How to configure Nginx to handle PHP-FPM connection pooling and reuse?

To configure Nginx to handle PHP-FPM connection pooling and reuse, you need to make the following changes to the Nginx configuration file:

Open the Nginx configuration file using a text editor. This file is usually located at /etc/nginx/nginx.conf or /etc/nginx/conf.d/default.conf.
Inside the http block, add or modify the upstream directive to define the PHP-FPM connection pool. For example:

http {
    ...
    upstream php_fpm {
        server unix:/var/run/php/php7.4-fpm.sock;
        server unix:/var/run/php/php7.3-fpm.sock;
        server unix:/var/run/php/php7.2-fpm.sock;
        ...
    }
    ...
}

In this example, three PHP-FPM sockets are defined as part of the connection pool. You can add or remove sockets as per your PHP-FPM setup.

Inside the server block where the PHP-FPM requests will be processed, configure the location block to route the requests to the PHP-FPM connection pool. For example:

server {
    ...
    location ~ \.php$ {
        fastcgi_pass php_fpm;
        fastcgi_param SCRIPT_FILENAME $document_root$fastcgi_script_name;
        include fastcgi_params;
    }
    ...
}

Here, the fastcgi_pass directive is set to the named upstream php_fpm, which is the connection pool defined earlier.

Save the changes to the configuration file and exit the text editor.
Test the Nginx configuration for any syntax errors:

sudo nginx -t

If there are no errors, proceed to the next step. Otherwise, correct the errors and then test again.

Finally, reload the Nginx configuration to apply the changes:

sudo systemctl reload nginx

With these configurations, Nginx will route PHP requests to the available PHP-FPM sockets in a round-robin fashion, effectively managing connection pooling and reuse.