Avoiding "Zend_Db_Adapter_Exception"

[LFrank2021]

With the installation of icinga-director 1.11.5-1 and icinga-director-daemon 1.11.5-1 I often saw the following error message after a system reboot

# systemctl status icinga-director.service
...
Zend_Db_Adapter_Exception in /usr/share/icinga-php/vendor/vendor/shardj/zf1-future/library/Zend/Db/Adapter/Pdo/Abstract.php:173 with message: SQLSTATE[HY000] [2002] No such file or directory
 <- PDOException in /usr/share/icinga-php/vendor/vendor/shardj/zf1-future/library/Zend/Db/Adapter/Pdo/Abstract.php:143 with message: SQLSTATE[HY000] [2002] No such file or directory

This was happening even after explicitly setting pdo_mysql.default_socket and mysqli.default_socket in apache2's php.ini.

Could this be an issue with apache2 and/or icingadb not being ready yet?
After adding After=apache2.service icingadb.service to the service file the issue has not been seen yet.

Best regards
Frank