Elixir on Containers

Know-how that ops Elixir on Docker containers.

Transcript

1. Elixir
   on Containers
   

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2. .｡oO(さっちゃんですよヾ(〃l _ l)ﾉﾞ☆)
   

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3. Container is good, because:
   It gives an abstract of processes with environments.
   It's easy to deploy.
   

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4. I'm using container for Elixir server @ dev, test & prod.
   A little bit stateful WebSocket servers.
   Umbrella
   Related tools: Distillery, Dialyzer, docker‑compose, Kubernetes.
   

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5. Containers for local dev
   

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6. Why use containers for local dev?
   Use the same env between Alchemist team members.
   Use the same env between non‑Alchemist team members. (Rubyist, frontend
   enginier, etc.)
   Use the near env between dev, test & prod.
   

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7. I maintain Docker images that fixes both Erlang & Elixir ver.
   

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8. Work with the team & CI (Continuous Integration).
   

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9. My application have some umbrellas.
   apps/
   app_a/
   app_b/
   

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10. Dockerfile
    (deps.compile & dialyzer ‑‑plt)
    FROM nesachirou/elixir:1.8_erl21
    SHELL ["/bin/ash", "-ex", "-o", "pipefail", "-c"]
    RUN apk add --no-cache -t .build-deps \
    ～ \
    git \
    && rm -rf /var/cache/apk/*
    WORKDIR /var/www
    VOLUME /var/www
    COPY mix.exs mix.lock ./
    COPY apps/app_a/mix.exs apps/app_a/
    COPY apps/app_b/mix.exs apps/app_b/
    RUN mix "do" deps.get, deps.compile \
    && MIX_ENV="test" mix deps.compile \
    && mix dialyzer --plt \
    && mv _build deps /tmp
    RUN apk add --no-cache -t .runtime-deps \
    inotify-tools \
    rsync \
    && rm -rf /var/cache/apk/*
    EXPOSE 4000 4001
    CMD ["./entrypoint.sh"]
    

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11. entrypoint.sh
    #!/bin/sh -eux
    # shellcheck shell=dash
    if test "$(stat /.dockerenv > /dev/null || echo $?)" ; then
    : "Outside Docker"
    mix "do" deps.get, compile
    else
    : "Inside Docker"
    rsync -au /tmp/_build /tmp/deps .
    mix "do" deps.get, compile
    fi
    elixir --name example@127.0.0.1 --cookie example -S mix phx.server
    

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12. docker-compose.yml
    ---
    version: "3"
    services:
    example:
    image: example.docker.registry/example/example:latest
    depends_on: [example-src]
    logging:
    options:
    max-size: "100m"
    max-file: "2"
    ports:
    - 4000:4000
    - 4001:4001
    volumes:
    - example-src:/var/www
    ～
    

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13. docker-compose.override.yml
    ---
    version: "3"
    services:
    example:
    build:
    context: .
    dockerfile: Dockerfiles/Dockerfile.dev
    docker-compose build --pull --force-rm
    docker-compose push
    

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14. docker‑sync
    http://docker‑sync.io/
    Docker (for MacOS) is too slow in it's file IO between containers & the host.
    docker‑sync solves this, but troublesome.
    I do a little bit different way (unison + rsync).
    

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15. docker-compose.yml
    ～
    example-src:
    image: eugenmayer/unison:2.51.2.1
    environment:
    APP_VOLUME: /app_sync
    HOST_VOLUME: /host_sync
    TZ: Asia/Tokyo
    UNISON_ARGS: |
    -debug default -ignore 'Name .git/*' -ignore 'Name _build/*' \
    -ignore 'Name deps/*' -prefer /host_sync -numericids -auto -batch
    UNISON_DEST: /app_sync
    UNISON_SRC: /host_sync
    UNISON_WATCH_ARGS: -repeat watch
    volumes:
    - ../example:/host_sync:cached
    - example-src:/app_sync
    volumes:
    example-src:
    

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16. precopy_appsync
    #!/bin/bash -eux
    rsync -auv \
    --delete \
    --exclude='.git/*' --exclude='_build/*' --exclude='deps/*' \
    /host_sync/ /app_sync
    docker-compose -f example/docker-compose.yml stop example-src
    docker-compose -f example/docker-compose.yml run --rm --no-deps example-src \
    /host_sync/tools/precopy_appsync
    docker-compose -f example/docker-compose.yml start example-src
    

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17. Testing container image
    yamllint https://github.com/adrienverge/yamllint
    hadolint https://github.com/hadolint/hadolint
    container‑structure‑test https://github.com/GoogleContainerTools/container‑
    structure‑test
    

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18. Containers for prod
    

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19. Work with CD (Continuous Delivery).
    

