Containerizing Rails: Techniques, Pitfalls, & Best Practices

Presentation by Daniel Azuma at RailsConf 2018. Covers best practices for designing Docker images for Rails applications. More information at http://daniel-azuma.com/railsconf2018

Transcript

2. Containerizing Rails Techniques, Pitfalls, & Best Practices Daniel Azuma Google Cloud Platform
3. Daniel Azuma http://daniel-azuma.com/ @danielazuma
5. Languages, Optimizations, and Libraries
6. Languages, Optimizations, and Libraries
8. Basic concepts
9. Håkan Dahlström, "Multicolored Containers" Source: https://www.flickr.com/photos/dahlstroms/3144199355 License: https://creativecommons.org/licenses/by/2.0/
10. Isolation
12. • File system
13. • File system • CPU allocation
14. • File system • CPU allocation • Memory
15. • File system • CPU allocation • Memory • Network stack
16. • File system • CPU allocation • Memory • Network stack • Users
17. • File system • CPU allocation • Memory • Network stack • Users • Processes
18. • File system • CPU allocation • Memory • Network stack • Users • Processes
19. • File system • CPU allocation • Memory • Network stack • Users • Processes != VM
20. • File system • CPU allocation • Memory • Network stack • Users • Processes Linux host
21. • File system • CPU allocation • Memory • Network stack • Users • Processes CPU arch Linux kernel Linux host:
22. • File system • CPU alloc • Memory • Network stack • Users • Processes CPU arch Linux kernel Linux host: • File system • CPU alloc • Memory • Network stack • Users • Processes • File system • CPU alloc • Memory • Network stack • Users • Processes
23. Images
25. Dockerfile
26. # Rails Dockerfile FROM ruby WORKDIR /opt/app COPY . /opt/app RUN bundle install ENV PORT=8080 CMD ["bundle", "exec", "rails", "server"]
27. # Rails Dockerfile FROM ruby WORKDIR /opt/app COPY . /opt/app RUN bundle install ENV PORT=8080 CMD ["bundle", "exec", "rails", "server"]
28. # Rails Dockerfile FROM ruby WORKDIR /opt/app COPY . /opt/app RUN bundle install ENV PORT=8080 CMD ["bundle", "exec", "rails", "server"]
29. # Rails Dockerfile FROM ruby WORKDIR /opt/app COPY . /opt/app RUN bundle install ENV PORT=8080 CMD ["bundle", "exec", "rails", "server"]
30. # Rails Dockerfile FROM ruby WORKDIR /opt/app COPY . /opt/app RUN bundle install ENV PORT=8080 CMD ["bundle", "exec", "rails", "server"]
31. # Rails Dockerfile FROM ruby WORKDIR /opt/app COPY . /opt/app RUN bundle install ENV PORT=8080 CMD ["bundle", "exec", "rails", "server"]
32. Which base image?
33. FROM ruby FROM alpine FROM phusion/baseimage ??? Tip #1: Read and understand your base image
34. Size does matter
35. apt-get install
36. RUN apt-get clean \ && rm -f /var/lib/apt/lists/*_*
37. RUN apt-get update -y RUN apt-get install -y -q mypackage RUN apt-get clean \ && rm -f /var/lib/apt/lists/*_*
38. RUN apt-get update -y \ && apt-get install -y -q mypackage \ && apt-get clean \ && rm -f /var/lib/apt/lists/*_*
39. FROM base-image
40. FROM base-image RUN apt-get update
41. FROM base-image RUN apt-get update RUN apt-get install mypkg
42. FROM base-image RUN apt-get update RUN apt-get install mypkg RUN apt-get clean
43. FROM base-image RUN apt-get update \ && apt-get install mypkg \ && apt-get clean Tip #2: Combine install commands with cleanup
44. RUN apt-get install build-essential \ && bundle install
45. http://artgallery.msfc.nasa.gov/4459.html Source: NASA
46. FROM my-base AS builder COPY . /app RUN apt-get install build-essential \ && bundle install --deployment FROM my-base COPY --from=builder /app /app
47. FROM my-base AS builder COPY . /app RUN apt-get install build-essential \ && bundle install --deployment FROM my-base COPY --from=builder /app /app
