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

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2. Containerizing Rails
   Techniques, Pitfalls, & Best Practices
   Daniel Azuma
   Google Cloud Platform
   

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3. Daniel Azuma
   http://daniel-azuma.com/
   @danielazuma
   

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4. View Slide

5. Languages,
   Optimizations, and
   Libraries
   

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6. Languages,
   Optimizations, and
   Libraries
   

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7. View Slide

8. Basic concepts
   

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9. Håkan Dahlström, "Multicolored Containers"
   Source: https://www.flickr.com/photos/dahlstroms/3144199355
   License: https://creativecommons.org/licenses/by/2.0/
   

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10. Isolation
    

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11. View Slide

12. • File system
    

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13. • File system
    • CPU allocation
    

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14. • File system
    • CPU allocation
    • Memory
    

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15. • File system
    • CPU allocation
    • Memory
    • Network stack
    

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16. • File system
    • CPU allocation
    • Memory
    • Network stack
    • Users
    

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17. • File system
    • CPU allocation
    • Memory
    • Network stack
    • Users
    • Processes
    

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18. • File system
    • CPU allocation
    • Memory
    • Network stack
    • Users
    • Processes
    

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19. • File system
    • CPU allocation
    • Memory
    • Network stack
    • Users
    • Processes
    != VM
    

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20. • File system
    • CPU allocation
    • Memory
    • Network stack
    • Users
    • Processes Linux host
    

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21. • File system
    • CPU allocation
    • Memory
    • Network stack
    • Users
    • Processes
    CPU arch
    Linux kernel
    Linux host:
    

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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
    

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23. Images
    

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24. View Slide

25. Dockerfile
    

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26. # Rails Dockerfile
    FROM ruby
    WORKDIR /opt/app
    COPY . /opt/app
    RUN bundle install
    ENV PORT=8080
    CMD ["bundle", "exec",
    "rails", "server"]
    

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27. # Rails Dockerfile
    FROM ruby
    WORKDIR /opt/app
    COPY . /opt/app
    RUN bundle install
    ENV PORT=8080
    CMD ["bundle", "exec",
    "rails", "server"]
    

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28. # Rails Dockerfile
    FROM ruby
    WORKDIR /opt/app
    COPY . /opt/app
    RUN bundle install
    ENV PORT=8080
    CMD ["bundle", "exec",
    "rails", "server"]
    

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29. # Rails Dockerfile
    FROM ruby
    WORKDIR /opt/app
    COPY . /opt/app
    RUN bundle install
    ENV PORT=8080
    CMD ["bundle", "exec",
    "rails", "server"]
    

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30. # Rails Dockerfile
    FROM ruby
    WORKDIR /opt/app
    COPY . /opt/app
    RUN bundle install
    ENV PORT=8080
    CMD ["bundle", "exec",
    "rails", "server"]
    

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31. # Rails Dockerfile
    FROM ruby
    WORKDIR /opt/app
    COPY . /opt/app
    RUN bundle install
    ENV PORT=8080
    CMD ["bundle", "exec",
    "rails", "server"]
    

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32. Which base image?
    

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33. FROM ruby
    FROM alpine
    FROM phusion/baseimage
    ???
    Tip #1: Read and understand your base image
    

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34. Size does matter
    

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35. apt-get install
    

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36. RUN apt-get clean \
    && rm -f /var/lib/apt/lists/*_*
    

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37. RUN apt-get update -y
    RUN apt-get install -y -q mypackage
    RUN apt-get clean \
    && rm -f /var/lib/apt/lists/*_*
    

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38. RUN apt-get update -y \
    && apt-get install -y -q mypackage \
    && apt-get clean \
    && rm -f /var/lib/apt/lists/*_*
    

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39. FROM base-image
    

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40. FROM base-image
    RUN apt-get update
    

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41. FROM base-image
    RUN apt-get update
    RUN apt-get install mypkg
    

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42. FROM base-image
    RUN apt-get update
    RUN apt-get install mypkg
    RUN apt-get clean
    

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43. FROM base-image
    RUN apt-get update \
    && apt-get install mypkg \
    && apt-get clean
    Tip #2: Combine install commands with cleanup
    

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44. RUN apt-get install build-essential \
    && bundle install
    

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45. http://artgallery.msfc.nasa.gov/4459.html
    Source: NASA
    

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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
    

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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
    

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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
    

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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
    

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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.
    

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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.
    

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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.
    

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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
    

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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
    

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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
    

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56. Gerd Rohs, "Image in the image"
    https://pixabay.com/en/image-in-the-image-mobile-phone-2204798/
    CC0
    

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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
    

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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/
    

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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
    

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61. # Exec form
    CMD ["bundle", "exec", "rails", "s"]
    # Shell form
    CMD bundle exec rails s
    

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62. # Exec form
    CMD ["bundle", "exec", "rails", "s"]
    # Shell form
    CMD bundle exec rails s
    Tip #6: Prefer exec form for CMD
    

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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
    

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64. ONBUILD
    

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65. # Base image...
    ONBUILD COPY . /app
    ONBUILD RUN bundle install
    # ...
    

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66. # Base image...
    ONBUILD COPY . /app
    ONBUILD RUN bundle install
    # ...
    # App image...
    FROM base-image
    # (implicit commands)
    

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67. # Base image...
    ONBUILD COPY . /app
    ONBUILD RUN bundle install
    # ...
    # App image...
    FROM base-image
    # (implicit commands)
    Tip #8: Avoid ONBUILD
    

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68. Containers in
    production
    

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69. Containers == isolation
    

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70. Containers == isolation
    ⟹ predictability
    

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71. docker run --cpus=2.0 --memory=200M ...
    Tip #9: Always specify resource constraints
    

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72. apiVersion: v1
    kind: Pod
    spec:
    containers:
    - name: rails
    resources:
    requests:
    memory: "100Mi"
    cpu: 0.5
    limits:
    memory: "200Mi"
    cpu: 1.0
    ...
    

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76. Tip #10: Avoid preforking in a container
    ???
    

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77. Tip #11: Scale by adding containers
    

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78. https://pixabay.com/en/logs-timber-wood-logging-lumber-690888/
    CC0
    

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81. ENV RAILS_LOG_TO_STDOUT=true
    Tip #12: Log to STDOUT or an external agent
    

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82. • Optimizing for size/performance
    • Container contents
    • Containers in production
    

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83. http://daniel-azuma.com/railsconf2018
    

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84. Thank you!
    http://daniel-azuma.com/
    @danielazuma
    http://daniel-azuma.com/railsconf2018
    

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