Stale While Revalidate Expires

[Rafael Cirolini]

Hi Maxim,


Thank so much for your response. You are correct, and the configuration of  proxy_cache_use_stale updating was present.


Stale while revalidate is a great option, and we use in a websites with more than 50 millions users/month.


This graph is our time to waiting to delivery pages to our users. We implement stale while revalidate in the beginning of Mai and we had an improvement of 30%.


[cid:179acb8c-85a4-4e56-ad12-b4953a6475bd]



Abraço,

Rafael Cirolini

Sup Programmatic & Digital Services

Terra Global

________________________________
De: nginx <nginx-bounces at nginx.org> em nome de Maxim Dounin <mdounin at mdounin.ru>
Enviado: quarta-feira, 7 de junho de 2017 11:26:45
Para: nginx at nginx.org
Assunto: Re: Stale While Revalidate Expires

Hello!

On Tue, Jun 06, 2017 at 07:33:24PM +0000, Rafael Cirolini wrote:

> We've just updated to 1.12 to use the stale-while-revalidate option.
>
> The application is who sends the cache-control header, like this:
> cache-control:max-age=180, stale-while-revalidate=60, stale-if-error=864000
>
> If I understood how SWR works, the user shouldn't receive stale content after 180+60 seconds.
>
> But we are seing stale content after this time.
> X-Cache-Status: STALE
>
> Our DevOps team did a debug:
> 2017/05/22 15:14:31 [debug] 21376#21376: *44 http file cache expired: 4 1495476646 1495476871
> 2017/05/22 15:14:31 [debug] 21376#21376: *44 http upstream cache: 4
> 2017/05/22 15:14:31 [debug] 21376#21376: *44 http file cache send: /var/cache/nginx/d/d2/fb19e1c85db7bda5c92ce21530bf5d2d
> 2017/05/22 15:14:31 [debug] 21376#21376: *44 http ims:1491861925 lm:1491861925
> 2017/05/22 15:14:31 [debug] 21376#21376: *44 http script var: "STALE"
>
> The correct answer should be EXPIRED after the max-age+SWR time.
>
> It looks reasonble to you?

The behaviour depends on whether you use "proxy_cache_use_stale
updating" in your configuration or not:

- If it is explicitly configured, it takes precedence over
  "Cache-Control: stale-while-revalidate=", and nginx will use any
  stale response available.

- If not configured, nginx will follow "stale-while-revalidate="
  specified in the response.

The debug log provided suggests that the configuration uses
"proxy_cache_use_stale updating" and
"proxy_cache_background_update on".

--
Maxim Dounin
http://nginx.org/
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