mod_proxy_balancer / failover (hot standby)

[an...@gzs.de]

Hello,

I´d like to restart the thread
http://www.gossamer-threads.com/lists/apache/dev/305214

Summary of that thread:
Ruediger Plum fixed mod_proxy_balancer so that the status=d became persistent.
(http://svn.apache.org/viewcvs?rev=374929&view=rev)

Having applied the fix / using the following config..:

 ProxyPass / balancer://mycluster stickysession=SESSION_COOKIE
  <Proxy balancer://mycluster> 
	BalancerMember http://192.168.4.2:80 route=a redirect=b 
	BalancerMember http://192.168.4.3:80 route=b status=d 
  </Proxy>

..the behaviour is the following (a little too persistent perhaps ;):

After shutting down Member a, it gets status err, but member b stays disabled -> Apache returns error 503.
I now have to remove the "status=d" for member b myself.

The expected behaviour would have been: member b gets the requests as soon as member a is in error state.

The thread (see link above) ended with Ruediger Plums questions and answers from Robby Pedrica:
> 
> 1. What is the exact meaning of a disabled worker? Should it be considered 
> for use if find_best_worker cannot find a worker in non error mode and nofailover 
> is set to off? 
> Should a redirected worker that is disabled be used? 

I´d say yes.
Robby suggested a new type of status "stdby" to differenciate between standby and disabled. Sounds also good if people need that.

> 2. What about chains of redirects (worker 'a' has a redirect to worker 'b', 
> worker 'b' has a redirect to worker 'c')? 
Considering hotstandby/failover only, I am not seeing a need to care about this. Looks like a different issue to me.


Please let me know if I just missed a correct config - otherwise I am curious to hear what you think and if you perhaps can provide another fix...?

Thanks and best regards,
Andreas

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Re: mod_proxy_balancer / failover (hot standby)

[Ruediger Pluem <rp...@apache.org>]

On 02/28/2006 05:46 PM, andreas.wieczorek@gzs.de wrote:
> Hello,
> 
> I´d like to restart the thread
> http://www.gossamer-threads.com/lists/apache/dev/305214

Thanks for starting this again. I also lost track of it.


> 
> Please let me know if I just missed a correct config - otherwise I am curious to hear what you think and if you perhaps can provide another fix...?

No you did not miss the correct config. Currently it does not work without the patch attached somewhere in

http://www.gossamer-threads.com/lists/apache/dev/305214

One further obstacle is that it seems to me that even with the patch it does not do a failover if you do
not already have a session. So some broader changes are actually needed.

I hope (and hoped) to get some feedback by other developers on this issue to clarify the definition of 'disabled'.
Once this is done we can go into the details about how to implement this.


Regards

Rüdiger