Varnish still 503ing after adding grace to VCL

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you need to enable a probe in the backend for this to work i believe.



On Mon, Mar 7, 2011 at 3:58 PM, Drew Smathers <drew.smathers at gmail.com>wrote:

> Hi all,
>
> I'm trying to grace as a means of ensuring that cached content is
> delivered from varnish past it's TTL if backends can't generate a
> response. With some experiments this does not seem to happen with our
> setup. After an object is cached, varnish still returns a 503 within
> the grace period if a backend goes down. Below are details.
>
> version: varnish-2.1.4 SVN 5447M
>
> I stripped down my VCL to the following to demonstrate:
>
> backend webapp {
>    .host = "127.0.0.1";
>    .port = "8000";
> }
>
> sub vcl_recv {
>   set req.backend = webapp;
>   set req.grace = 1h;
> }
>
>
> sub vcl_fetch {
>   set beresp.grace = 24h;
> }
>
> Running varnish:
>
> varnishd -f simple.vcl -s malloc,1G -T 127.0.0.1:2000 -a 0.0.0.0:8080
>
>
> First request:
>
> GET /some/path/ HTTP/1.1
> Accept-Language: en
>
> HTTP/1.1 200 OK
> Server: WSGIServer/0.1 Python/2.6.6
> Vary: Authorization, Accept-Language, X-Gttv-Apikey
> Etag: "e9c12380818a05ed40ae7df4dad67751"
> Content-Type: application/json; charset=utf-8
> Content-Language: en
> Cache-Control: max-age=30
> Content-Length: 425
> Date: Mon, 07 Mar 2011 16:12:56 GMT
> X-Varnish: 377135316 377135314
> Age: 6
> Via: 1.1 varnish
> Connection: close
>
>
> Wait 30 seconds, kill backend app, then make another request through
> varnish:
>
> GET /some/path/ HTTP/1.1
> Accept-Language: en
>
> HTTP/1.1 503 Service Unavailable
> Server: Varnish
> Retry-After: 0
> Content-Type: text/html; charset=utf-8
> Content-Length: 418
> Date: Mon, 07 Mar 2011 16:14:02 GMT
> X-Varnish: 377135317
> Age: 0
> Via: 1.1 varnish
> Connection: close
>
> Any help or clarification on request grace would be appreciated.
>
> Thanks,
> -Drew
>
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>
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