Softpurge and nearly immediate refresh?

[Danila Vershinin]

Hi Guillaume,

A bit puzzled on something. If we use Vary: by some header.. am I correct that we need multiple restarts to refresh each object variation?

Since the background fetch would only refresh the variation that matched initial purge request. 

Sent from my iPhone

> On 9 Apr 2018, at 12:18, Guillaume Quintard <guillaume at varnish-software.com> wrote:
> 
> 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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> 
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