使Nginx缓存尊重缓存控制标头

Question

Nginx can cache content, ie act as a reverse-proxy, but the purge time must be fixed in the Nginx config.

Is there a way to make Nginx purge automatically according to cache-control headers from upstream app servers?

Answer 1

After researching this issue, I found it's not well documented as most people seem concerned with CMSs where it's easy to say "cache articles for a day", but less so for dynamic app servers which may vary according to each request.

Several options are:

• Nginx Plus
• Ngx Cache Purge module , though it hasn't seen any updates in 2 years
• Define multiple caches with different expiry times and apply them differently by path, if that's possible.
• Forget caching on Nginx and put a server like Varnish in front of it.

Update: Looking further, I now think proxy_cache_valid doesn't even need to be present. It just sets a default expiry if there's no cache-control/expiry from upstream. Nginx will still consider content as stale if there's no proxy_cache_valid, but it won't immediately be purged. The reason it keeps stale content in the cache (determined with "inactive" param and optionally proxy_cache_valid) is that it can serve stale content using proxy_cache_use_stale (useful if there's an error upstream).