How to Configure Nginx fastcgi_cache for WordPress Acceleration

Nginx fastcgi_cache for WordPress Acceleration

This tutorial explains how to configure Nginx's fastcgi_cache to accelerate HTML pseudo-static page delivery for WordPress sites, based on an LNMP environment.

Prerequisites

Ensure you have an LNMP stack (e.g., LNMP 1.4 or later) with at least:

• MySQL 5.5.56
• PHP 5.5.38
• TCmalloc

Install the ngx_cache_purge Module

First, check if the module is installed:

nginx -V 2>&1 | grep -o ngx_cache_purge

If no output, install it:

1. Navigate to the source directory:

   cd /usr/local/src

2. Download ngx_cache_purge:

   wget http://labs.frickle.com/files/ngx_cache_purge-2.3.tar.gz

3. Extract it:

   tar zxvf ngx_cache_purge-2.3.tar.gz

4. Download matching Nginx source (e.g., 1.12.0):

   wget http://nginx.org/download/nginx-1.12.0.tar.gz

5. Extract and enter:

   tar zxvf nginx-1.12.0.tar.gz
   cd nginx-1.12.0

6. Get current Nginx compile options:

   nginx -V

7. Reconfigure with the module added:

   ./configure [your existing options] --add-module=../ngx_cache_purge-2.3

8. Compile:

   make

9. Backup and replace the binary:

   mv /usr/local/nginx/sbin/nginx{,_$(date +%F)}
   cp objs/nginx /usr/local/nginx/sbin

10. Verify installation:

    nginx -V 2>&1 | grep -o ngx_cache_purge

Configure fastcgi_cache

Edit your site's Nginx configuration file (e.g., /usr/local/nginx/conf/vhost/www.example.com.conf). Before the server block, add:

fastcgi_cache_path /tmp/wpcache levels=1:2 keys_zone=WORDPRESS:250m inactive=1d max_size=1G;
fastcgi_temp_path /tmp/wpcache/temp;
fastcgi_cache_key "$scheme$request_method$host$request_uri";
fastcgi_cache_use_stale error timeout invalid_header http_500;
fastcgi_ignore_headers Cache-Control Expires Set-Cookie;

Inside the server block, update the PHP location block and add cache logic:

server {
    listen 80;
    server_name www.example.com;
    root /home/wwwroot/www.example.com;

    set $skip_cache 0;
    if ($request_method = POST) { set $skip_cache 1; }
    if ($query_string != "") { set $skip_cache 1; }
    if ($request_uri ~* "/wp-admin/|/xmlrpc.php|wp-.*.php|/feed/|index.php|sitemap(_index)?.xml|purge=all") { set $skip_cache 1; }
    if ($http_cookie ~* "comment_author|wordpress_[a-f0-9]+|wp-postpass|wordpress_no_cache|wordpress_logged_in") { set $skip_cache 1; }

    location ~ [^/].php(/|$) {
        try_files $uri =404;
        fastcgi_pass unix:/tmp/php-cgi.sock;
        include fastcgi.conf;
        fastcgi_cache_bypass $skip_cache;
        fastcgi_no_cache $skip_cache;
        add_header X-Cache "$upstream_cache_status From $host";
        fastcgi_cache WORDPRESS;
        fastcgi_cache_valid 200 301 302 1d;
    }

    location / {
        try_files $uri $uri/ /index.php?$args;
    }

    location ~ /purge(/.*) {
        allow 127.0.0.1;
        allow YOUR_SERVER_IP;
        deny all;
        fastcgi_cache_purge WORDPRESS "$scheme$request_method$host$1";
    }

    location ~* ^.+.(ogg|ogv|svg|svgz|eot|otf|woff|mp4|ttf|rss|atom|jpg|jpeg|gif|png|ico|zip|tgz|gz|rar|bz2|doc|xls|exe|ppt|tar|mid|midi|wav|bmp|rtf)$ {
        expires max;
        access_log off;
        log_not_found off;
    }
}

server {
    server_name example.com;
    return 301 $scheme://www.example.com$request_uri;
}

Save and restart Nginx: lnmp restart.

WordPress Configuration

Install the Nginx Helper plugin. In wp-config.php, add:

define('RT_WP_NGINX_HELPER_CACHE_PATH', '/tmp/wpcache');

In the plugin settings, set "Purge Method" to "Delete local server cache files".

Alternative: Code-Based Cache Purging

Add this to your theme's functions.php for automatic cache purging without a plugin:

// Configuration
$logSwitch = 0;
$logFile = '/tmp/purge.log';
$cache_path = '/tmp/wpcache';

// Manual purge for admins: ?purge=all
if (isset($_GET['purge']) && $_GET['purge'] == 'all' && is_user_logged_in() && current_user_can('manage_options')) {
    delDirAndFile($cache_path, 0);
}

// Hook into publishing and comments
add_action('publish_post', 'Clean_By_Publish', 99);
add_action('comment_post', 'Clean_By_Comments', 99);
add_action('comment_unapproved_to_approved', 'Clean_By_Approved', 99);

function Clean_By_Publish($post_ID) {
    $url = get_permalink($post_ID);
    cleanFastCGIcache($url);
    cleanFastCGIcache(home_url() . '/');
    // Optional: clean category and tag pages
    if ($categories = wp_get_post_categories($post_ID)) {
        foreach ($categories as $cat_id) cleanFastCGIcache(get_category_link($cat_id));
    }
    if ($tags = get_the_tags($post_ID)) {
        foreach ($tags as $tag) cleanFastCGIcache(get_tag_link($tag->term_id));
    }
}

function Clean_By_Comments($comment_id) {
    $comment = get_comment($comment_id);
    cleanFastCGIcache(get_permalink($comment->comment_post_ID));
}

function Clean_By_Approved($comment) {
    cleanFastCGIcache(get_permalink($comment->comment_post_ID));
}

function cleanFastCGIcache($url) {
    global $cache_path;
    $url_data = parse_url($url);
    if (!$url_data) return;
    $hash = md5($url_data['scheme'] . 'GET' . $url_data['host'] . $url_data['path']);
    $cache_path = rtrim($cache_path, '/') . '/';
    $cached_file = $cache_path . substr($hash, -1) . '/' . substr($hash, -3, 2) . '/' . $hash;
    if (file_exists($cached_file)) unlink($cached_file);
}

function delDirAndFile($path, $delDir = FALSE) {
    $handle = opendir($path);
    if ($handle) {
        while (false !== ($item = readdir($handle))) {
            if ($item != "." && $item != "..") {
                is_dir("$path/$item") ? delDirAndFile("$path/$item", $delDir) : unlink("$path/$item");
            }
        }
        closedir($handle);
        if ($delDir) return rmdir($path);
    } else {
        if (file_exists($path)) return unlink($path);
    }
}

Note: Ensure purge=all is in your Nginx skip-cache rules to prevent the purge URL itself from being cached.

Additional Performance Tips

• Memcached: Use for object caching. Install via ./addons.sh install memcached and place the appropriate object-cache.php in wp-content.
• OPcache: Accelerates PHP execution. Enable via ./addons.sh install opcache if not already active.

After configuration, check the X-Cache header in your browser's developer tools. A value of HIT indicates the cache is working.