Nothing should be deleting your /var/log/apache2/ directory and if it is, you need to do this and find out what's deleting it and report it:
mkdir -p /var/log/apache2
chown root:adm /var/log/apache2
chmod 750 /var/log/apache2
touch /var/log/apache2/.write-protect
chattr +i /var/log/apache2/.write-protect
this will prevent the directory from being recursively or forcefully deleted, and any attempt will result in: rm: cannot remove 'apache2/.write-protect': Operation not permitted because the .write-protect file has been made immutable and can't be deleted. Note: this will not prevent other files in the directory from being deleted, but rather just the .write-protect file itself and subsequently prevent the parent directory because directories can't be deleted unless they're empty. I really can't imagine what could possibly be deleting your logs directory, though and whatever it is needs to be corrected.
The only other explanation I can think of is that your /var/log or /var/log/apache2 directory is being mounted from tmpfs (as unlikely as it seems its not unimaginable but it would certainly be custom) in which case everything will always be ephemeral and you will need to modify your apache2 service unit to make sure the directory is created, you could do that like:
systemctl stop apache2
systemctl disable apache2
cp /usr/lib/systemd/system/apache2.service /etc/systemd/system/my-apache2.service
- edit the
/etc/systemd/system/my-apache2.service and add the following line under [Service]:
ExecStartPre=mkdir /var/log/apache2 && chown -R root:adm /var/log/apache2 && chmod 750 /var/log/apache2
save the contents then exit, and type systemctl daemon-reload
and type systemctl start my-apache2 and check that it starts OK with systemctl status my-apache2 if it does, systemctl enable my-apache2 to have it start at boot each time.
