急遽北海道に一週間行ってたので時間が空いてしまった。悪天候の冬の札幌駅に人生ではじめて降り立ったとき、エルデンリングの例のフォーマットで禁域って文字とドオォォォンみたいなSEが鳴った気がする。

Docker の公式チュートリアルを見つつ進める

といいつつbrewからdokcer desktop無いか確認はする。
dockerのコマンドラインツールはあるけどdocker desktop無いな。公式サイト行きましょ

https://hub.docker.com/

……動画のチュートリアルあるのか。こりゃ便利。英語だけど雰囲気でなんとかなんべ。大体見ます。

この前作ったkotlinのapiのルートに移動、以下実行

$ docker init

結果

 ~/IdeaProjects/toykotlin
$ docker init       

Welcome to the Docker Init CLI!

This utility will walk you through creating the following files with sensible defaults for your project:
  - .dockerignore
  - Dockerfile
  - compose.yaml
  - README.Docker.md

Let's get started!

? What application platform does your project use?  [Use arrows to move, type to filter]
  Go - suitable for a Go server application
  Python - suitable for a Python server application
  Node - suitable for a Node server application
  Rust - suitable for a Rust server application
  ASP.NET Core - suitable for an ASP.NET Core application
  PHP with Apache - suitable for a PHP web application
  Java - suitable for a Java application that uses Maven and packages as an uber jar
> Other - general purpose starting point for containerizing your application
  Don't see something you need? Let us know!
  Quit

kotlinなのでOtherにします。Javaともちょっと迷ったけどMavenは使ってないしね。uber jarって何？届けてくれるの？

? What application platform does your project use? Other

CREATED: .dockerignore
CREATED: Dockerfile
CREATED: compose.yaml
CREATED: README.Docker.md

✔ Your Docker files are ready!

Take a moment to review them and tailor them to your application.

When you're ready, start your application by running: docker compose up --build

Consult README.Docker.md for more information about using the generated files.

ファイルができました。中を見ます。
docker desktopのLearning centerでもこのように言っている。
however, that the Dockerfile and compose.yaml file created for your project need additional changes. In this case, you may need to look up the Dockerfile reference⁠ and Compose file reference⁠ in our documentation.

.dockerignore

# Include any files or directories that you don't want to be copied to your
# container here (e.g., local build artifacts, temporary files, etc.).
#
# For more help, visit the .dockerignore file reference guide at
# https://docs.docker.com/go/build-context-dockerignore/

**/.DS_Store
**/__pycache__
**/.venv
**/.classpath
**/.dockerignore
**/.env
**/.git
（後略）

コンテナにコピーしたくないファイルをここに記述しろと書いてあります。大体必要なものは入ってるかな？

compose.yaml

# Comments are provided throughout this file to help you get started.
# If you need more help, visit the Docker compose reference guide at
# https://docs.docker.com/go/compose-spec-reference/

# Here the instructions define your application as a service called "app".
# This service is built from the Dockerfile in the current directory.
# You can add other services your application may depend on here, such as a
# database or a cache. For examples, see the Awesome Compose repository:
# https://github.com/docker/awesome-compose
services:
  app:
    build:
      context: .
      target: final
    # If your application exposes a port, uncomment the following lines and change
    # the port numbers as needed. The first number is the host port and the second
    # is the port inside the container.
    # ports:
    #   - 8080:8080

    # The commented out section below is an example of how to define a PostgreSQL
    # database that your application can use. `depends_on` tells Docker Compose to
    # start the database before your application. The `db-data` volume persists the
    # database data between container restarts. The `db-password` secret is used
    # to set the database password. You must create `db/password.txt` and add
    # a password of your choosing to it before running `docker compose up`.
    #     depends_on:
    #       db:
    #         condition: service_healthy
    #   db:
    #     image: postgres
    #     restart: always
    #     user: postgres
    #     secrets:
    #       - db-password
    #     volumes:
    #       - db-data:/var/lib/postgresql/data
    #     environment:
    #       - POSTGRES_DB=example
    #       - POSTGRES_PASSWORD_FILE=/run/secrets/db-password
    #     expose:
    #       - 5432
    #     healthcheck:
    #       test: [ "CMD", "pg_isready" ]
    #       interval: 10s
    #       timeout: 5s
    #       retries: 5
    # volumes:
    #   db-data:
    # secrets:
    #   db-password:
    #     file: db/password.txt

