Pfthb

Well,I wanna make my website always online.

One method:Is it possible to cache a whole website using nginx proxy_pass for a login time?and how?
Actually i mean if the backend is down or not working,we can still use the cache for people to visit my website.

Another one method:crawler?

OR snapshot tech like search engin cached?

It is not actually possible for proxy_pass to cache websites (unless you have an actual application that has a cache of the website on the other end) as all it does is pass requests to another endpoint. Crawlers usually refer to search engine bots that look through a website for links so they can index all information on the website for the search engine hosting the crawler.

"Snapshots tech" works and are usually created by CDNs such as Cloudflare/Akamai, and is probably what you are looking for. CDNs are also used for many other things but I assume you are most interested in being able to show a copy of your website if it occasionally goes offline.

There is also another option that is setting browser caching headers in NGINX, that instructs the user's browsers to show a cached copy of your website and not update it until the cache expires. However, the downside is that your users will not be able to see the live copy of your website even if your website is online and that they would have to have visited your web page within the cache time to have cached it.

An example:

location ~* .(?:js|css|html)$ 
 expires 1d; #users' browsers cache it for a day
 add_header Pragma public;
 add_header Cache-Control "public";