How to Configure Nginx as a HTTP Cache

In the world of web servers, Nginx has emerged as a popular choice among the various server software available today. It’s known for its high performance, stability, rich feature set, simple configuration, and low resource consumption.

One of the powerful features of Nginx is its ability to act as a HTTP cache, which can significantly improve the performance of your website by reducing server load and improving response times.

This tutorial will guide you through the process of configuring Nginx as a HTTP cache, step by step.

Understanding HTTP Caching

Before we dive into the configuration process, it’s important to understand what HTTP caching is and why it’s beneficial.

Imagine you’re running a news website, and you have a popular article that’s being accessed by thousands of users every minute. Every time a user requests this article, your web server has to fetch the article from the database, process it, and then send it to the user. This involves a lot of work and can put a significant load on your server, especially if you’re getting a lot of traffic on a shared hosting account.

Now, let’s say you implement HTTP caching on your server. The first time a user requests the article, your server does the usual work of fetching the article from the database and processing it. But instead of just sending it to the user, it also stores a copy of the processed article in the cache.

The next time a user requests the same article, instead of fetching it from the database and processing it again, your server simply serves the copy that’s stored in the cache. This is much faster and puts less load on your server.

So, by using HTTP caching, you’re able to serve the same article to thousands of users more efficiently. This can significantly improve the performance of your website, especially if you’re using a dedicated server, VPS server, or cloud hosting solution, where resources like CPU and memory can be a limiting factor.

Prerequisites

Before you start, you’ll need the following:

• An installed and running instance of Nginx.
• Root or sudo access to your server.
• A basic understanding of Nginx configuration files and directives.

Step 1: Setting Up the Cache Path

The first step in configuring Nginx as a HTTP cache is to set up the cache path. This is where Nginx will store the cached data. You can do this by adding the following directive to your Nginx configuration file:

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

In this directive:

• /path/to/cache – This is the location where the cache files will be stored.
• levels=1:2 – This defines the hierarchy levels of the cache.
• keys_zone=my_cache:10m – This creates a shared memory zone called “my_cache” that will store the cache keys and metadata. The size is set to 10MB.
• max_size=1g – This sets the maximum size of the cache. In this case, it’s set to 1GB.
• inactive=60m – This sets the duration that a cache file is allowed to be inactive before it’s removed. In this case, it’s set to 60 minutes.
• use_temp_path=off – This disables the use of a temporary path for storing cache files while they’re being transferred.

Step 2: Configuring the Proxy Cache

The next step is to configure the proxy cache. This involves setting up the caching behavior for your website. This can be done by adding the following directives to your Nginx configuration file:

server {
    location / {
        proxy_cache my_cache;
        proxy_pass http://your_backend;
        proxy_cache_valid 200 302 60m;
        proxy_cache_valid 404 1m;
    }
}

In this configuration:

• proxy_cache my_cache; – This enables caching for this location block and specifies “my_cache” as the cache zone.
• proxy_pass http://your_backend; – This sets the backend server that Nginx will proxy requests to.
• proxy_cache_valid 200 302 60m; – This sets the duration that successful responses (HTTP 200 and 302) will be considered valid in the cache. In this case, it’s set to 60 minutes.
• proxy_cache_valid 404 1m; – This sets the duration that 404 responses will be considered valid in the cache. In this case, it’s set to 1 minute.

Step 3: Configuring Cache Bypass

Sometimes, you might want to bypass the cache under certain conditions. This can be achieved using the proxy_cache_bypass directive. For example, you can bypass the cache if a certain cookie is set:

server {
    location / {
        proxy_cache my_cache;
        proxy_pass http://your_backend;
        proxy_cache_bypass $cookie_nocache;
    }
}

In this configuration, if the “nocache” cookie is set, Nginx will bypass the cache and fetch the response from the backend server.

Step 4: Configuring Stale Content Delivery

Nginx can be configured to serve stale content from its cache when it can’t get fresh content from the origin servers. This can be useful in situations where all the origin servers for a cached resource are down or temporarily busy. To enable this functionality, include the proxy_cache_use_stale directive:

server {
    location / {
        proxy_cache my_cache;
        proxy_pass http://your_backend;
        proxy_cache_use_stale error timeout http_500 http_502 http_503 http_504;
    }
}

With this configuration, if Nginx receives an error, timeout, or any of the specified 5xx errors from the origin server and it has a stale version of the requested file in its cache, it delivers the stale file instead of relaying the error to the client.

Commands Mentioned

• proxy_cache_path – Sets the path and configuration of the cache.
• proxy_cache – Enables caching for a location block and specifies the cache zone.
• proxy_pass – Sets the backend server that Nginx will proxy requests to.
• proxy_cache_valid – Sets the duration that certain responses will be considered valid in the cache.
• proxy_cache_bypass – Bypasses the cache under certain conditions.
• proxy_cache_use_stale – Serves stale content from the cache when it can’t get fresh content from the origin servers.

FAQ

1. What is the benefit of configuring Nginx as a HTTP cache?

   Configuring Nginx as a HTTP cache can significantly improve the performance of your website by reducing the load on your server and improving response times. It does this by storing HTTP responses and serving them for subsequent requests, reducing the need for repeated data fetching and processing.

2. What does the proxy_cache_path directive do?

   The proxy_cache_path directive sets the path and configuration of the cache in Nginx. It specifies where the cache files will be stored, the hierarchy levels of the cache, the shared memory zone for cache keys and metadata, the maximum size of the cache, the inactive duration of cache files, and whether to use a temporary path for storing cache files while they’re being transferred.

3. How can I bypass the cache in Nginx?

   You can bypass the cache in Nginx using the proxy_cache_bypass directive. This directive allows you to specify conditions under which the cache should be bypassed. For example, you can bypass the cache if a certain cookie is set.

4. What does the proxy_cache_use_stale directive do?

   The proxy_cache_use_stale directive allows Nginx to serve stale content from its cache when it can’t get fresh content from the origin servers. This can be useful in situations where all the origin servers for a cached resource are down or temporarily busy. Instead of relaying the error to the client, Nginx delivers the stale version of the file from its cache.

5. Can Nginx cache dynamic content?

   Yes, Nginx can cache dynamic content, provided the Cache-Control header allows for it. Caching dynamic content for even a short period of time can reduce load on origin servers and databases, which improves time to first byte, as the page does not have to be regenerated for each request.

Conclusion

Configuring Nginx as a HTTP cache is a powerful way to improve the performance of your website. By storing HTTP responses and serving them for subsequent requests, you can reduce server load and improve response times.

This tutorial has guided you through the process of setting up the cache path, configuring the proxy cache, setting up cache bypass conditions, and configuring the delivery of stale content.

Remember to always test your configuration changes before applying them to your live server to ensure everything works as expected.

Happy hosting!