Containerized Applications with Docker

An introduction to developing applications with Docker. Given at Ancient City Ruby 2015

1. Containerized Ruby Applications with Docker Laura Frank rheinwein @rhein_wein
3. +
4. Containerization: What even is it? How do I use Docker within my applications? How can I use Docker with Ruby? Three Questions
6. Docker may seem trendy right now… but there’s a reason it’s popular.
7. Docker != containers
8. A tool for managing containers • Executing and running code • Managing code Docker
9. First, let’s talk about containers.
10. • Run in a self-contained execution environment • Share the kernel of host system • Are isolated from other containers • Have fast boot times & low overhead Containers
11. LXC/libcontainer/… - container format namespaces - isolation cgroups - sharing unionfs - layering Containers
12. A container is a virtualization layer — sort of like a VM — but with some fundamental differences Containers can work in conjunction with or in place of virtual machines (VMs).
13. hardware host OS hypervisor $ guest OS libraries web $ guest OS $ guest OS libraries DB libraries web
14. hardware host OS libraries web libraries DB libraries web
15. hardware host OS container runtime engine libraries libraries web web DB
16. Containers have slightly more complexity but They reduce the amount of time/space resources needed to run your application
18. A tool for managing containers • Executing and running code • Managing code Docker
19. Engine Hub docker.com
20. The Docker Hub • Ideas • News • Images (Docker Registry)
21. registry.hub.docker.com
22. Using Ruby with Docker
23. Installing Docker
24. Anything else? You need to use a lightweight VM. Pro Tip: Boot2Docker (OSX and Windows) Installing Docker Linux? Install Docker with official packages. Kitematic (OSX)
25. CLI REST API docs.docker.com Interacting with Docker
27. Docker Images An image is controlled by a Dockerfile docker build -t foo/bar . docker pull foo/bar
28. • Static: all files and code are contained in image • Dynamic: link folders to actively modify code (development only) Sehr wichtig/very important/¡muy importante! Docker Images
29. FROM centurylink/ruby-base:2.1.2 MAINTAINER Laura Frank <ljfrank@gmail.com> EXPOSE 4567 RUN mkdir -p /usr/src/app ADD . /usr/src/app WORKDIR /usr/src/app RUN bundle install CMD “ruby hello_world.rb" Dockerfile
30. FROM centurylink/ruby-base:2.1.2 MAINTAINER Laura Frank <ljfrank@gmail.com> EXPOSE 4567 RUN mkdir -p /usr/src/app ADD . /usr/src/app WORKDIR /usr/src/app RUN bundle install CMD “ruby hello_world.rb" Dockerfile
31. FROM centurylink/ruby-base:2.1.2 MAINTAINER Laura Frank <ljfrank@gmail.com> EXPOSE 4567 RUN mkdir -p /usr/src/app ADD . /usr/src/app WORKDIR /usr/src/app RUN bundle install CMD “ruby hello_world.rb" Dockerfile
32. FROM centurylink/ruby-base:2.1.2 MAINTAINER Laura Frank <ljfrank@gmail.com> EXPOSE 4567 RUN mkdir -p /usr/src/app ADD . /usr/src/app WORKDIR /usr/src/app RUN bundle install CMD “ruby hello_world.rb" Dockerfile
33. FROM centurylink/ruby-base:2.1.2 MAINTAINER Laura Frank <ljfrank@gmail.com> EXPOSE 4567 RUN mkdir -p /usr/src/app ADD . /usr/src/app WORKDIR /usr/src/app RUN bundle install CMD “ruby hello_world.rb" Dockerfile
34. FROM centurylink/ruby-base:2.1.2 MAINTAINER Laura Frank <ljfrank@gmail.com> EXPOSE 4567 RUN mkdir -p /usr/src/app ADD . /usr/src/app WORKDIR /usr/src/app RUN bundle install CMD “ruby hello_world.rb" Dockerfile
35. FROM centurylink/ruby-base:2.1.2 MAINTAINER Laura Frank <ljfrank@gmail.com> EXPOSE 4567 RUN mkdir -p /usr/src/app ADD . /usr/src/app WORKDIR /usr/src/app RUN bundle install CMD “ruby hello_world.rb" Dockerfile
36. ENV KEY value Declare any environment variables that will be passed to any RUN command. VOLUME /var/foo VOLUME [“/var/foo”, “/var/bar”] creates a mount point for volumes from host or other containers
37. FROM centurylink/ruby-base:2.1.2 Dockerfile No need for gemset or version management, just use a different base image. Base images are great!
