Micro-caching is a technique used in Nginx web server to cache dynamic content for a very short period, typically in the order of milliseconds. It helps improve the performance and scalability of dynamic websites by reducing the load on the backend servers.
Caching Configuration:
To enable micro-caching in Nginx, you need to configure the caching directives in the Nginx server block. This includes specifying the cache zone and defining the cache duration.
http {
# Define the cache zone and its properties
proxy_cache_path /path/to/cache levels=1:2 keys_zone=my_cache:10m max_size=10g inactive=60m;
server {
# ...
location / {
# Enable caching for dynamic content
proxy_cache my_cache;
proxy_cache_valid 200 301 302 10s; # Cache responses with 200, 301, 302 status codes for 10 seconds
proxy_cache_use_stale error timeout updating http_500 http_502 http_503 http_504;
proxy_ignore_headers Cache-Control Expires;
proxy_cache_lock on;
proxy_cache_lock_age 5s;
proxy_cache_lock_timeout 5s;
# ...
}
}
}
In the configuration above, proxy_cache_path defines the storage location and properties of the cache. The proxy_cache directive enables caching for dynamic content in the specified cache zone (my_cache). The proxy_cache_valid directive specifies the cache validity duration for different response status codes.
Other directives like proxy_cache_use_stale, proxy_ignore_headers, proxy_cache_lock, etc., help handle edge cases and control caching behavior.
Caching Workflow:
When a client sends a request to the Nginx server, the server checks if the requested content is already present in the cache.
If it is, Nginx serves the cached content directly to the client without involving the backend server. If the content is not present in the cache or has expired, Nginx forwards the request to the backend server, receives the response, and caches it for subsequent requests.
Cache Invalidation:
Micro-caching operates on a very short cache duration, so cache invalidation is done automatically after the cache duration expires.
This ensures that dynamic content is not served stale for an extended period. When the cache expires, subsequent requests for the same content will trigger a fresh request to the backend server, and the response will be cached again.
Benefits and Considerations:
- Performance: Micro-caching reduces the load on backend servers by serving cached dynamic content. This leads to improved response times and better overall performance.
- Scalability: Caching dynamic content allows the backend servers to handle more concurrent requests since they don't need to generate the same content repeatedly.
- Cache Consistency: With micro-caching, there might be a slight delay in serving the most up-to-date content. If your website requires real-time data updates, micro-caching may not be suitable.
- Granularity and Usage: Micro-caching is typically applied to dynamic content that doesn't change frequently within a short timeframe. It's often used for content like product listings, comments, user profiles, etc., where a slightly stale version is acceptable for a short duration.
It's important to carefully evaluate your application's requirements and test the caching behavior thoroughly to ensure that micro-caching doesn't introduce unexpected issues or display stale content to users.