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20. Umbrella
    apps/
    app_a/
    app_b/
    common/
    

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21. Distillery https://github.com/bitwalker/distillery
    {:distillery, "~> 2.0", runtime: false},
    No hot code swapping, RollingUpdate.
    

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22. rel/config.exs
    ～
    environment :prod do
    set(include_erts: true)
    set(include_src: false)
    set(cookie: :"
    ～")
    set(vm_args: Path.join("rel", "vm.args.prod"))
    end
    release :app_a do
    set(version: "0.0.1")
    set(applications: [:app_a, :common, :runtime_tools])
    set(commands: [app_terminate: "rel/commands/app_terminate.sh"])
    set(overlay_vars: [
    ～])
    end
    

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23. rel/commands/app_terminate.sh
    → ./bin/app_a app_terminate
    (PreStop hook)
    #!/bin/bash -eu
    COOKIE=$(awk '/-setcookie/{print$2}' releases/0.0.1/vm.args)
    export COOKIE
    bin/app_a command Elixir.AppA.Command app_terminate
    AppA.Command
    defmodule AppA.Command do
    def app_terminate do
    :ok = do_rpc(:"app_a@127.0.0.1", :"terminate@127.0.0.1",
    AppA.AppTerminator, :request_terminate, [],
    1_800_000)
    end
    defp do_rpc(target_node, node_name, module, fun, args, timeout) do
    Node.start(node_name)
    Node.set_cookie(String.to_atom(System.get_env("COOKIE")))
    :rpc.call(target_node, module, fun, args, timeout)
    end
    end
    

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24. Dockerfile
    for app_a (multi stage build)
    FROM nesachirou/elixir:1.8_erl21 as builder
    SHELL ["/bin/ash", "-ex", "-o", "pipefail", "-c"]
    RUN apk add --no-cache -t .build-deps \
    build-base \
    ～ \
    git
    ARG REVISION
    ENV MIX_ENV=prod
    WORKDIR /var/www
    COPY mix.exs mix.lock ./
    COPY apps/app_a/mix.exs apps/app_a/
    COPY apps/common/mix.exs apps/common/
    RUN mix "do" deps.get --only prod, deps.compile
    COPY apps/app_a apps/app_a
    COPY apps/common apps/common
    COPY config config
    COPY rel rel
    # hadolint ignore=DL3003
    RUN mix compile \
    && mix release --verbose --name=app_a
    ～
    

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25. Dockerfile
    for app_a (multi stage build)
    ～
    FROM alpine:3.9
    SHELL ["/bin/ash", "-ex", "-o", "pipefail", "-c"]
    RUN apk add --no-cache -t .runtime-deps \
    bash \
    inotify-tools \
    openssl \
    && rm -rf /var/cache/apk/*
    WORKDIR /var/www
    # hadolint ignore=DL3010
    COPY --from=builder /var/www/_build/prod/rel/app_a/releases/0.0.1/app_a.tar.gz ./
    RUN tar xzf app_a.tar.gz \
    && rm -rf app_a.tar.gz
    EXPOSE 80 4369
    CMD ["bin/app_a", "foreground"]
    

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26. container-structured-test.yml
    ---
    schemaVersion: "2.0.0"
    commandTests:
    - name: Application meta data
    command: bin/example
    args: [describe]
    expectedOutput:
    - example-0.0.1
    - "Name: example_maint_@127.0.0.1"
    - name: libcrypto
    command: bin/example
    args: [eval, ":crypto.strong_rand_bytes(8)"]
    metadataTest:
    cmd: [bin/example, foreground]
    exposedPorts: ["80", "4369"]
    workdir: /var/www
    

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