a good reason for this.
>> I'm open to more argumntation and suggestions :)
> Argumentation #1 against a change in logic:
> The OP argues that one single unresolvable balanced worker should  
> not stop the other 4 from working, hence that the balancer should  
> start anyway, since 80% of the capacity is still available.  It  
> sounds reasonable in principle.
> But what if there are only 2 balanced workers in total, of which one  
> is unresolvable at start ? would it be normal to start with only one  
> balanced worker available anyway ?
> If not, then where's the limit of "acceptable" ?
>
> Argumentation #2 against a change in logic:
> Suppose the balancer would start, with the resolved workers only.
> Suppose the resolving problem comes from a typo, not the fact that  
> the given host is temporarily out of the DNS system, but a definite  
> non-existing host.  It will not be retried, so there will never be  
> another error/warning message. The host itself may be ok and respond  
> to pings etc.., it will just never be hit by Apache's mod_jk, so  
> this would be a very quiet error.
> How is the sysadmin going to figure out that there is, basically, a  
> problem ?
>
> Argumentation for a change in logging:
> It would be clearer if the error message stated explicitly that "the  
> balancer worker was not started due to a /configuration/ error, see  
> above message(s)".
>
> But then, if even I could figure it out from the existing error  
> message, then just about everyone should be able to.
> And what would be the use of the likes of me, if everything was  
> clear ?
> ;-)
>

Perheps with a variable:

JkQuorum

This could be set between two and the number of workers under the  
command of the loadbalancer.  If it is not set, then old behavior can  
be followed, or be set internally to 2 or to the tomcat instances  
balanced.

János
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