38. Official Ruby Images https://registry.hub.docker.com/_/ruby/ Support for 1.9.3+ docker pull ruby:2.1.X Repository includes instructions for bootstrapping
39. Gems From Swipely: docker-api: for interacting with the Docker API from your Ruby application Over 30 other gems
40. (Sorry.) …is kind of a pain. Debugging in a Container…
41. Debugging in a Container Use Pry. require ‘pry’ class Thing def some_method binding.pry #some brilliant broken code end end
42. Debugging in a Container No need for a remote session* Alternatively, use pry command: docker run centurylink/panamax-api pry
44. Application Architecture with Docker
45. Simply put, Docker architecture is service-oriented architecture. If a service fails, new containers can be spun up in milliseconds.
46. DB Web One Service, One Container
47. Bind 8080:4567 Expose 3306 link One Service, One Container DB Web
48. Configuration can happen in two places: The Dockerfile, by baking config options into the service’s base image The docker run string, by specifying configuration options with various flags Configuring an Application
49. Bind 8080:4567 Expose 3306 One Service, One Container link DB Web
50. Bind 8080:4567 The Dockerfile Link: DB Web FROM centurylink/ruby-base:2.1.2 MAINTAINER Laura Frank <ljfrank@gmail.com> RUN mkdir -p /usr/src/app ADD . /usr/src/app WORKDIR /usr/src/app RUN bundle install CMD ["ruby", "hello_world.rb"]
51. Bind 8080:4567 FROM centurylink/ruby-base:2.1.2 MAINTAINER Laura Frank <ljfrank@gmail.com> ENV APIKEY=superSeCrEt01234567abcdef! RUN mkdir -p /usr/src/app ADD . /usr/src/app WORKDIR /usr/src/app RUN bundle install CMD ["ruby", "hello_world.rb"] The Dockerfile Link: DB Web
52. Bind 8080:4567 Link: DB The Docker Run String Web docker run -p 8080:4567 -e “APIKEY=superSeCrEt01234567abcdef!” —-link db:db my-image
53. The Docker Run String Each container has own docker run string Can only start one container at a time via CLI Multiple containers can run from the same image Find balance between docker run and Dockerfile
54. …that sounds like a lot of tedious work.
56. Application Templating Use your own images, or images from the Docker Registry Specify config options beforehand Run applications with one or two simple commands
57. Standards tightly coupled with Docker docs.docker.com/compose Dump requirements into docker-compose.yml and run with docker-compose up Docker Compose
58. Docker workflow tool Itself a containerized application panamax.io Uses CoreOS, Fleet, and etcd for orchestration and service discovery
59. Templating language similar to docker compose Supports remote deployments panamax.io/get-panamax
60. --- name: Rails with PostgreSQL description: Rails with PostgreSQL images: - category: Web Tier name: Rails source: rheinwein/rails:latest description: Rails App type: Default expose: [] ports: - host_port: '8080' container_port: '3000' links: - service: Database alias: DB_1 environment: [] volumes: []
61. Parting Thoughts Extract commonalities from images in order to share them Don’t include any user- or org-specific configurations in an image or application template Boot2Docker Use an application template
62. Additional Resources Docker Hub: registry.hub.docker.com Documentation: docs.docker.com Boot2Docker: boot2docker.io Panamax: panamax.io CenturyLink Labs: centurylinklabs.com
63. Thanks! Laura Frank rheinwein @rhein_wein