These are notes from a talk by Laura Frank during the HighEdWeb 2015 Technology Academy. Laura works at CodeShip.

https://github.com/rheinwein/rails-demo-apps

• Docker != containers
• Docker is a tool that managers containers
  • Build images to run as containers
  • Responsible for code execution
  • Con manage entire applications with docker-compose
  • Provision machines with docker-machine
  • docker-swarm: management for many machines
• A Container is a virtualization layer - sort of like a VM - but with some fundamental differences.
• You can use Docker inside of other VMs
• Containers
  • Self-contained execution environment
  • Share the kernel of host system
  • Are isolated from other containers
  • Fast boot-times and low overhead
• This can seem complex, but they can greatly reduce the amount of time and space needed to run your application. When you close the container, everything is gone.
• TL;DR: spend less time fight with dependencies, more time building what you want.
• The Docker Ecosystem: Build, ship, run
• Docker Images: are images containers? No, an image is like a class and a container is an instance of that class
• The Docker Hub: repos of Docker Images, webhooks, build triggers, authentication, private repos. Web GUI or CLI
• Different Types of Images:
  • Service: self-contained service like PostgreSQL or MySQL
  • Project Base: intended to serve as a base of your own project. Does not directly provide a service, like Ruby, golang.
  • Official Image: maintained by the organization/company themselves (official Rails image)
• Build Your Own Docker Images
  • starts with a docker file
  • Docker Compose (yml)
  • Docker Toolbox
• How to get the containers to communicate with one another: linking, environmental variables, some additional configuration
• What about persistent data? Mounting directories/volumes; you can mount a special volume for databases.
• Race conditions? Docker service could be up and tunning, but the service itself might not actually be available yet. Custom script to do a health check to see if it is available
• Docker in Production
  • Integrating with CI/CD
  • Can run tests, build new images, pushing that image to a registry, firing up containers with the new image
  • Some kind of orchestration tool should be doing this for you. (Kubernetes)

Peace
– KS
Web Developer at Benedictine University near Chicago