How Nginx implements cache control configuration for HTTP requests

How Nginx implements cache control configuration for HTTP requests

As a high-performance web server and reverse proxy server, Nginx has powerful cache management and control functions , caching control of HTTP requests can be achieved through configuration. This article will introduce in detail how Nginx implements cache control configuration for HTTP requests and provide specific code examples.

1. Overview of Nginx cache configuration
Nginx cache configuration is mainly implemented through the proxy_cache module. This module provides a wealth of instructions and parameters that can effectively control cache behavior. Before configuring the cache, you need to load the proxy_cache module in the Nginx configuration file. The specific instruction is:

load_module modules/ngx_http_proxy_module.so;

This instruction will load the Nginx proxy_cache module so that we can use relevant cache control in the configuration file. instruction.

2. Detailed explanation of cache control instructions

1. proxy_cache_path

The proxy_cache_path instruction is used to define the cache path and related configuration parameters, such as cache storage path, cache size, caching strategy, etc. The specific usage is as follows:

proxy_cache_path /data/nginx/cache levels=1:2 keys_zone=my_cache:10m max_size=10g
               inactive=60m use_temp_path=off;

In this example, we define a cache area named my_cache, the cache path is /data/nginx/cache, the maximum cache size is 10GB, and the cache expiration time is 60 minutes. . It should be noted that the configuration parameters need to be adjusted according to actual needs.

2. proxy_cache

The proxy_cache directive is used to enable caching and set the cache area used. It can be configured in the location block, for example:

location / {
    proxy_cache my_cache;
    proxy_cache_valid 200 304 5m;
    proxy_cache_valid 301 302 1h;
    proxy_cache_key $host$uri$is_args$args;
    proxy_cache_use_stale error timeout updating http_500 http_502 http_503 http_504;
    proxy_cache_background_update on;
    proxy_cache_lock on;
    proxy_cache_lock_timeout 5s;
    proxy_cache_revalidate on;
    proxy_cache_min_uses 3;
    proxy_cache_bypass $http_x_token;
    proxy_cache_methods GET HEAD;
}

In the above configuration, we enabled the cache area named my_cache and set the cache validity time, cache key, cache update strategy and other parameters for different response status codes. These parameters can be flexibly configured according to specific caching requirements.

3. proxy_ignore_headers

The proxy_ignore_headers directive is used to specify the HTTP response headers that Nginx needs to ignore when caching, for example:

proxy_ignore_headers Cache-Control Set-Cookie;

In this example, We require Nginx to ignore the Cache-Control and Set-Cookie response headers when caching to ensure the consistency and effectiveness of the cache.

4. proxy_cache_lock

The proxy_cache_lock instruction is used to control concurrent access to cached content, which can effectively avoid cache breakdown, avalanche and other problems, for example:

proxy_cache_lock on;
proxy_cache_lock_timeout 5s;

In this example, we enable cache locking and set a 5-second timeout after which requests will continue to hit the backend server to update the cache content.

3. Code Example
Based on the above cache control instructions, we can write a complete Nginx configuration example to implement cache control of HTTP requests. The following is a simple Nginx configuration example:

load_module modules/ngx_http_proxy_module.so;

http {
    proxy_cache_path /data/nginx/cache levels=1:2 keys_zone=my_cache:10m max_size=10g
               inactive=60m use_temp_path=off;

    server {
        listen 80;
        server_name example.com;

        location / {
            proxy_pass http://backend_server;
            proxy_cache my_cache;
            proxy_cache_valid 200 304 5m;
            proxy_cache_valid 301 302 1h;
            proxy_cache_key $host$uri$is_args$args;
            proxy_cache_use_stale error timeout updating http_500 http_502 http_503 http_504;
            proxy_cache_background_update on;
            proxy_cache_lock on;
            proxy_cache_lock_timeout 5s;
            proxy_cache_revalidate on;
            proxy_cache_min_uses 3;
            proxy_cache_bypass $http_x_token;
            proxy_cache_methods GET HEAD;
            proxy_ignore_headers Cache-Control Set-Cookie;
        }
    }
}

In the above example, we first loaded the ngx_http_proxy_module module, then defined a cache area named my_cache, and configured a proxy location in the server block, and Caching and corresponding cache control directives are enabled. When a user accesses example.com, Nginx will perform cache management and control based on the configured cache rules.

4. Summary
Through the above introduction and examples, we have a detailed understanding of how Nginx implements the cache control configuration of HTTP requests, and a detailed explanation and demonstration of the relevant instructions provided by the proxy_cache module. Reasonable cache configuration can greatly improve the access speed and performance of the website, reduce the pressure on the back-end server, and achieve a better user experience. Therefore, in actual web application development, it is very important to use Nginx's cache control function appropriately.

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