The Dockerfile explosion - and the need for higher level tools

Talk from DockerCon 2016. All about the challenges of building Docker images. Discussion of the problems, what's great and not-so-great about Dockerfile, and examples of alternative tooling.

Transcript

1. The Dockerfile explosion
   Gareth
   Rushgrove
   Senior Software Engineer
   Puppet
   

   View Slide

2. The Dockerfile
   explosion and the
   need for higher
   level tools
   

   View Slide

3. Introductions
   Who am I and what am I doing here
   

   View Slide

4. @garethr
   

   View Slide

5. (without introducing more risk)
   Gareth Rushgrove
   

   View Slide

6. Built the Puppet Docker module
   

   View Slide

7. Maintain the Puppet images
   

   View Slide

8. Obsessed with metadata
   

   View Slide

9. A brief history of
   Dockerfile
   

   View Slide

10. Docker can build images
    automatically by reading the
    instructions from a Dockerfile
    From the official docs at https://docs.docker.com/engine/reference/builder/
    

    View Slide

11. A Dockerfile is a text document
    that contains all the commands a
    user could call on the command
    line to assemble an image.
    From the official docs at https://docs.docker.com/engine/reference/builder/
    

    View Slide

12. A simple Dockerfile
    FROM ubuntu
    # Install vnc, xvfb in order to create a 'fake' display and fire
    RUN apt-get update && apt-get install -y x11vnc xvfb firefox
    RUN mkdir ~/.vnc
    # Setup a password
    RUN x11vnc -storepasswd 1234 ~/.vnc/passwd
    # Autostart firefox (might not be the best way, but it does the
    RUN bash -c 'echo "firefox" >> /.bashrc'
    EXPOSE 5900
    CMD ["x11vnc", "-forever", "-usepw", "-create"]
    

    View Slide

13. Dockerfile reference
    

    View Slide

14. Commands you know
    MAINTAINER
    RUN
    CMD ["executable","param1","param2"]
    EXPOSE [...]
    ADD ...
    ENV
    WORKDIR /path/to/workdir
    USER daemon
    VOLUME ["/data"]
    ENTRYPOINT ["executable", "param1", “param2"]
    COPY ...
    

    View Slide

15. Commands you don’t know
    ONBUILD [INSTRUCTION]
    STOPSIGNAL signal
    ARG [=]
    LABEL = = = …
    HEALTHCHECK [OPTIONS] CMD command
    SHELL ["executable", "parameters"]
    

    View Slide

16. Close ALL the issues
    

    View Slide

17. Although this is not a definitive
    move, we temporarily won’t
    accept more patches to the
    Dockerfile syntax
    Docker Inc
    

    View Slide

18. HEALTHCHECK coming in 1.12
    

    View Slide

19. SHELL coming in 1.12
    

    View Slide

20. Why Dockerfiles
    are great
    

    View Slide

21. Simplicity
    FROM scratch
    COPY hello /
    CMD ["/hello"]
    

    View Slide

22. Multi-platform support
    PS> Install-PackageProvider ContainerImage -Force
    PS> Install-ContainerImage -Name WindowsServerCore
    PS> docker images
    REPOSITORY TAG IMAGE ID CREA
    windowsservercore 10.0.14300.1000 dbfee88ee9fd 7 we
    

    View Slide

23. Linting
    

    View Slide

24. Editor support
    

    View Slide

25. Why Dockerfiles
    are problematic
    

    View Slide

26. Complexity
    RUN apt-get update && \
    apt-get install -y wget=1.17.1-1ubuntu1 && \
    wget https://apt.example.com/release-"$UBUNTU_CODENAME".deb
    dpkg -i release-"$UBUNTU_CODENAME".deb && \
    rm release-"$UBUNTU_CODENAME".deb && \
    apt-get update && \
    apt-get install --no-install-recommends -y package=0.1.2 &&
    apt-get clean && \
    rm -rf /var/lib/apt/lists/*
    