ここが肝になります。docker 起動するときに必要な設定を全部ここに書いておけば、docker compose up --buildを実行するときに読んでくれます。詳しいことは公式ドキュメント見ろと書いてあります。
一番最初にやることはこれ

services:
  app:
    container_name: tamesikotlin20240122comp # この行を追加してコンテナ名を指定する

コンテナ名指定しないままbuildすると勝手に中二臭い名前にされます。

次、ポート番号

    # If your application exposes a port, uncomment the following lines and change
    # the port numbers as needed. The first number is the host port and the second
    # is the port inside the container.
    ports:
      - 8081:8080

開きたいポートがあるならコメントアウトしろと書いてますね。
前回8080ポート指定でAPI実行したので、今回は8081をフォワーディングしてくれるように設定してみます。
portsの指定場所はservices.app.portsです。字下げの位置に気をつけます。

次。

    # The commented out section below is an example of how to define a PostgreSQL
    # database that your application can use.

来ましたね。PostgreSQLを使ったマルチコンテナ的なやつ。一旦今回はDocker上でKotlin動かすことに集中し、ここは次回に回します。
composeについてはここまで。

Dockerfile

# syntax=docker/dockerfile:1

# Comments are provided throughout this file to help you get started.
# If you need more help, visit the Dockerfile reference guide at
# https://docs.docker.com/go/dockerfile-reference/

# Want to help us make this template better? Share your feedback here: https://forms.gle/ybq9Krt8jtBL3iCk7

################################################################################
# Pick a base image to serve as the foundation for the other build stages in
# this file.
#
# For illustrative purposes, the following FROM command
# is using the alpine image (see https://hub.docker.com/_/alpine).
# By specifying the "latest" tag, it will also use whatever happens to be the
# most recent version of that image when you build your Dockerfile.
# If reproducability is important, consider using a versioned tag
# (e.g., alpine:3.17.2) or SHA (e.g., alpine@sha256:c41ab5c992deb4fe7e5da09f67a8804a46bd0592bfdf0b1847dde0e0889d2bff).
FROM alpine:latest as base

################################################################################
# Create a stage for building/compiling the application.
#
# The following commands will leverage the "base" stage above to generate
# a "hello world" script and make it executable, but for a real application, you
# would issue a RUN command for your application's build process to generate the
# executable. For language-specific examples, take a look at the Dockerfiles in
# the Awesome Compose repository: https://github.com/docker/awesome-compose
FROM base as build
RUN echo -e '#!/bin/sh\n\
echo Hello world from $(whoami)! In order to get your application running in a container, take a look at the comments in the Dockerfile to get started.'\
> /bin/hello.sh
RUN chmod +x /bin/hello.sh

################################################################################
# Create a final stage for running your application.
#
# The following commands copy the output from the "build" stage above and tell
# the container runtime to execute it when the image is run. Ideally this stage
# contains the minimal runtime dependencies for the application as to produce
# the smallest image possible. This often means using a different and smaller
# image than the one used for building the application, but for illustrative
# purposes the "base" image is used here.
FROM base AS final

# Create a non-privileged user that the app will run under.
# See https://docs.docker.com/go/dockerfile-user-best-practices/
ARG UID=10001
RUN adduser \
    --disabled-password \
    --gecos "" \
    --home "/nonexistent" \
    --shell "/sbin/nologin" \
    --no-create-home \
    --uid "${UID}" \
    appuser
USER appuser

# Copy the executable from the "build" stage.
COPY --from=build /bin/hello.sh /bin/

# What the container should run when it is started.
ENTRYPOINT [ "/bin/hello.sh" ]

hello worldしかしないDockerfileが置かれています。今回やりたいのはkotlinの起動なのでまるっと書き換えます。

FROM eclipse-temurin:17.0.9_9-jre # java 17でなんか良さそうなやつ
# 適当に作業ディレクトリ
WORKDIR /app
# 作業内容全部コピー
COPY . /app/. 

