Thinking inside the box: Dockerizing Perl

Docker provides a lightweight environment for running Perl, but the documentation for starts with a full copy of Ubuntu! Instead of treating docker containers as VM's we can build a minimal container that works as a base for running applications with Perl.

This talk describes the basics of building a new container with a few alternatives for using an O/S image, busybox, libraries, or nothing to run Perl.

Transcript

1. Thinking inside the box: Dockerizing Perl
   Steven Lembark
   Workhorse Computing
   lembark@wrkhors.com
   

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2. What's on your box?
   Pre-compiled perl distros are terrible.
   Bulky, slow, with annoying dependencies.
   Not what you need...
   

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3. Example: Red Hat Enterprize 7.0
   5.16 == “end of life”
   -Doptimize=-O2 -g -pipe -fstack-
   protector-strong -mtune=generic -
   Dversion=5.16.3 -Dmyhostname=localhost
   -Dperladmin=root@localhost -
   Dusethreads -Duseithreads -
   Ubincompat5005
   

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4. Example: Red Hat Enterprize 7.0
   5.16 == “end of life”
   Not exactly built for speed.
   -Doptimize=-O2 -g -pipe -fstack-
   protector-strong -mtune=generic -
   Dversion=5.16.3 -Dmyhostname=localhost
   -Dperladmin=root@localhost -
   Dusethreads -Duseithreads -
   Ubincompat5005
   

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5. Example: Red Hat Enterprize 7.0
   5.16 == “end of life”
   Not exactly built for speed.
   Thread overhead, even if you don't use them.
   -Doptimize=-O2 -g -pipe -fstack-
   protector-strong -mtune=generic -
   Dversion=5.16.3 -Dmyhostname=localhost
   -Dperladmin=root@localhost -
   Dusethreads -Duseithreads -
   Ubincompat5005
   

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6. Fresh, not frozen
   perl for your architecture.
   optimized.
   only dependencies you use (need).
   Q: How?
   

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7. Try it, you'll like it...
   Bad approach: virtual machines...
   

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8. Try it, you'll like it...
   Bad approach: virtual machines...
   and version-dirs...
   and recompiling for each distro, architecture...
   and symlink hell(2)...
   and …
   

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9. Try it, you'll like it...
   False lazyness!
   

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10. Tasty alternative: lxc
    Essentially an LPAR – we've come full circle.
    Use a process to isolate & localize code.
    Share the kernel.
    Light weight, fast startup, easy to ship.
    

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11. Fly in the soup
    Ever try to use lxc?
    Let alone finish the manpages?
    Kills my appetite.
    RTFM
    lxc-attach.1
    lxc-autostart.1
    lxc-cgroup.1
    lxc-checkconfig.1
    lxc-checkpoint.1
    lxc-clone.1
    lxc-config.1
    lxc-console.1
    lxc-create.1
    lxc-destroy.1
    lxc-device.1
    lxc-execute.1
    lxc-freeze.1
    lxc-info.1
    lxc-ls.1
    lxc-monitor.1
    lxc-snapshot.1
    lxc-start-ephemeral.1
    lxc-start.1
    lxc-stop.1
    lxc-top.1
    lxc-unfreeze.1
    lxc-unshare.1
    lxc-user-nic.1
    lxc-usernet.5
    lxc-usernsexec.1
    lxc-wait.1
    lxc.7
    lxc.conf.5
    lxc.container.conf.5
    lxc.system.conf.5
    

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12. Docker: MRE for linux
    80/20 of lxc:
    Layered filesystem + Repository + Command line.
    More nutritious than exciting.
    Still evolving.
    

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13. Catch: Docker's Docs aren't lean!
    Docker doc's start with ubuntu image.
    1.6GiB – Heart attack on a plate!
    Includes X11 libs, lvm, mdadm, grub, parted... perl.
    

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14. A: There is more than one way to do it.
    Dockerfile builds perl on a light[er] weight O/S.
    Single package for perl + shared libs.
    Shell tools available for qx{...}.
    Still pretty heavy-weight.
    

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15. A: There is more than one way to do it.
    Copy perl on top of busybox.
    Much leaner cuisine.
    Decent collection of shell tools.
    Shared lib's as layer or via -v.
    

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16. A: There is more than one way to do it.
    Just perl
    No empty calories.
    Dodge library issues with -v or static compile.
    Lacks tools to inspect the build.
    

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17. Start by getting docker.
    They provide shell code for the basics:
    $curl -sL https://get.docker.io/ | sh;
    $wget -qO- https://get.docker.io/ | sh;
    will do the deed on Fedora, Ubuntu/Debian, or Gentoo.
    Also need to sanity check the kernel.
    