    View Slide

27. Dockerfile proliferation
    

    View Slide

28. language:Dockerfile maintainer
    

    View Slide

29. 138,062
    

    View Slide

30. Only two approaches to reuse
    

    View Slide

31. Inheritance
    FROM debian:jessie
    

    View Slide

32. View Slide

33. Dockerfile is not the source of
    truth for your image
    

    View Slide

34. View Slide

35. The Dockerfile generally works
    beautifully for the class of
    problem for which it was designed
    Nathan Leclair, Docker Inc
    

    View Slide

36. Nathan Leclair, Docker Inc
    The Dockerfile is a tool for
    creating images, but it is not the
    only weapon in your arsenal
    

    View Slide

37. Putting the
    problems in
    context
    

    View Slide

38. If we dockerize all of our
    applications how many
    Dockerfiles is that?
    

    View Slide

39. If we build a complex hierarchy of
    Dockerfiles, how quickly can we
    trace/rebuild a specific image?
    

    View Slide

40. As best-practices develops how
    can we refactor our Dockefiles
    with confidence?
    

    View Slide

41. Are Dockerfiles best
    managed centrally or on a
    team-by-team basis?
    

    View Slide

42. Some community
    ideas
    

    View Slide

43. Generate
    Dockerfiles
    

    View Slide

44. Build Dockerfiles with OCAML
    

    View Slide

45. let base =
    let email = "anil@recoil.org" in
    comment "Generated by OCaml Dockerfile" @@
    from "ubuntu" ~tag:"trusty" @@
    maintainer "Anil Madhavapeddy " email
    let ocaml_ubuntu_image =
    base @@
    run "apt-get -y -qq update" @@
    run "apt-get -y install ocaml ocaml-native-compilers camlp4-ext
    onbuild (run "apt-get -y -qq update") ;;
    OCAML example
    

    View Slide

46. With Gradle
    

    View Slide

47. Or Javascript
    

    View Slide

48. Or Scala and SBT
    

    View Slide

49. Or with Python
    

    View Slide

50. - Powerful abstractions
    - Mature language tooling
    PROS
    - Need to compile down to Dockerfile
    - Everyone has their favourite language
    CONS
    

    View Slide

51. No Dockerfile
    to be seen
    

    View Slide

52. Docker Image Specification
    

    View Slide

53. View Slide

54. Packer
    

    View Slide

55. {
    "builders":[{
    "type": "docker",
    "image": "ubuntu",
    "export_path": "image.tar"
    }],
    "provisioners":[
    {
    "type": "shell",
    "inline": ["apt-get -y update; apt-get install -y puppet-co
    },
    {
    Packer example
    

    View Slide

56. Source-to-Image
    

    View Slide

57. $ s2i create
    $ s2i build [] [flags]
    $ s2i rebuild []
    $ s2i usage [flags]
    $ s2i build ./sinatra-app openshift/ruby-20-centos7 ruby-app
    s2i example
    

    View Slide

58. Nix
    

    View Slide

59. dockerTools.buildImage {
    name = "redis";
    runAsRoot = ''
    #!${stdenv.shell}
    ${dockerTools.shadowSetup}
    groupadd -r redis
    useradd -r -g redis -d /data -M redis
    mkdir /data
    chown redis:redis /data
    '';
    contents = [ redis ];
    Nix example
    

    View Slide

60. Habitat
    

    View Slide

61. - Powerful
    PROS
    - OCI image spec not final
    - Higher barrier to entry than Dockerfile
    - Limited support for things like labels
    CONS
    

    View Slide

62. Expand on
    Dockerfile
    

    View Slide

63. Rocker
    

    View Slide

64. Rocker adds some crucial
    features that are missing from
    Dockerfile while keeping
    Docker’s original design
    

