[gedrap]

Sounds like a fun project (and totally doable)! :)

If I were you, I'd make heavy use of ansible, or something similar, for provisioning:

1) folks are familiar with it 2) could make it cross-platform more easily 3) well, no reinventing the wheel.

For example, Ansible has ec2 module http://docs.ansible.com/ansible/ec2_module.html where you describe an instance and the number of them that should be running. So if you have 3 instances running and wish to have 5, it does the magic and spins up new ones. Then, you can add them to a load balancer. Maybe there's something similar for DO already?

The way I see it is that it would poll if scaling conditions are met and execute ansible playbooks if they are, and then some web interface to set the conditions / view the scaling logs / current status.

It can turn out to be a very entertaining and educational side project :)

If you decide to do it, drop me an email - something I would be happy to brainstorm and discuss about :)

EDIT: It could also be used not only for autoscaling but also for self-healing. If some instance crashed and is not responding anymore, then spin up a new one.

[vidarh]

I've build setups like this with Ansible, but the more I use Ansible, the less likely it is that I'll consider it for future projects. I find it a lot less painful to write code to do these things directly than wrestle with Ansible. E.g. the amount of pain I went through before realising that the EC2 module at the time messed with whitespace in the user-data (great when you're transferring yaml... one more reason I detest significant whitespace; but the irony of this breaking in a tool written in Python was not lost on us), for example.

[gedrap]

I guess it depends on the use case. If all you want to do is to make sure that, for example, all web servers have the same version of nginx, php and sync the configs of these services, I think ansible is a great tool and writing code to do that would definitely qualify as 'reinventing the wheel'.

I wouldn't disqualify the tool for a problem in one of the modules either. Bugs happen :)