# buildはあらかじめ実行しておく前提
COPY build/libs/*.jar app.jar
ENTRYPOINT ["java","-jar","/app/app.jar"]

これで実行

$ docker compose up --build

[+] Running 1/0
 ✔ Container tamesikotlin20240122comp  Recreated                                                                                                                                                                                                                      0.1s 
Attaching to tamesikotlin20240122comp
tamesikotlin20240122comp  | 
tamesikotlin20240122comp  |   .   ____          _            __ _ _
tamesikotlin20240122comp  |  /\\ / ___'_ __ _ _(_)_ __  __ _ \ \ \ \
tamesikotlin20240122comp  | ( ( )\___ | '_ | '_| | '_ \/ _` | \ \ \ \
tamesikotlin20240122comp  |  \\/  ___)| |_)| | | | | || (_| |  ) ) ) )
tamesikotlin20240122comp  |   '  |____| .__|_| |_|_| |_\__, | / / / /
tamesikotlin20240122comp  |  =========|_|==============|___/=/_/_/_/
tamesikotlin20240122comp  |  :: Spring Boot ::                (v3.2.2)
tamesikotlin20240122comp  | 
tamesikotlin20240122comp  | 2024-03-03T15:16:40.531Z  INFO 1 --- [           main] j.gooye.toy.tamesi.TamesiApplicationKt   : Starting TamesiApplicationKt v0.0.1-SNAPSHOT using Java 17.0.9 with PID 1 (/app/app.jar started by root in /app)
tamesikotlin20240122comp  | 2024-03-03T15:16:40.535Z  INFO 1 --- [           main] j.gooye.toy.tamesi.TamesiApplicationKt   : No active profile set, falling back to 1 default profile: "default"
tamesikotlin20240122comp  | 2024-03-03T15:16:41.425Z  INFO 1 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat initialized with port 8080 (http)
tamesikotlin20240122comp  | 2024-03-03T15:16:41.434Z  INFO 1 --- [           main] o.apache.catalina.core.StandardService   : Starting service [Tomcat]
tamesikotlin20240122comp  | 2024-03-03T15:16:41.435Z  INFO 1 --- [           main] o.apache.catalina.core.StandardEngine    : Starting Servlet engine: [Apache Tomcat/10.1.18]
tamesikotlin20240122comp  | 2024-03-03T15:16:41.458Z  INFO 1 --- [           main] o.a.c.c.C.[Tomcat].[localhost].[/]       : Initializing Spring embedded WebApplicationContext
tamesikotlin20240122comp  | 2024-03-03T15:16:41.459Z  INFO 1 --- [           main] w.s.c.ServletWebServerApplicationContext : Root WebApplicationContext: initialization completed in 853 ms
tamesikotlin20240122comp  | 2024-03-03T15:16:41.761Z  INFO 1 --- [           main] o.s.b.w.embedded.tomcat.TomcatWebServer  : Tomcat started on port 8080 (http) with context path ''
tamesikotlin20240122comp  | 2024-03-03T15:16:41.771Z  INFO 1 --- [           main] j.gooye.toy.tamesi.TamesiApplicationKt   : Started TamesiApplicationKt in 1.601 seconds (process running for 1.936)

なんか動いた気がする
じゃあcurlしましょ

$ curl localhost:8081/tamesi
{"message":"hello world!!"}

動きました！
明日はもうちょっといろいろDocker周りをきれいにしたいとおもいます。