There is a simple static web page with some images, located under www directory. Images could be shuffled on the filesystem with /scripts/shuffle.sh script.
The web page and images are served by Nginx web server. The configuration file is located under config/nginx.conf.
Nginx runs two services: one on port 8081, which doesn't use cache and always loads files from a filesystem. The second one runs on 8080 and performs caching, using the first service as a backend.
The cache bypasses two first requests of an image. Individual image cache can be forced to reload by adding a X-Update-Cache header to a request.
- Run
docker-compose upto start Nginx. - Open http://localhost:8080 in your browser.
- Notice that images match their descriptions.
- Reload page two times and check the logs/cache.log file. You should see that the first two requests are not cached, subsequent requests are cached.
- Run
./scripts/shuffle.shto shuffle images on the filesystem. Reload page and notice that images are cached and not updated. - Run
./refresh.shspecifying set of images like100 101 102 200 201 202 300 301 302 400 401 402 500 501 502to force cache reload for them. Reload page and notice that images are updated now.
The caching behavior is controlled by the following configuration directives:
Using cache for each url:
proxy_cache_path /var/cache/nginx levels=1:2 keys_zone=img_cache:100m inactive=60m;
proxy_cache_key "$scheme$request_method$host$request_uri";
Bypassing cache for the first two requests:
proxy_cache_min_uses 2;
Forcing cache reload:
proxy_cache_bypass $http_x_update_cache;