Cache a reverse proxy site

1 Why cache a reverse proxy site

Caching a reverse proxied site improves performance and the user experience, and also strengthens stability and security:

• Performance: resources enter the cache on the first request, so later requests are answered from cache with fewer backend round trips;
• Less backend load: cached images, CSS and JavaScript free the application server to handle dynamic requests;
• Bandwidth savings: repeated requests for the same resource are served by the proxy instead of the origin;
• Better experience: faster resource loading means smoother pages and shorter waits;
• Stability: cached and distributed requests mean one overloaded server no longer affects the whole system;
• Hot updates: cache lifetimes can be tuned per status so updated content reaches users quickly;
• Security: long lifetimes for immutable assets reduce direct exposure of the origin.

2 Configure proxy caching

Add proxy_cache to the location of a reverse proxied site:

{
  "listen": 9090,
  "server_name": "localhost",
  "location": [
    {
      "url": "/",
      "type": "proxy",
      "proxy_pass": "http://xxxx.com",
      "proxy_cache": {
        "path": "cache",
        "valid": ["200:1h", "304:1h", "any:30m"],
        "key": "$request_method$host$request_uri"
      }
    }
  ]
}

proxy_cache enables the proxy cache:

The example caches the upstream xxxx.com: path is the cache location, valid lists the lifetime for each status (status 200 is cached for one hour, any falls back to 30 minutes) and key builds the cache file name.

3 Recommendations

• Sites with many static assets benefit the most;
• For fast-changing APIs, shorten the lifetime of the matching status codes or exclude them from caching;
• RELOAD after changing proxy_cache.