Cloudwatch: event type syntax for monitoring S3 files

Question

I need to create a cloudwatch event that runs a lambda function everytime my file in S3 gets updated/re-uploaded. What "eventName" should I use? I tried using "ObjectCreated" but it doesn't seem to work. Perhaps the syntax is incorrect.

https://docs.aws.amazon.com/AmazonS3/latest/API/API_GetObject.html

{
  "source": [
    "aws.s3"
  ],
  "detail-type": [
    "AWS API Call via CloudTrail"
  ],
  "detail": {
    "eventSource": [
      "s3.amazonaws.com"
    ],
    "eventName": [ "ObjectCreated:*"],
    "requestParameters": {
      "bucketName": [
        "mynewbucket"
      ],
      "key": [
        "file.csv"
      ]
    }
  }
}

Answer 1

CloudWatch Events (or EventBridge) does not automatically track data events for S3 objects. You need to either use CloudTrail for this, which tracks data events on a particular S3 bucket and emits CloudWatch Events (or EventBridge) events for that: https://aws.amazon.com/blogs/compute/using-dynamic-amazon-s3-event-handling-with-amazon-eventbridge/

Or you can use S3 Event Notifications with an SNS topic and use a Lambda subscription on the SNS topic.