実際にcloud watchのしきい値いじってもいいのですが、既存システムが感知してslack通知してしまうので、作った。

LambdaのSNSテストデータと、参考記事をあわせ一部修正したもの。
動きを試すときは、Messageの中身を変えると良いかも。

event.json

{
  "Records": [
    {
      "EventVersion": "1.0",
      "EventSubscriptionArn": "arn:aws:sns:EXAMPLE",
      "EventSource": "aws:sns",
      "Sns": {
        "SignatureVersion": "1",
        "Timestamp": "1970-01-01T00:00:00.000Z",
        "Signature": "EXAMPLE",
        "SigningCertUrl": "EXAMPLE",
        "MessageId": "95df01b4-ee98-5cb9-9903-4c221d41eb5e",
        "Message": "{\"AlarmName\":\"awsrds-app-High-DB-Connections\",\"AlarmDescription\":\"Alarm when CPU exceeds 50 percent\",\"AWSAccountId\":\"123456789123\",\"NewStateValue\":\"ALARM\",\"NewStateReason\":\"Threshold Crossed: 1 datapoint (10.0) was greater than or equal to the threshold (10.0).\",\"StateChangeTime\":\"2016-07-24T22:05:19.737+0000\",\"Region\":\"US West - Oregon\",\"OldStateValue\":\"OK\",\"Trigger\":{\"MetricName\":\"DatabaseConnections\",\"Namespace\":\"AWS/RDS\",\"Statistic\":\"AVERAGE\",\"Unit\":null,\"Dimensions\":[{\"name\":\"DBInstanceIdentifier\",\"value\":\"app\"}],\"Period\":300,\"EvaluationPeriods\":1,\"ComparisonOperator\":\"GreaterThanOrEqualToThreshold\",\"Threshold\":10.0}}",
        "MessageAttributes": {
          "Test": {
            "Type": "String",
            "Value": "TestString"
          },
          "TestBinary": {
            "Type": "Binary",
            "Value": "TestBinary"
          }
        },
        "Type": "Notification",
        "UnsubscribeUrl": "EXAMPLE",
        "TopicArn": "arn:aws:sns:EXAMPLE",
        "Subject": "TestInvoke"
      }
    }
  ]
}

参考記事

https://github.com/assertible/lambda-cloudwatch-slack/blob/master/test/sns-cloudwatch-event.json