CloudWatch アラームがアラーム状態になった際 EventBridge の入力トランスフォーマーを使わず Step Functions でメール件名と本文をカスタマイズし SNS からメール通知する

{
  "Comment": "CloudWatch Alarm Notification Workflow",
  "StartAt": "Check Alarm State",
  "States": {
    "Check Alarm State": {
      "Type": "Choice",
      "Choices": [
        {
          "Variable": "$.detail.state.value",
          "StringEquals": "ALARM",
          "Next": "Format Message"
        }
      ],
      "Default": "Do Nothing"
    },
    "Format Message": {
      "Type": "Pass",
      "Parameters": {
        "subject.$": "States.Format('CloudWatchアラーム通知: {}', $.detail.alarmName)",
        "message.$": "States.Format('アラーム名: {}\n状態: {}\n理由: {}\n時刻: {}', $.detail.alarmName, $.detail.state.value, $.detail.state.reason, $.time)"
      },
      "Next": "Send SNS"
    },
    "Send SNS": {
      "Type": "Task",
      "Resource": "arn:aws:states:::sns:publish",
      "Parameters": {
        "TopicArn": "arn:aws:sns:ap-northeast-1:123456789012:SNS-Step-Functions-format-test",
        "Message.$": "$.message",
        "Subject.$": "$.subject"
      },
      "End": true
    },
    "Do Nothing": {
      "Type": "Pass",
      "End": true
    }
  }
}

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": [
                "logs:CreateLogDelivery",
                "logs:GetLogDelivery",
                "logs:UpdateLogDelivery",
                "logs:DeleteLogDelivery",
                "logs:ListLogDeliveries",
                "logs:PutResourcePolicy",
                "logs:DescribeResourcePolicies",
                "logs:DescribeLogGroups"
            ],
            "Resource": "*"
        }
    ]
}

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": [
                "sns:Publish"
            ],
            "Resource": [
                "arn:aws:sns:ap-northeast-1:123456789012:SNS-Step-Functions-format-test"
            ]
        }
    ]
}

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": [
                "xray:PutTraceSegments",
                "xray:PutTelemetryRecords",
                "xray:GetSamplingRules",
                "xray:GetSamplingTargets"
            ],
            "Resource": [
                "*"
            ]
        }
    ]
}

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Principal": {
                "Service": "states.amazonaws.com"
            },
            "Action": "sts:AssumeRole"
        }
    ]
}

{
  "source": [
    "aws.cloudwatch"
  ],
  "detail-type": [
    "CloudWatch Alarm State Change"
  ],
  "resources": [
    "arn:aws:cloudwatch:ap-northeast-1:123456789012:alarm:<アラーム名>"
  ]
}

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": [
                "states:StartExecution"
            ],
            "Resource": [
                "arn:aws:states:ap-northeast-1:123456789012:stateMachine:SNS-Step-Functions-format-test"
            ]
        }
    ]
}

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Principal": {
                "Service": "events.amazonaws.com"
            },
            "Action": "sts:AssumeRole"
        }
    ]
}

aws cloudwatch set-alarm-state \
  --alarm-name "<アラーム名>" \
  --state-value ALARM \
  --state-reason "test"

[cloudshell-user@ip-10-130-33-150 ~]$ aws cloudwatch set-alarm-state \
>   --alarm-name "EC2 CPUUtilization" \
>   --state-value ALARM \
>   --state-reason "test"
[cloudshell-user@ip-10-130-33-150 ~]$