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

  • 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)

– KS
Web Developer at Benedictine University near Chicago