Nginx – serving stale cache response while updating

cachenginx

In nginx I am using the

proxy_cache_use_stale updating

directive (http://nginx.org/en/docs/http/ngx_http_proxy_module.html#proxy_cache_use_stale) so that concurrent request to an invalidated cached content only send 1 request to the upstream (the non-first request respond with stale content while the first request is updating the content).

this works well.

Now is there a way to also have the first request respond immediately with stale content, while at the same time triggering the update ?

right now, the response time is very good for non-first invalidating request, but the first one needs to wait until the backend responds. I would prefer serving stale content until the cache is updated.

Best Answer

What you're looking for is called stale-while-revalidate (RFC 5861) and it's implemented in nginx as a directive called proxy_cache_background_update. Similar functionality can be found in Varnish 4 and in Squid this is called Collapsed Forwarding.

Correct way in new versions of nginx

Turn out my first answer to this question was correct at certain time, but it turned into another pitfall - to stay up to date please check Taxing rewrite pitfalls

I have been corrected by many SE users, so the credit goes to them, but more importantly, here is the correct code:

server {
       listen         80;
       server_name    my.domain.com;
       return         301 https://$server_name$request_uri;
}

server {
       listen         443 ssl;
       server_name    my.domain.com;
       # add Strict-Transport-Security to prevent man in the middle attacks
       add_header Strict-Transport-Security "max-age=31536000" always; 

       [....]
}

Nginx – How to alter the Last-Modified header on nginx

"I want the content I'm serving not to be cached" : You can turn off If-Modified-Since request header checking with if_modified_since off; directive. if_modified_since doc

And about Last-Modified header: You can turn it off with add_header Last-Modified "";

Best Answer

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NGINX Redirect – How to Rewrite All HTTP Requests to HTTPS While Maintaining Sub-Domain

Correct way in new versions of nginx

Nginx – How to alter the Last-Modified header on nginx

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