if obj.status == 50[1|2|3|x] -> reissue request on next backend(s)

[Gerald Leier]

hello again,

On Wed, 2009-09-02 at 11:15 -0300, Alexandre Haguiar wrote:
> This is my try...
> 
> If you dont need cache you can try pass to pipe mode in vcl_recv so
> all requests will be passed to backend and no 503 error will appear.
> 
> sub vcl_recv {
>        if (req.restarts > 0) {
>                set req.backend = test1;
>        } else {
>                set req.backend = test2;
>        }
> 
>        pipe;
> 
> Alexandre Haguiar
> 
thanks, but this doesnt work as i desire.


i reduced my config a bit more to match your codesniplet:
(removed director)
------------------
backend test1 {
        .host = "10.10.10.20";
        .port = "80";
}

backend test2 {
        .host = "10.10.10.30";
        .port = "80";
}

sub vcl_recv {
      if (req.restarts > 0) {
               set req.backend = test2;
       } else {
               set req.backend = test1;
       }
       pipe;
}

sub vcl_fetch {
    if (obj.status == 500 || obj.status == 501 || obj.status == 502 ||
obj.status == 503 || obj.status == 504) {
            restart;
    }
}

sub vcl_deliver {
        deliver;
}

--------

setup: test1 returns HTTP/1.1 500 Internal Server Error
       test2 returns HTTP/1.1 200 OK

now with the above config varnish does
give the request to test1 -> return the 500 error to client :(

thats not what i want :(

please tell me if i am trying to use varnish for something it isnt 
intended to be used for.

by now i think i may be playing with the wrong tool.

thanks for any hint

gerald










> 
> On Tue, Sep 1, 2009 at 12:15 PM, Gerald Leier <gerald.leier at lixto.com>
> wrote:
>         Hello again,
>         
>         thanks for the fast answer!
>         
>         unfortunatly i am still stuck.
>         
>         On Tue, 2009-09-01 at 09:48 +0000, Poul-Henning Kamp wrote:
>         > In message <1251797169.13050.48.camel at pioneer>, Gerald Leier
>         writes:
>         > >hello again,
>         > >
>         > >Is or isnt it possible to make varnish ask another backend
>         > >if the first returns a HTTP 500 or any other user defined
>         > >HTTP code when forwarding a users request?
>         > >
>         > >and if its possible -> whats the varnish way to do that?
>         >
>         > Use the "restart" facility, which basically tried the
>         request
>         > once more from the beginning, with any possible
>         modifications
>         > you have made or will make.
>         >
>         > Typically, you would set another backend in vcl_recv{},
>         > something like:
>         >
>         >       ...
>         >       if (req.restarts > 0) {
>         >               set req.backend = better_one;
>         >       } else {
>         >               set req.backend = normal_one
>         >       }
>         >
>         
>         
>         my setup consists of 3 machines.
>          1 loadbalancer
>          2 webservers(applicationservers)
>         
>         varnish version used:
>          varnishd (varnish-2.0.4)
>         
>         
>         i really do want to test nothing more then:
>          have two content servers.
>          round robin select one of them.
>          if the selected returns a 50x -> forward request to other
>         node
>          i dont need cashing, i dont need funny rewriting,
>          i dont need to embed fancy C code into VCL.
>          nothing like that.
>         
>          i even checked out and compiled the latest varnish because i
>         thought:
>         http://varnish.projects.linpro.no/changeset/3948
>          (have been rolling back to 2.0.4 since then for "my" vcl code
>         and the
>          2.1...varnish made it even worse)
>         
>         i dont want to post my whole config again. last time i did
>         that
>         no one seemed to think its worth answering such "massiv
>         amounts"
>         of spam.
>         (Subject: cant get restart; to fetch and deliver from other
>         backend on
>         HTTP error)
>         
>         
>         so here i am, with snipplets
>         .........
>         backend test1 {
>                .host = "10.10.10.20";
>                .port = "80";
>         }
>         
>         backend mars1 {
>                .host = "10.10.10.30";
>                .port = "80";
>         }
>         .........
>         
>         .........
>         sub vcl_recv {
>                if (req.restarts > 0) {
>                        set req.backend = test1;
>                } else {
>                        set req.backend = test2;
>                }
>         .........
>         
>         .........
>         sub vcl_fetch {
>            if (obj.status == 500 || obj.status == 503 || obj.status ==
>         504) {
>                    restart;
>            }
>         .........
>         
>         => 503 guru meditation.
>         
>         any hints, links or examples are very welcome.
>         
>         i dont like to give up on something i spent a few days on by
>         now...
>         at least not now. that of course may change if i dont get this
>         baby
>         up and running within another few days.
>         
>         lg
>          gerald
>         
>         
>         >
>         --
>         
>         
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>         varnish-misc at projects.linpro.no
>         http://projects.linpro.no/mailman/listinfo/varnish-misc
>         
> 
> 
> 
> -- 
> Alexandre Haguiar
--