Softpurge and nearly immediate refresh?

[Guillaume Quintard]

Hi,

You can purge then set the method to GET then restart. Would that work for
you?

Other way is to use req.hash_always_miss that will only revalidate if we
are able to fetch a new object.

-- 
Guillaume Quintard

On Sat, Apr 7, 2018 at 12:10 PM, Danila Vershinin <ciapnz at gmail.com> wrote:

> Hi,
>
> What I work with:
>
> * Grace mode configured to be 60 seconds when backend is healthy
> * Using softpurge module to adjust TTL to 0 upon PURGE.
>
> The whole idea is increasing chances that visitors will get cached page
> after cache was PURGEd for a page.
>
> Standard piece:
>
> sub vcl_hit {
>     if (obj.ttl >= 0s) {
>         # normal hit
>         return (deliver);
>     }
>
>     if (std.healthy(req.backend_hint)) {
>         # Backend is healthy. Limit age to 60s.
>         if (obj.ttl + 60s > 0s) {
>             set req.http.grace = "normal(limited)";
>             return (deliver);
>         } else {
>             return(fetch);
>         }
>     } else {
>         # ...
>     }
> }
>
> And use of softpurge:
>
> sub vcl_miss {
>     if (req.method == "PURGE") {
>         softpurge.softpurge();
>         return (synth(200, "Successful softpurge"));
>     }
> }
>
> sub vcl_hit {
>     if (req.method == "PURGE") {
>         softpurge.softpurge();
>         return (synth(200, "Successful softpurge"));
>     }
> }
>
>
>
> Current behaviour:
>
> * send PURGE for cached page
> * Visitor goes to the page within 60 seconds and sees a stale cached page
> (triggering background refresh)
> * Further visits to the page will show refreshed page
>
> What I’m looking for:
>
> Trigger the background refresh right after PURGE while still leveraging
> grace mode :) That is, serve stale cache for only as long as it takes to
> actually generate the new page, and not wait for 60 seconds:
>
> * upon PURGE: set TTL to 0 (softpurge) + trigger background page request
> (possible?)
> * serve stale cache only while the page is generated
>
> I could have adjusted the “healthy backend grace period” to lower than
> 60s, but I’m basically checking to see if it’s possible to refresh “nearly”
> immediately in this kind of setup.
>
> Hope I made any sense :)
>
> Best Regards,
> Danila
>
>
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