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18. Be yourself
    Don't run as su.
    Add your users to “docker” in /etc/group.
    After that check that docker is running:
    $ docker ps;
    Get access to the repository:
    $ docker login;
    

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19. Just a taste...
    Minimal base container: busybox.
    Good for experimenting:
    $ docker pull busybox
    Pulling repository busybox
    fd5373b3d938: Download complete
    ...
    f06b02872d52: Download complete
    

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20. Getting inside the box
    # /bin/sh is entrypoint
    $ docker run -t -i busybox;
    # <-- su in box, login id out.
    # ping 8.8.8.8; <-- network available.
    ...
    # exit; <-- exit docker process
    $ <-- original EUID
    

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21. Gentoo is easy to dockerize
    Common solution is a “stage-3” system.
    Shell + libs + build tools.
    Not much else.
    About half the size of Ubuntu.
    

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22. Finding a distribution
    Start at the docker registry
    https://registry.hub.docker.com/
    Looking for stage-3 builds:
    https://registry.hub.docker.com/search?q=gentoo+stage3
    I find:
    jgkim/gentoo-stage3 741.2 MB
    Reasonable start.
    

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23. Grabbing an O/S
    Get the image:
    $ docker pull jgkim/gentoo-stage3;
    Run a container:
    $ docker run –rm -i -t jgkim/gentoo-stage3;
    # gcc --version;
    gcc 4.8.4 good supports “--arch=native”
    

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24. Building a perl container
    Github has templates:
    http://github.com/Perl/docker-perl
    Dockerfiles like “5.020.000-64bit/Dockerfile”.
    git acquires “5.02.0-64bit-optimized” directory.
    

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25. FROM buildpack-deps # parent container
    RUN apt-get update && apt-get install -y curl procps # commands to pull perl
    RUN mkdir /usr/src/perl
    WORKDIR /usr/src/perl # build dir within the container
    RUN curl -SL http://www.cpan.org/src/5.0/perl-5.20.0.tar.gz | tar -xz --strip-components=1
    RUN ./Configure -Duse64bitall -des \
    && make -j$(nproc) && TEST_JOBS=$(nproc) make test_harness \
    && make install && make veryclean
    WORKDIR /root
    CMD ["perl5.20.0","-de0"] # /bin/sh perl5.20.0 -de0
    Distro's Dockerfile
    

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26. Check the local arguments
    $ perl -V;
    ...
    config_args='-de -Dprefix=/opt/perl/5.20 -
    Doptimize=-O3 -march=native -pipe'
    perl -MConfig -E 'say $Config{ config_args }'
    

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27. New Dockerfile
    FROM jgkim/gentoo-stage3
    MAINTAINER Steven Lembark
    WORKDIR /var/tmp/
    RUN wget http://www.cpan.org/src/5.0/perl-5.20.2.tar.gz;
    RUN gzip -dc < perl-5.20.2.tar.gz | tar xf -;
    RUN cd perl-5.20.2 && \
    ./Configure -de -Dprefix=/opt/perl \
    -Dman1dir=none -Dman3dir=none \
    -Doptimize='-O3 -march=native -pipe' ;
    RUN make -C perl-5.20.2 all test install distclean;
    RUN /opt/perl/bin/h2ph -r -l /usr/include;
    CMD [ "/opt/perl/bin/perl", "-d", "-E", "42" ]
    

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28. Building Perl
    The build takes input and optional repository tag.
    Input is a directory not “Dockerfile”
    $ cd /scratch/docker/gentoo+perl;
    $ docker build –tag='lembark/perl-gentoo' . ;
    Each step in the Dockerfile is an intermediate image.
    

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29. Checking local containers
    Intermediate images labled with “”.
    These were from prior tests.
    This one didn't finish:
    $ docker images
    REPOSITORY TAG IMAGE ID CREATED VIRTUAL SIZE
    5906d8edbb59 10 minutes ago 726.1 MB
    10f5517fcada 23 minutes ago 726.1 MB
    7d328e761704 26 minutes ago 725.5 MB
    88f1e41aaed5 27 minutes ago 725.5 MB
    28052ace7e04 28 minutes ago 725.5 MB
    6f46836220d9 31 minutes ago 725.5 MB
    

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30. $ docker build --rm=false –tag=lembark/perl:5.20 .;
    Step 0 : FROM rndevfx/gentoo-stage3-amd64-nomultilib
    ---> e9d0ce66148c
    Step 1 : MAINTAINER Steven Lembark
    ---> Using cache <-- recycled image
    ---> 41d5480e49e7
    Step 2 : WORKDIR /var/tmp
    ---> Using cache
    ---> 010d3d70ced1
    ...
    Step 7 : RUN make all test install; <-- first execution is here.
    ---> Running in 949c9ddfc2ef
    Step 8 : RUN /opt/perl/bin/h2ph -r -a -l;
    ---> Running in b084569e8fc3
    -r and -a options are mutually exclusive
    INFO[1342] The command [/bin/sh -c /opt/perl/bin/h2ph -r -a -l;] returned a non-zero code
    oops...
    

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31. Easy fix
    RUN /opt/perl/bin/h2ph -r -l /usr/inlcude;
    

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32. True Lazyness
    Re-running “build” re-cycles images:
    ...
    Step 7 : RUN make all test install;
    ---> Using cache
    ---> cb4c5cd0607e
    Step 8 : RUN /opt/perl/bin/h2ph -r -l /usr/include;
    ---> Running in 92efee8c31e2
    require '_h2ph_pre.ph';
    ...
    

