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Apache2

Apache2 is an open-source web server that allows hosting websites and applications with support for modules, reverse proxy, and load balancing.

Apache2 Configuration​

The primary configuration file is /etc/apache2/apache2.conf. It controls global settings:

/etc/apache2/apache2.conf
# Global Configuration
Timeout 300
KeepAlive On
MaxKeepAliveRequests 100
KeepAliveTimeout 5

# Process Control
<IfModule mpm_prefork_module>
    StartServers 5
    MinSpareServers 5
    MaxSpareServers 10
    MaxRequestWorkers 150
    MaxConnectionsPerChild 3000
</IfModule>

# Enable required modules
LoadModule proxy_module modules/mod_proxy.so
LoadModule proxy_http_module modules/mod_proxy_http.so
LoadModule rewrite_module modules/mod_rewrite.so

Custom configurations are typically placed in /etc/apache2/sites-available/ and enabled with a2ensite, you have a full customizable service layer that you can configure, below is some way you can configure apache2

Serving Static Files​

To serve simple static files from Apache, configure a virtual host file like below

/etc/apache2/sites-available/static-site.conf
<VirtualHost *:80>
    ServerName static.example.com
    DocumentRoot /var/www/static

    <Directory /var/www/static>
        Options Indexes FollowSymLinks
        AllowOverride None
        Require all granted
    </Directory>

    ErrorLog ${APACHE_LOG_DIR}/error.log
    CustomLog ${APACHE_LOG_DIR}/access.log combined
</VirtualHost>

Enable config file and restart the apache server:

sudo a2ensite static-site.conf
sudo systemctl restart apache2

Reverse Proxy with Load Balancing​

configure Apache2 as a reverse proxy with load balancing, just create a new virtual host file like below

/etc/apache2/sites-available/reverse-proxy.conf
<VirtualHost *:80>
    ServerName example.com
    ProxyPreserveHost On
    ProxyPass / http://backend_cluster/
    ProxyPassReverse / http://backend_cluster/

    <Proxy balancer://backend_cluster>
        BalancerMember http://127.0.0.1:3000 loadfactor=1
        BalancerMember http://127.0.0.1:3001 loadfactor=2
        BalancerMember http://127.0.0.1:3002 loadfactor=1
    </Proxy>

    ErrorLog ${APACHE_LOG_DIR}/error.log
    CustomLog ${APACHE_LOG_DIR}/access.log combined
</VirtualHost>

Enable the configuration and restart Apache:

sudo a2ensite reverse-proxy.conf
sudo systemctl restart apache2

SSL Configuration​

To enable SSL, you simply just create an SSL-enabled virtual host file like below

/etc/apache2/sites-available/ssl-site.conf
<VirtualHost *:443>
    ServerName example.com
    SSLEngine on
    SSLCertificateFile /etc/apache2/ssl/example.com.crt
    SSLCertificateKeyFile /etc/apache2/ssl/example.com.key

    ProxyPass / http://127.0.0.1:3000/
    ProxyPassReverse / http://127.0.0.1:3000/

    ErrorLog ${APACHE_LOG_DIR}/error.log
    CustomLog ${APACHE_LOG_DIR}/access.log combined
</VirtualHost>

Enable the configuration and restart Apache:

sudo a2ensite ssl-site.conf
sudo systemctl restart apache2

Virtual Hosts for Multiple Websites​

To host multiple websites, just create separate virtual host files.

Example 1:

/etc/apache2/sites-available/example1.conf
<VirtualHost *:80>
    ServerName example1.com
    DocumentRoot /var/www/example1

    <Directory /var/www/example1>
        AllowOverride All
        Require all granted
    </Directory>
</VirtualHost>

Example 2:

/etc/apache2/sites-available/example2.conf
<VirtualHost *:80>
    ServerName example2.com
    DocumentRoot /var/www/example2

    <Directory /var/www/example2>
        AllowOverride All
        Require all granted
    </Directory>
</VirtualHost>

Like usual, enable the site and restart apache2

sudo a2ensite example1.conf example2.conf
sudo systemctl restart apache2

Enabling Required Modules​

To enable necessary modules, run:

sudo a2enmod proxy proxy_http ssl rewrite headers
sudo systemctl restart apache2