1. Apache

Apache allows configuring the number of concurrent connections through its modules and directives in the main configuration file, usually located at /etc/apache2/apache2.conf or /etc/httpd/httpd.conf, depending on the operating system.

Key parameters:

• MaxRequestWorkers: Defines the maximum number of simultaneous requests that Apache can handle.
  <IfModule mpm_prefork_module>
MaxRequestWorkers 150
</IfModule>

• ServerLimit: Defines the maximum number of processes Apache can spawn.
  <IfModule mpm_worker_module>
ServerLimit 256
</IfModule>

• MaxConnectionsPerChild: Defines the maximum number of connections each child process handles before being recycled.
  MaxConnectionsPerChild 1000


After making these changes, restart Apache with:

2. Nginx

In Nginx, the configuration of simultaneous connections is mainly controlled through the following parameters in the configuration file located at /etc/nginx/nginx.conf:

Key parameters:

• worker_processes: Defines the number of worker processes Nginx will run. This should align with the number of CPU cores on the server.
  worker_processes auto;

• worker_connections: Defines the maximum number of simultaneous connections that a single worker process can handle.
  worker_connections 1024;

• events: This section allows configuring event handling parameters, such as the I/O method used.
  events {
worker_connections 1024;
}


The total number of simultaneous connections Nginx can handle is the product of worker_processes and worker_connections.

Once the changes are made, restart Nginx with:

3. PHP-FPM

If your web application uses PHP-FPM to handle PHP requests, you should configure the number of concurrent connections in the php-fpm.conf file or in the pool files, located in /etc/php/7.4/fpm/pool.d/www.conf (the path may vary depending on the PHP version).

Key parameters:

• pm.max_children: Sets the maximum number of PHP-FPM processes that can run simultaneously.
  pm.max_children = 50

• pm.start_servers: The number of processes that start when the service begins.
  pm.start_servers = 5

• pm.max_spare_servers: The maximum number of spare (idle) processes.
  pm.max_spare_servers = 10


After making changes, restart PHP-FPM:

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