document docker deployment and management

[alee]

Need docs for both prod and dev deployments.

Upgrading containers

• http://stackoverflow.com/questions/26734402/how-to-upgrade-docker-container-after-its-image-changed
• how to handle app updates and django DB migrations?

[warmdev]

I think this involves:

• Requirements
  • Strict separation of apps and data as suggested in the link (which we have been doing)
  • Separate the miracle app itself and the deployment scripts (Dockerfiles and scripts) into separate repositories. This is not necessary but cleaner in my opinion. Then the miracle Dockerfile pulls the miracle app from its GitHub repo.
  • The startup script (CMD) in the miracle Dockerfile would perform migrations and static file collections (something like https://github.com/warmdev/miracle-docker/blob/master/miracle.sh but can be more complex as required)
• Update procedure
  • Update Dockerfiles (for example to use newer versions of Java or DeployR)
  • Prepare databases (sometimes newer versions of apps may require the databases be upgraded using special scripts or instructions)
  • Force rebuild all images (there is no such command available at the moment I think. What we can do is to simply add or remove a space from the first line of a Dockerfile which will force it to rebuild)
  • Take down the website, stop the containers, and start the containers using new images in the right order

[warmdev]

Update: It is possible to force rebuild an image without cache using the --no-cahe=true flag. However this will rebuild the entire image from start. If we only want to rebuild from a certain line, use the blank space method as mentioned above.