upstream: ip_hash and backup

[John Moore]

On 30/06/11 19:49, Maxim Dounin wrote:
> Hello!
>
> On Thu, Jun 30, 2011 at 07:35:24PM +0100, John Moore wrote:
>
>    
>> I'm using the upstream module to load balance between 2 back-end
>> servers, using ip_hash to effect a kind of 'stickiness' (making it
>> more likely that subsequent requests from the same client will go to
>> the same back-end server). Now I want to add a 3rd back-end server
>> into the mix, but which will only come into play if the other 2 are
>> failing. There's a handy 'backup' parameter I can use for this,
>> except that according to the docs it cannot be combined with the
>> ip_hash directive. I'm wondering whether there is some other way to
>> achieve what I want here? Effectively, the ip_hash becomes
>> irrelevant once it's failed over to this backup server as there is
>> only one.
>>      
> Use error_page based fallback instead, i.e. something like this:
>
>      upstream backends {
>          ip_hash;
>          server 10.0.0.1;
>          server 10.0.0.2;
>      }
>
>      upstream backup {
>          server 10.0.0.3;
>      }
>
>      server {
>          ...
>
>          location / {
>              error_page 502 504 = @fallback;
>              proxy_pass http://backends;
>          }
>
>          location @fallback {
>              proxy_pass http://backup;
>          }
>      }
>
>
>    
That's just what I need, thanks. Is this dependent on some recent 
version of nginx? I'm running 0.7.65.

John