Two sites with two different log files - SSL Apache2 Ubuntu - apache

Question

I have two websites in the same web server (Ubuntu 16.04.2 LTS - Apache/2.4.18). Everything works well when I try to access to both websites using HTTP (port 80). This is the vhosts.conf file content:
<VirtualHost *:80>
ServerName site1
DocumentRoot /var/www/html/site1
ErrorLog ${APACHE_LOG_DIR}/site1_error.log
CustomLog ${APACHE_LOG_DIR}/site1_access.log combined
</VirtualHost>
<VirtualHost *:80>
ServerName site2
DocumentRoot /var/www/html/site2
ErrorLog ${APACHE_LOG_DIR}/site2_error.log
CustomLog ${APACHE_LOG_DIR}/site2_access.log combined
</VirtualHost>
So, both sites are accessible through "mydomain.com/site1" and "mydomain.com/site2". I have installed a Let's Encrypt certificate and, to make it works, I have configured a virtual host like this:
<IfModule mod_ssl.c>
<VirtualHost *:443>
ServerName mydomain.com
DocumentRoot /var/www/html
ErrorLog ${APACHE_LOG_DIR}/site_error.log
CustomLog ${APACHE_LOG_DIR}/site_access.log combined
SSLCertificateFile /etc/letsencrypt/live/mydomain.com/fullchain.pem
SSLCertificateKeyFile /etc/letsencrypt/live/mydomain.com/privkey.pem
Include /etc/letsencrypt/options-ssl-apache.conf
</VirtualHost>
</IfModule>
I can access both site using SSL (port 443) successfully but I can't use different log files for different sites. I have tried something like this:
<IfModule mod_ssl.c>
<VirtualHost *:443>
ServerName mydomain.com/site1
DocumentRoot /var/www/html/site1
ErrorLog ${APACHE_LOG_DIR}/site1_error.log
CustomLog ${APACHE_LOG_DIR}/site1_access.log combined
Alias /site1 /var/www/html/site1
SSLCertificateFile /etc/letsencrypt/live/mydomain.com/fullchain.pem
SSLCertificateKeyFile /etc/letsencrypt/live/mydomain.com/privkey.pem
Include /etc/letsencrypt/options-ssl-apache.conf
</VirtualHost>
<VirtualHost *:443>
ServerName mydomain.com/site2
DocumentRoot /var/www/html/site2
ErrorLog ${APACHE_LOG_DIR}/site2_error.log
CustomLog ${APACHE_LOG_DIR}/site2_access.log combined
Alias /site2 /var/www/html/site2
SSLCertificateFile /etc/letsencrypt/live/mydomain.com/fullchain.pem
SSLCertificateKeyFile /etc/letsencrypt/live/mydomain.com/privkey.pem
Include /etc/letsencrypt/options-ssl-apache.conf
</VirtualHost>
</IfModule>
But it doesn't work. How can I distinguish between two sites in order to have two different log files?

Answer 1

Following the link proposed by CBroe, I have found the solution by using the SetEnvIf directive. The final working virtual host configuration looks like this:
<IfModule mod_ssl.c>
<VirtualHost *:443>
ServerName mydomain.com
DocumentRoot /var/www/html
SetEnvIf Request_URI ^/site1(/|$) site1
SetEnvIf Request_URI ^/site2(/|$) site2
CustomLog ${APACHE_LOG_DIR}/site1_access.log combined env=site1
CustomLog ${APACHE_LOG_DIR}/site2_access.log combined env=site2
ErrorLog ${APACHE_LOG_DIR}/site_error.log
SSLCertificateFile /etc/letsencrypt/live/mydomain.com/fullchain.pem
SSLCertificateKeyFile /etc/letsencrypt/live/mydomain.com/privkey.pem
Include /etc/letsencrypt/options-ssl-apache.conf
</VirtualHost>
</IfModule>