This document discusses using containers for local development and production of Elixir applications. It recommends using containers to provide consistent environments for development teams. It also describes building and deploying multi-stage Docker images for Elixir apps with Umbrella projects using tools like Distillery, and testing container images with tools like container-structure-test. Containers provide isolation that helps ensure consistency across environments from development to production.

1. Elixir
onContainers

2. .｡oO(さっちゃんですよヾ(〃l_l)ﾉﾞ☆)

3. Containerisgood,because:
Itgivesanabstractofprocesseswithenvironments.
It'seasytodeploy.

4. I'musingcontainerforElixirserver@dev,test&prod.
AlittlebitstatefulWebSocketservers.
Umbrella
Relatedtools:Distillery,Dialyzer,docker‑compose,Kubernetes.

5. Containersforlocaldev

6. Whyusecontainersforlocaldev?
UsethesameenvbetweenAlchemistteammembers.
Usethesameenvbetweennon‑Alchemistteammembers.(Rubyist,frontend
enginier,etc.)
Usethenearenvbetweendev,test&prod.

7. ImaintainDockerimagesthatfixesbothErlang&Elixirver.

8. Workwiththeteam&CI(ContinuousIntegration).

9. Myapplicationhavesomeumbrellas.
apps/
app_a/
app_b/

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"]

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

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
～

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

14. docker‑sync
http://docker‑sync.io/
Docker(forMacOS)istooslowinit'sfileIObetweencontainers&thehost.
docker‑syncsolvesthis,buttroublesome.
Idoalittlebitdifferentway(unison+rsync).

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:

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

17. Testingcontainerimage
yamllinthttps://github.com/adrienverge/yamllint
hadolinthttps://github.com/hadolint/hadolint
container‑structure‑testhttps://github.com/GoogleContainerTools/container‑
structure‑test

18. Containersforprod

19. WorkwithCD(ContinuousDelivery).

20. Umbrella
apps/
app_a/
app_b/
common/

21. Distilleryhttps://github.com/bitwalker/distillery
{:distillery, "~> 2.0", runtime: false},
Nohotcodeswapping,RollingUpdate.

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

23. rel/commands/app_terminate.sh → ./bin/app_a app_terminate (PreStophook)
#!/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

24. Dockerfile forapp_a(multistagebuild)
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
～

25. Dockerfile forapp_a(multistagebuild)
～
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"]

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