What role combinations are allowed?

An instance must have at least one role in Scalarium. Multiple roles are allowed, but not all role combinations are allowed.

You can for example have a Rails application server instances that is the MySQL database server at the same time. But being a load balancer and a Web server is not possible.

This is due to the installed software by each role, both HAProxy (load balancer) and Nginx (Web server) bind to port 80, so a setup would not succeed. So Scalarium only allows valid combinations. Your custom roles can mix and match with every other role.

Please not an already running instance cannot acquire more roles. Only non-running instances can be added to an existing role.

You can only remove a role from an instance if it is not running.