    View Slide

65. FROM ubuntu:16.04
    MAINTAINER Gareth Rushgrove "gareth@puppet.com"
    ENV PUPPET_AGENT_VERSION="1.5.0" UBUNTU_CODENAME="xenial" PATH=/
    LABEL com.puppet.version="0.1.0" com.puppet.dockerfile="/Dockerf
    MOUNT /opt/puppetlabs /etc/puppetlabs /root/.gem
    RUN apt-get update && \
    apt-get install -y wget=1.17.1-1ubuntu1 && \
    wget https://apt.puppetlabs.com/puppetlabs-release-pc1-"$UBU
    Rockerfile example
    

    View Slide

66. FROM ubuntu:16.04
    MAINTAINER Gareth Rushgrove "gareth@puppet.com"
    ENV PUPPET_AGENT_VERSION="1.5.0" UBUNTU_CODENAME="xenial" PATH=/
    LABEL com.puppet.version="0.1.0" com.puppet.dockerfile="/Dockerf
    MOUNT /opt/puppetlabs /etc/puppetlabs /root/.gem
    RUN apt-get update && \
    apt-get install -y wget=1.17.1-1ubuntu1 && \
    wget https://apt.puppetlabs.com/puppetlabs-release-pc1-"$UBU
    Includes new instructions
    

    View Slide

67. rm -rf /var/lib/apt/lists/*
    EXPOSE 80
    CMD ["nginx"]
    COPY Rockerfile /Dockerfile
    TAG puppet/puppet-rocker-example
    More new instructions
    

    View Slide

68. Dockramp
    

    View Slide

69. Dockerfile pre-processors
    

    View Slide

70. $ cat Dockerfile
    FROM ubuntu:16.04
    MAINTAINER Gareth Rushgrove "gareth@puppet.com"
    ENV PUPPET_AGENT_VERSION="1.5.0" R10K_VERSION="2.2.2" \ UBUNTU_C
    PUPPET_INSTALL
    PUPPET_COPY_PUPPETFILE
    PUPPET_COPY_MANIFESTS
    PUPPET_RUN
    EXPOSE 80
    Domain-specific extensions
    

    View Slide

71. $ cat Dockerfile | dockerfilepp
    FROM ubuntu:16.04
    MAINTAINER Gareth Rushgrove "gareth@puppet.com"
    ENV PUPPET_AGENT_VERSION="1.5.0" R10K_VERSION="2.2.2" UBUNTU_COD
    RUN apt-get update && \
    apt-get install -y wget=1.17.1-1ubuntu1 && \
    wget https://apt.puppetlabs.com/puppetlabs-release-pc1-"$UBU
    dpkg -i puppetlabs-release-pc1-"$UBUNTU_CODENAME".deb && \
    rm puppetlabs-release-pc1-"$UBUNTU_CODENAME".deb && \
    apt-get update && \
    Simple expansion
    

    View Slide

72. - Simple and familiar
    - Great proving ground for upstream
    PROS
    - Still line-oriented
    - Limited tooling available (yet)
    CONS
    

    View Slide

73. The future
    Speculation and things I’d like to see
    

    View Slide

74. Formal specification for
    Dockerfile
    

    View Slide

75. RUN, FROM, COPY, etc.
    as first class API primitives
    

    View Slide

76. Opinionated workflow
    tooling around image build
    

    View Slide

77. Shared libraries and
    support for pre-processors
    

    View Slide

78. Complementary tools that
    take an organization-wide
    view of image building
    

    View Slide

79. Conclusions
    If all you take away is…
    

    View Slide

80. Dockerfile is a great starting
    point for many use cases
    

    View Slide

81. But we will need better tools for
    managing many Dockerfiles
    

    View Slide

82. And Dockerfile is just one
    interface to building images
    

    View Slide

83. Ultimately we’ll need different types
    of tools for different use cases
    

    View Slide

84. Questions?
    And thanks for listening
    

    View Slide

85. Thank you!
    

    View Slide