I'd respectfully like to submit my project, Convox, into the discussion of not reinventing a PaaS:

http://convox.com/

https://github.com/convox/rack

Convox is another open source PaaS, but we're building it entirely on top of AWS services like CloudFormation, ECS, ASG, etc.

This means it's only suitable for teams that have 100% bought into AWS. If that's you, we make all the hard parts of operating a distributed deployment system Amazon's problem.

There's another project in this same space, Empire: https://github.com/remind101/empire

If 100% AWS is not you, Docker Datacenter / Swarm, CoreOS, Deis, CloudFoundry, etc. are doing incredible work.

It's amazing how these sophisticated tools are available to all of us.