Varnish - set backend if statuscode is 404

[Per Buer]

On Fri, Nov 29, 2013 at 5:04 AM, Norberto Meijome <numard at gmail.com> wrote:

> +1, this is how we do this ( and similar tricks)
>
> @per, you suggested saint mode. Why? What would it do better than Tobias'
> solution?
>

Saint mode works if you have two backends in the same director. Then it
blacklists that object from that backend for a certain time. A restart
would then direct the request to the other backend.

Tobias solution is to have two backends. The other one is only used when
the first one fails.

Per.

> Thx,
> On 29/11/2013 3:10 AM, "Tobias Honacker" <t.honacker at googlemail.com>
> wrote:
>
>> Hi Jan,
>>
>> This is my solution:
>>
>> sub vcl_recv {
>>
>> // Redirect 404er Pictures - vcl_fetch will restart request and set new
>> header to match with this rule
>> if (req.http.host == "new-header.de") {
>>        if (req.url ~ "^/var/storage/images") {
>>            set req.backend = new_backend;
>>        }
>>         }
>> }
>>
>>
>> sub vcl_fetch {
>>
>>         if ((beresp.status == 404) && (req.url ~ "^/var/storage/images"))
>> {
>>      set req.http.Host = "new-header.de";
>>      return(restart);
>>         }
>> }
>>
>>
>> You have to set a new header and restart the request thats it.
>>
>>
>> Best regards,
>> Tobias
>>
>> Am 28.11.13 16:15 schrieb "Jan-Frode Myklebust" unter <janfrode at tanso.net
>> >:
>>
>> >If you manage to do this, I would much appreciate you post a recipie :-)
>> >I've been struggeling trying to achieve the same thing, without
>> >success..
>> >
>> >Actually my setup is a bit different, we have a director, and just want
>> >to check the other backend if the first backend gives 404, but the same
>> >solution might apply.
>> >
>> >backend backend1 {
>> >        .host = "backend1.example.com";
>> >        .probe = {
>> >                .url = "/alive.html";
>> >                .timeout = 34 ms;
>> >                .interval = 2s;
>> >                .window = 10;
>> >                .threshold = 8;
>> >        }
>> >}
>> >backend backend2 {
>> >        .host = "backend2.example.com";
>> >        .probe = {
>> >                .url = "/alive.html";
>> >                .timeout = 34 ms;
>> >                .interval = 2s;
>> >                .window = 10;
>> >                .threshold = 8;
>> >        }
>> >}
>> >director dir1 client {
>> >    { .backend = backend1; .weight = 1; }
>> >    { .backend = backend2; .weight = 1; }
>> >}
>> >sub vcl_recv {
>> >        if ( req.http.host ~ "(?i)www.example.com$"  ) {
>> >                set req.backend = dir1;
>> >                return(lookup);
>> >        }
>> >}
>> >
>> >
>> >
>> >  -jf
>>
>>
>>
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>
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-- 
 <http://www.varnish-software.com/> *Per Buer*
CTO | Varnish Software AS
Phone: +47 958 39 117 | Skype: per.buer
We Make Websites Fly!

Winner of the Red Herring Top 100 Europe Award 2013
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