はじめに

GitHub ActionsからECS タスク定義(aws ecs register-task-definition)を登録する際に、jsonファイルを事前に用意する必要があります。
マネジメントコンソール上からjsonデータを取得できますが、そのままの利用はできないです。
そのため、AWS CLIを使って取得する方法について、後述します。

タスク定義ファイルの取得方法

タスク定義の最新版の情報を取得します。

TASK_DEFINITION=$(aws ecs describe-task-definition --task-definition "${タスク定義名}" --query taskDefinition)

echo $TASK_DEFINITION
{
    "taskDefinitionArn": "${タスク定義 ARN}",
    "containerDefinitions": [
        {
            "name": "${コンテナ名}",
            "image": "${アカウントID}.dkr.ecr.ap-northeast-1.amazonaws.com/${タグ名}",
            "cpu": 0,
            "portMappings": [
                {
                    "containerPort": 3000,
                    "hostPort": 3000,
                    "protocol": "tcp"
                }
            ],
            "essential": true,
            "environment": [],
            "mountPoints": [],
            "volumesFrom": [],
            "logConfiguration": {
                "logDriver": "awslogs",
                "options": {
                    "awslogs-group": "${ロググループ名}",
                    "awslogs-region": "ap-northeast-1",
                    "awslogs-stream-prefix": "ecs"
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タスク定義登録時に不要な箇所を削除し、成形します。

NEW_TASK_DEFINITION=$(echo $TASK_DEFINITION | jq --arg IMAGE "${{ secrets.AWS_ACCOUNT_ID }}.dkr.ecr.${{ env.AWS_REGION }}.amazonaws.com/${{ secrets.PROJECT }}-private-repository-${{ inputs.env_var }}:${{ github.sha }}" '
            del(.taskDefinitionArn, .revision, .status, .requiresAttributes, .compatibilities, .registeredAt, .registeredBy) |
            .containerDefinitions[0].image = $IMAGE')

echo $NEW_TASK_DEFINITION > task.json

cat task.json
{
  "containerDefinitions": [
    {
      "name": "${コンテナ名}",
      "image": "${アカウントID}.dkr.ecr.ap-northeast-1.amazonaws.com/${タグ名}",
      "cpu": 0,
      "portMappings": [
        {
          "containerPort": 3000,
          "hostPort": 3000,
          "protocol": "tcp"
        }
      ],
      "essential": true,
      "environment": [],
      "mountPoints": [],
      "volumesFrom": [],
      "logConfiguration": {
        "logDriver": "awslogs",
        "options": {
          "awslogs-group": "${ロググループ名}",
          "awslogs-region": "ap-northeast-1",
          "awslogs-stream-prefix": "ecs"
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タスク定義の登録(aws ecs register-task-definition)

タスク定義の登録を行い、完了です。

aws ecs register-task-definition --cli-input-json fileb://task.json
{
    "taskDefinition": {
        "taskDefinitionArn": "${タスク定義 ARN}",
        "containerDefinitions": [
            {
                "name": "${コンテナ名}",
                "image": "${アカウントID}.dkr.ecr.ap-northeast-1.amazonaws.com/${タグ名}",
                "cpu": 0,
                "portMappings": [
                    {
                        "containerPort": 3000,
                        "hostPort": 3000,
                        "protocol": "tcp"
                    }
                ],
                "essential": true,
                "environment": [],
                "mountPoints": [],
                "volumesFrom": [],
                "logConfiguration": {
                    "logDriver": "awslogs",
                    "options": {
                        "awslogs-group": "${ロググループ名}",
                        "awslogs-region": "ap-northeast-1",
                        "awslogs-stream-prefix": "ecs"
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jsonデータの成形を行わずに登録した場合

下記エラーが出ます。こちらを参考に、成形を行いました

aws ecs register-task-definition --cli-input-json fileb://task.json

Parameter validation failed:
Unknown parameter in input: "taskDefinitionArn", must be one of: family, taskRoleArn, executionRoleArn, networkMode, containerDefinitions, volumes, placementConstraints, requiresCompatibilities, cpu, memory, tags, pidMode, ipcMode, proxyConfiguration, inferenceAccelerators, ephemeralStorage, runtimePlatform
Unknown parameter in input: "revision", must be one of: family, taskRoleArn, executionRoleArn, networkMode, containerDefinitions, volumes, placementConstraints, requiresCompatibilities, cpu, memory, tags, pidMode, ipcMode, proxyConfiguration, inferenceAccelerators, ephemeralStorage, runtimePlatform
Unknown parameter in input: "status", must be one of: family, taskRoleArn, executionRoleArn, networkMode, containerDefinitions, volumes, placementConstraints, requiresCompatibilities, cpu, memory, tags, pidMode, ipcMode, proxyConfiguration, inferenceAccelerators, ephemeralStorage, runtimePlatform
Unknown parameter in input: "requiresAttributes", must be one of: family, taskRoleArn, executionRoleArn, networkMode, containerDefinitions, volumes, placementConstraints, requiresCompatibilities, cpu, memory, tags, pidMode, ipcMode, proxyConfiguration, inferenceAccelerators, ephemeralStorage, runtimePlatform
Unknown parameter in input: "compatibilities", must be one of: family, taskRoleArn, executionRoleArn, networkMode, containerDefinitions, volumes, placementConstraints, requiresCompatibilities, cpu, memory, tags, pidMode, ipcMode, proxyConfiguration, inferenceAccelerators, ephemeralStorage, runtimePlatform
Unknown parameter in input: "registeredAt", must be one of: family, taskRoleArn, executionRoleArn, networkMode, containerDefinitions, volumes, placementConstraints, requiresCompatibilities, cpu, memory, tags, pidMode, ipcMode, proxyConfiguration, inferenceAccelerators, ephemeralStorage, runtimePlatform
Unknown parameter in input: "registeredBy", must be one of: family, taskRoleArn, executionRoleArn, networkMode, containerDefinitions, volumes, placementConstraints, requiresCompatibilities, cpu, memory, tags, pidMode, ipcMode, proxyConfiguration, inferenceAccelerators, ephemeralStorage, runtimePlatform

GitHub Actionsからタスク定義を登録する時の実装

GitHub Actionsからの実装の場合は、ECRのURIを更新する場合がほとんどかと思います。
下記が更新例のため、ご参考程度に載せておきます。

          # タスク定義ファイルを読み込む
          TASK_DEFINITION=$(cat ${{ github.workspace }}/.github/workflows/ecs_task_definition/task_definition.json)

          # イメージを更新
          NEW_TASK_DEFINITION=$(echo "$TASK_DEFINITION" | jq --arg IMAGE "${{ secrets.AWS_ACCOUNT_ID }}.dkr.ecr.${{ env.AWS_REGION }}.amazonaws.com/${{ secrets.PROJECT }}-private-repository-${{ inputs.env_var }}:${{ github.sha }}" '
            .containerDefinitions[0].image = $IMAGE
          ')

          # 新しいタスク定義を登録
          NEW_TASK_DEFINITION_ARN=$(aws ecs register-task-definition --cli-input-json "$NEW_TASK_DEFINITION" --query 'taskDefinition.taskDefinitionArn' --output text)
          echo "NEW_TASK_DEFINITION_ARN=$NEW_TASK_DEFINITION_ARN" >> "$GITHUB_ENV"