48. FROM my-base AS builder COPY . /app RUN apt-get install build-essential \ && bundle install --deployment FROM my-base COPY --from=builder /app /app Ruby base image
49. FROM my-base AS builder COPY . /app RUN apt-get install build-essential \ && bundle install --deployment FROM my-base COPY --from=builder /app /app Ruby base image App source
50. FROM my-base AS builder COPY . /app RUN apt-get install build-essential \ && bundle install --deployment FROM my-base COPY --from=builder /app /app Ruby base image App source Compilers, etc.
51. FROM my-base AS builder COPY . /app RUN apt-get install build-essential \ && bundle install --deployment FROM my-base COPY --from=builder /app /app Ruby base image App source Vendored gems Compilers, etc.
52. FROM my-base AS builder COPY . /app RUN apt-get install build-essential \ && bundle install --deployment FROM my-base COPY --from=builder /app /app Ruby base image Ruby base image App source Vendored gems Compilers, etc.
53. FROM my-base AS builder COPY . /app RUN apt-get install build-essential \ && bundle install --deployment FROM my-base COPY --from=builder /app /app Ruby base image Ruby base image App source Vendored gems Compilers, etc. App w/vendored gems
54. FROM my-base AS builder COPY . /app RUN apt-get install build-essential \ && bundle install --deployment FROM my-base COPY --from=builder /app /app Ruby base image Ruby base image App source Vendored gems Compilers, etc. App w/vendored gems
55. FROM my-base AS builder COPY . /app RUN apt-get install build-essential \ && bundle install --deployment FROM my-base COPY --from=builder /app /app Ruby base image App w/vendored gems Tip #3: Use a separate build stage
56. Gerd Rohs, "Image in the image" https://pixabay.com/en/image-in-the-image-mobile-phone-2204798/ CC0
58. RUN echo "en_US.UTF-8 UTF-8" > /etc/locale.gen \ && locale-gen en_US.UTF-8 ENV LANG en_US.UTF-8 ENV LANGUAGE en_US:en Tip #4: Set the system locale
59. "Australia in a Nutshell" (Sign contents modified) Photo by: Kristian Thøgersen Source: https://www.flickr.com/photos/flottenheimer/5534636006 License: https://creativecommons.org/licenses/by/2.0/
60. Tip #5: Create an unprivileged user # After building your app... RUN adduser -s /bin/sh -u 1001 -G root \ -h /app -S -D rails \ && chown -R rails /app USER rails
61. # Exec form CMD ["bundle", "exec", "rails", "s"] # Shell form CMD bundle exec rails s
62. # Exec form CMD ["bundle", "exec", "rails", "s"] # Shell form CMD bundle exec rails s Tip #6: Prefer exec form for CMD
63. # Exec form CMD ["bundle", "exec", "rails", "s"] # Shell form CMD exec bundle exec rails s Tip #7: Prefix shell form with the “exec” keyword
64. ONBUILD
65. # Base image... ONBUILD COPY . /app ONBUILD RUN bundle install # ...
66. # Base image... ONBUILD COPY . /app ONBUILD RUN bundle install # ... # App image... FROM base-image # (implicit commands)
67. # Base image... ONBUILD COPY . /app ONBUILD RUN bundle install # ... # App image... FROM base-image # (implicit commands) Tip #8: Avoid ONBUILD
68. Containers in production
69. Containers == isolation
70. Containers == isolation ⟹ predictability
71. docker run --cpus=2.0 --memory=200M ... Tip #9: Always specify resource constraints
72. apiVersion: v1 kind: Pod spec: containers: - name: rails resources: requests: memory: "100Mi" cpu: 0.5 limits: memory: "200Mi" cpu: 1.0 ...
76. Tip #10: Avoid preforking in a container ???
77. Tip #11: Scale by adding containers
78. https://pixabay.com/en/logs-timber-wood-logging-lumber-690888/ CC0
81. ENV RAILS_LOG_TO_STDOUT=true Tip #12: Log to STDOUT or an external agent
82. • Optimizing for size/performance • Container contents • Containers in production
83. http://daniel-azuma.com/railsconf2018
84. Thank you! http://daniel-azuma.com/ @danielazuma http://daniel-azuma.com/railsconf2018