Configuring resource limits in Apache virtual hosts involves setting directives that control the amount of server resources allocated to each virtual host. This can help prevent a single virtual host from consuming excessive resources and impacting the overall server performance. Below are the steps to configure resource limits in Apache virtual hosts:

Enable mod_cgid or mod_cgi:

Ensure that the mod_cgid or mod_cgi module is enabled in your Apache configuration. This module is responsible for executing CGI scripts and is required for setting resource limits.

• Use the following command to enable mod_cgid module:

   a2enmod cgid

• Or, you can use the following command to enable the mod_cgi module:

a2enmod cgi

After enabling the module, restart Apache:\

systemctl restart apache2 

Configure Resource Limits

Open the Apache configuration file for the specific virtual host you want to configure. This file is typically located in the /etc/apache2/sites-available/ directory.

<VirtualHost *:80>
    ServerName example.com
    DocumentRoot /var/www/html/example

    <Directory "/var/www/html/example">
        Options +ExecCGI
        AddHandler cgi-script .cgi

        LimitRequestBody 1048576
        Timeout 30
        MaxRequestWorkers 150
        MaxConnectionsPerChild 100
        RLimitCPU 10
        RLimitMEM 1048576
        RLimitNPROC 50
    </Directory>
</VirtualHost>

Here are some commonly used directives for resource limits, along with their explanations:

LimitRequestBody

This sets the limit on the size of the request body:

LimitRequestBody 1048576  # Limit request body to 1 MB

Timeout

This sets the maximum time, in seconds, that the server will wait for a request to complete:

Timeout 30  # Set the maximum request processing time to 30 seconds

MaxRequestWorkers

This sets the maximum number of simultaneous connections that will be processed:

MaxRequestWorkers 150  # Set the maximum number of simultaneous connections to 150

MaxConnectionsPerChild

This sets the maximum number of connections a child process will handle before it is terminated and replaced with a new one.

MaxConnectionsPerChild 100  # Set the maximum connections per child process to 100

RLimitCPU and RLimitMEM

This limits the CPU time and memory a process can consume:

RLimitCPU 10  # Limit CPU usage to 10 seconds
RLimitMEM 1048576  # Limit memory usage to 1 GB

RLimitNPROC

This limits the number of processes a user can create:

RLimitNPROC 50  # Limit the number of processes to 50

Restart Apache

After making changes to the Apache configuration, restart the Apache web server to apply the changes:

   systemctl restart apache2 

Verify that the virtual host is working correctly, and the resource limits are enforced.