Varnish load balancer & (keep session)

[Rob S]

Just to copy in the list... the problem Axel was seeing is one that 
troubled us for a bit - getting unexpected 503 responses.

Solution: Make sure the top of "sub vcl_recv" has a default backend:

set req.backend = xxx;

You can override this later with conditional statements, or whatever, 
but having a default helps prevent 503s.


Rob


Axel DEAU wrote:
> Hi,
>
> It seems that with this method it works very well I thanks you a lot for your help and wich you have a nice day
>
> Best regard
>
> Axel DEAU | NOVACTIVE SYTEME
>
> Administrateur Systeme et Reseaux
> mail : a.deau at novactive-systemes.com
> Tel : + 33 1 48 24 33 60
> Fax : + 33 1 48 24 33 54
> www.novactive.com
>
>
> -----Message d'origine-----
> De : Rob S [mailto:rtshilston at gmail.com] 
> Envoyé : lundi 8 février 2010 11:50
> À : Axel DEAU
> Cc : Sacha MILADINOVIC
> Objet : Re: Varnish load balancer & (keep session)
>
> At the very top of "sub vcl_recv", please add:
>
> set req.backend = b1;
>
> This will set the default backend.
>
> Can you also send me the output of
>
> # varnishlog |grep Backend_health
>     0 Backend_health - server7 Still healthy 4--X-S-RH 10 8 10 0.007498 
> 0.009539 HTTP/1.1 200 OK
>     0 Backend_health - server2 Still healthy 4--X-S-RH 10 8 10 0.006767 
> 0.013814 HTTP/1.1 200 OK
>     0 Backend_health - server3 Still healthy 4--X-S-RH 10 8 10 0.012027 
> 0.010841 HTTP/1.1 200 OK
>
> from before and after you stop apache on the first and second backends.
>
>
> Rob
>
>
> Axel DEAU wrote:
>   
>> Hi,
>>
>> Absolutely
>>
>> Axel DEAU | NOVACTIVE SYTEME
>>
>> Administrateur Systeme et Reseaux
>> mail : a.deau at novactive-systemes.com
>> Tel : + 33 1 48 24 33 60
>> Fax : + 33 1 48 24 33 54
>> www.novactive.com
>>
>>
>> -----Message d'origine-----
>> De : Rob S [mailto:rtshilston at gmail.com] 
>> Envoyé : lundi 8 février 2010 10:24
>> À : Axel DEAU
>> Cc : Sacha MILADINOVIC
>> Objet : Re: Varnish load balancer & (keep session)
>>
>> Axel,
>>
>> Can you post your entire VCL, and I'll see why this is happening.
>>
>> Rob
>>
>> Axel DEAU wrote:
>>   
>>     
>>> Hi Rob,
>>>
>>> Thanks for the reply, for 1) when I shut down the second backend all the traffic goes to the first backend but,
>>> When I shut down the first backend even if the second backend mark "Still healthy" the error 503 appears.
>>>
>>> For the other point I'm agreed with you...
>>>
>>> -----Message d'origine-----
>>> De : Rob S [mailto:rtshilston at gmail.com] 
>>> Envoyé : dimanche 7 février 2010 13:33
>>> À : Axel DEAU
>>> Cc : varnish-misc at projects.linpro.no
>>> Objet : Re: Varnish load balancer & (keep session)
>>>
>>> Hi,
>>>
>>> To answer some of your questions:
>>>
>>> 1) 503 error when shutting down a backend:  When you shutdown the 
>>> backend, do you see varnishlog say that the backend is healthy or sick?  
>>> If one is sick, then the other should get the traffic if your VCL 
>>> contains set req.backend = b1;
>>>
>>> 2) Vanish load balanced does not keep e-commerce sessions for PHP.  The 
>>> simplest solution to this is to install memcache, and put the following 
>>> lines in your php.ini file:
>>>
>>> [Session]
>>> session.save_handler = memcached
>>> session.save_path = "memcache-server1:11211,memcache-server2:11211"
>>>
>>> instead of session.save_handler = files
>>>
>>> However, I can't say for certain that this will definitely work - it 
>>> depends on how your ecommerce application operates.
>>>
>>> 3) S-flag: I'm not sure about this, but my gut feeling is that it's not 
>>> causing the problems you're seeing.
>>>
>>>
>>>
>>> Rob
>>>
>>>
>>> Axel DEAU wrote:
>>>   
>>>     
>>>       
>>>> Version: 2.0.6-1
>>>>
>>>> Insall: .deb
>>>>
>>>> Os: Debian 5.0.3
>>>>
>>>> Hi,
>>>>
>>>> I've got two backends running apache2: front1.domain.com & 
>>>> front2.domain.com, set with the load balancing configuration 
>>>> from http://varnish-cache.org/wiki/LoadBalancing.
>>>>
>>>> _The issue is, when I shutdown apache2 of the first backend varnish 
>>>> don't switch to the second and display "Error 503 Service 
>>>> Unavailable", is that a normal answer from varnish?_
>>>>
>>>> Other question, _does varnish load balancer keep php sessions, if yes 
>>>> how will I do?_
>>>>
>>>> Varnishlog :
>>>>
>>>> 0 Backend_health - front1 Still healthy 4--X-RH 10 8 10 0.040008 
>>>> 0.039814 HTTP/1.1 200 OK
>>>>
>>>> 0 Backend_health - front2 Still healthy 4--X-RH 10 8 10 0.066948 
>>>> 0.066591 HTTP/1.1 200 OK
>>>>
>>>> The S flag is missing in my log, is that an issue…
>>>>
>>>> "4--X-S-RH" to notify that TCP socket shutdown succeeded 
>>>> from http://varnish-cache.org/wiki/BackendPolling
>>>>
>>>> Part of default.vcl
>>>>
>>>> backend front1 {
>>>>
>>>>   .host = "front1.domain.com";
>>>>
>>>>   .port = "80";
>>>>
>>>>   .probe = { .url = "/";
>>>>
>>>>              .interval = 10s;
>>>>
>>>>              .timeout = 5s;
>>>>
>>>>              .window = 10;
>>>>
>>>>              .threshold = 8;
>>>>
>>>>  }
>>>>
>>>> }
>>>>
>>>>  
>>>>
>>>> backend front2 {
>>>>
>>>>   .host = "front2.domain.com";
>>>>
>>>>   .port = "80";
>>>>
>>>>   .probe = { .url = "/";
>>>>
>>>>              .interval = 10s;
>>>>
>>>>              .timeout = 5s;
>>>>
>>>>              .window = 10;
>>>>
>>>>              .threshold = 8;
>>>>
>>>>  }
>>>>
>>>> }
>>>>
>>>>  
>>>>
>>>> director b1 random
>>>>
>>>> {
>>>>
>>>>    { .backend = front1; .weight = 5; }
>>>>
>>>>    { .backend = front2; .weight = 1; }
>>>>
>>>> }
>>>>
>>>>  
>>>>
>>>> #director b1 round-robin {
>>>>
>>>> #    { .backend = front1; }
>>>>
>>>> #    { .backend = front2; }
>>>>
>>>> #}
>>>>
>>>> Thanks for your help...
>>>>
>>>> ------------------------------------------------------------------------
>>>>
>>>> _______________________________________________
>>>> varnish-misc mailing list
>>>> varnish-misc at projects.linpro.no
>>>> http://projects.linpro.no/mailman/listinfo/varnish-misc
>>>>   
>>>>     
>>>>       
>>>>         
>>>   
>>>     
>>>       
>>   
>>     
>
>