Zero Downtime app deployment with CoreOS

Question

I have a docker container that I want to deploy to a CoreOS cluster that has to download my app from a git repo.

Let's say the app container runs nginx / nodejs

How should I update it?

If i submit the container and start it, that works the first time. But the second time I'll have to stop/start the container with fleetctl then I'll obviously have downtime. Should I start up new containers that are derived from that container?

Answer 1

Here's a complete walkthrough on exactly such a scenario:

http://coreos.com/blog/zero-downtime-frontend-deploys-vulcand.html

Answer 2

Instead of pulling down your application from github inside your container, you should bake your application code inside your container/image. Your container should start its services within a few seconds. To achieve zero downtime you should keep the old container running until your new container has started and is ready to accept new connections. You could do this by separating nginx into its own container and keep it running all the time.