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33. And impatience
    $ time docker build --rm=false --tag=lembark/perl-gentoo .
    Sending build context to Docker daemon 4.096 kB
    Sending build context to Docker daemon
    Step 0 : FROM rndevfx/gentoo-stage3-amd64-nomultilib
    ...
    Step 10 : CMD [ “/opt/perl/bin/perl” ]
    ---> Using cache
    ---> f7b83ecbe276
    Successfully built f7b83ecbe276
    real 0m0.241s
    user 0m0.019s
    sys 0m0.012
    

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34. Docker Images:
    REPOSITORY VIRTUAL SIZE
    lemark/gentoo-perl 884.8 MB
    jgkim/gentoo-stage3 741.2 MB
    localhost:5000/lembark/busybox 1.9 MB
    Adding “RUN rm -rf perl-5.20.2”:
    lemark/gentoo-perl 884.8 MB
    Cannot reclaim build space!
    Successful build: tagged image
    

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35. Welcome to perl
    “CMD” gets run with an interactive container:
    $ docker run –rm -i -t lembark/gentoo-perl;
    Loading DB routines from perl5db.pl version 1.44
    Editor support available.
    ...
    main::(-e:1): 0
    DB<1> x $^V
    v5.20.2
    

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36. Choose your toppings
    Default for gentoo run /bin/bash .
    Save typing with:
    ENTRYPOINT [ “/opt/perl/bin/perl” ]
    CMD [ "-d", "-E", "42" ]
    And then:
    docker run –rm -i -t lembark/docker-perl;
    Use –entrypoint='/bin/bash' if perl fails.
    

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37. The next course
    Stacked images inherit the ENTRYPOINT:
    FROM lembark/gentoo-perl
    CMD [ "/path/to/your/perl_code" ]
    

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38. Test containers stack
    Derive tests from the package.
    Add ./t to another image.
    ENTRYPOINT [ "/opt/perl/bin/prove" ]
    Result: no tests in product image:
    docker run foo/bar; run application.
    docker run foo/bar-test; run base tests.
    

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39. Lighter, reasonably tasty...
    But still way, way too high-calorie.
    You already have a local O/S.
    Q: Why add one to the container?
    A: Because we are all used to virtual machines.
    Time for really lean cuisine.
    

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40. Copy perl on top of busybox
    Build & install into /opt/perl.
    Add /opt/perl/Dockerfile:
    FROM lembark/busybox_x86
    COPY [ “.”, “/opt/perl” ]
    $ docker build /opt/perl lembark/busybox-perl;
    

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41. Nice combination
    Useful shell tools for "qx".
    Examine broken perl with /bin/sh entrypoint.
    

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42. Nothing artificial, nothing added
    Build a naked /opt/perl.
    Leave out “busybox”:
    FROM lembark/empty;
    COPY [ “.”, “/opt/perl” ]
    Minimal base for Plack or coros.
    

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43. Shared libs
    Catch: perl usually needs them.
    In my case, from /lib64.
    One way: O/S base image.
    Q: How else?
    

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44. Fix: Share libs
    Run containers with read-only mount of /lib64:
    docker run -v /lib64:/lib64:r …
    Light-weight.
    Fast: No images to ship.
    Homogenous lib's.
    

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45. Fix: Add libs
    “ldd” lists shared libs.
    COPY them into the image with perl.
    Build perl from a lib64 image.
    linux-vdso.so.1 (0x00007ffdfbbcb000)
    libperl.so => /opt/perl/5.20/lib/5.20.2/x86_64-linux/CORE/libperl.so
    (0x00007f40f8868000)
    libnsl.so.1 => /lib64/libnsl.so.1 (0x00007f40f8650000)
    libdl.so.2 => /lib64/libdl.so.2 (0x00007f40f844c000)
    libm.so.6 => /lib64/libm.so.6 (0x00007f40f8153000)
    libcrypt.so.1 => /lib64/libcrypt.so.1 (0x00007f40f7f1c000)
    libutil.so.1 => /lib64/libutil.so.1 (0x00007f40f7d19000)
    libc.so.6 => /lib64/libc.so.6 (0x00007f40f7981000)
    /lib64/ld-linux-x86-64.so.2 (0x00007f40f8c2b000)
    

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46. Fix: static perl
    Add “--static”.
    No hetergenious server issues.
    perl image is larger.
    Container has same virtual size.
    Best for tests: no issues with underlying images.
    

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47. Result: portable, optimized, minimal perl.
    Static perl with busybox: < 250 MiB.
    Including Dancer, mod_perl, and friends.
    Whole lot less than Ubuntu.
    Not a virtual machine.
    Plack web server FROM this perl.
    Viola!, you're up.
    

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48. References
    http://docs.docker.com/
    .../builder Dockerfile directives
    .../userguide What you think it is.
    

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49. Summary
    Docker makes lxc approachable.
    perl on busybox is tasty, low-calorie.
    Add /lib64 for a complete meal.
    

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