【Rails】ECS環境にGithubActionsで自動デプロイしよう

目標

ECSに対して、Railsアプリを自動デプロイしていきます。
mainブランチにソースがマージされたことをトリガにECSにデプロイしていきます。

前提

AWSでECS環境（タスク定義/ECR/クラスター/サービス）が作成済みであること
※今回はAWS上のタスク定義を取得して、タスク定義の更新をかける。

実装

基本的には、GithubActionのテンプレで用意されているものをそのまま使用します。

◯テンプレの場所
Githubリポジトリ Action配下 [New workflow]ボタンを押下

ECSと検索

中身はほぼこれです。
テンプレから修正した箇所は「■修正: xxx」と書いています。

# This workflow will build and push a new container image to Amazon ECR,
# and then will deploy a new task definition to Amazon ECS, when there is a push to the "main" branch.
#
# To use this workflow, you will need to complete the following set-up steps:
#
# 1. Create an ECR repository to store your images.
#    For example: `aws ecr create-repository --repository-name my-ecr-repo --region us-east-2`.
#    Replace the value of the `ECR_REPOSITORY` environment variable in the workflow below with your repository's name.
#    Replace the value of the `AWS_REGION` environment variable in the workflow below with your repository's region.
#
# 2. Create an ECS task definition, an ECS cluster, and an ECS service.
#    For example, follow the Getting Started guide on the ECS console:
#      https://us-east-2.console.aws.amazon.com/ecs/home?region=us-east-2#/firstRun
#    Replace the value of the `ECS_SERVICE` environment variable in the workflow below with the name you set for the Amazon ECS service.
#    Replace the value of the `ECS_CLUSTER` environment variable in the workflow below with the name you set for the cluster.
#
# 3. Store your ECS task definition as a JSON file in your repository.
#    The format should follow the output of `aws ecs register-task-definition --generate-cli-skeleton`.
#    Replace the value of the `ECS_TASK_DEFINITION` environment variable in the workflow below with the path to the JSON file.
#    Replace the value of the `CONTAINER_NAME` environment variable in the workflow below with the name of the container
#    in the `containerDefinitions` section of the task definition.
#
# 4. Store an IAM user access key in GitHub Actions secrets named `AWS_ACCESS_KEY_ID` and `AWS_SECRET_ACCESS_KEY`.
#    See the documentation for each action used below for the recommended IAM policies for this IAM user,
#    and best practices on handling the access key credentials.

name: Deploy to Amazon ECS

on:
  push:
    branches: [ "main", "feature/sato#xxx-impl_ecs_deploy" ]

# ■修正: 変数に自身のAWS情報を設定する。
env:
  AWS_REGION: リージョン名                   # set this to your preferred AWS region, e.g. us-west-1
  ECR_REPOSITORY: ECRリポジトリ名               # set this to your Amazon ECR repository name
  ECS_SERVICE: ECSサービス名                  # set this to your Amazon ECS service name
  ECS_CLUSTER: ECSクラスター名                  # set this to your Amazon ECS cluster name
  ECS_TASK_DEFINITION: タスク定義名          # set this to the path to your Amazon ECS task definition
                                               # file, e.g. .aws/task-definition.json
  CONTAINER_NAME: コンテナ名                         # set this to the name of the container in the
                                               # containerDefinitions section of your task definition

permissions:
  contents: read

jobs:
  deploy:
    name: Deploy
    runs-on: ubuntu-latest
    environment: production

    steps:
    - name: Checkout
      uses: actions/checkout@v4

    - name: Configure AWS credentials
      uses: aws-actions/configure-aws-credentials@v1
      with:
        aws-access-key-id: ${{ secrets.AWS_ACCESS_KEY_ID }}
        aws-secret-access-key: ${{ secrets.AWS_SECRET_ACCESS_KEY }}
        aws-region: ${{ env.AWS_REGION }}

    - name: Login to Amazon ECR
      id: login-ecr
      uses: aws-actions/amazon-ecr-login@v1

    - name: Build, tag, and push image to Amazon ECR
      id: build-image
      env:
        ECR_REGISTRY: ${{ steps.login-ecr.outputs.registry }}
        IMAGE_TAG: ${{ github.sha }}
      run: |
        # Build a docker container and
        # push it to ECR so that it can
        # be deployed to ECS.
        # ■修正: docker buildは各々のアプリでのビルド方法に適宜修正
        docker build --build-arg RAILS_MASTER_KEY=${{ secrets.RAILS_MASTER_KEY }} --build-arg RAILS_ENV=production --platform linux/amd64 -t $ECR_REGISTRY/$ECR_REPOSITORY:$IMAGE_TAG .
        docker push $ECR_REGISTRY/$ECR_REPOSITORY:$IMAGE_TAG
        echo "image=$ECR_REGISTRY/$ECR_REPOSITORY:$IMAGE_TAG" >> $GITHUB_OUTPUT

    # ■修正: AWSのタスク定義jsonを取得するstepを追加
    - name: Latest ECS task definition Json
      run: aws ecs describe-task-definition --task-definition ${{ env.ECS_TASK_DEFINITION }} --query taskDefinition > taskdefinition.json

    - name: Fill in the new image ID in the Amazon ECS task definition
      id: task-def
      uses: aws-actions/amazon-ecs-render-task-definition@v1
      with:
        task-definition: taskdefinition.json
        container-name: ${{ env.CONTAINER_NAME }}
        image: ${{ steps.build-image.outputs.image }}

    - name: Deploy Amazon ECS task definition
      uses: aws-actions/amazon-ecs-deploy-task-definition@v1
      with:
        task-definition: ${{ steps.task-def.outputs.task-definition }}
        service: ${{ env.ECS_SERVICE }}
        cluster: ${{ env.ECS_CLUSTER }}
        wait-for-service-stability: true

AWSへのアクセス情報とRailsのマスターキーだけ、Githubリポジトリのシークレットに保存しておく必要があります。

AWS_ACCESS_KEY_ID
AWS_SECRET_ACCESS_KEY
RAILS_MASTER_KEY

Github -> Setting -> Repository secrets

以上。

あとはDockerがちゃんと動いてさえいるのであれば、ECS上で動作するはずです！