Passing variable values through S3 and SQS event trigger message

Question

I have setup the aws pipeline as S3 -> SQS -> Lambda. S3 PutObject event will generate an event trigger message and pass it to SQS and SQS will trigger the lambda. I have a requirement to pass a variable value from S3 to SQS and finally to Lambda as part of the event message. Variable value could be the file name or some string value.

1. can we customize the event message json data generated by S3 event to pass some more information along with the message.
2. Does SQS just pass the event message received from S3 to Lambda or does any alteration to the message or generate its own message.
3. how to display or see the message generated by S3 in SQS or Lambda.

Answer 1

You can't manipulate the S3 event data. The schema looks like this . That will be passed onto the SQS Queue which will add some it's own metadata and pass it along to Lambda. This tutorial has a sample SQS record.

Answer 2

When Amazon S3 triggers an event, a message is sent to the desired destination (AWS Lambda, Amazon SNS, Amazon SQS). The message includes the bucket name and key (filename) of the object that triggered the event.

Here is a sample event (from Using AWS Lambda with Amazon S3 - AWS Lambda ):

{
  "Records": [
    {
      "eventVersion": "2.1",
      "eventSource": "aws:s3",
      "awsRegion": "us-east-2",
      "eventTime": "2019-09-03T19:37:27.192Z",
      "eventName": "ObjectCreated:Put",
      "userIdentity": {
        "principalId": "AWS:AIDAINPONIXQXHT3IKHL2"
      },
      "requestParameters": {
        "sourceIPAddress": "205.255.255.255"
      },
      "responseElements": {
        "x-amz-request-id": "D82B88E5F771F645",
        "x-amz-id-2": "vlR7PnpV2Ce81l0PRw6jlUpck7Jo5ZsQjryTjKlc5aLWGVHPZLj5NeC6qMa0emYBDXOo6QBU0Wo="
      },
      "s3": {
        "s3SchemaVersion": "1.0",
        "configurationId": "828aa6fc-f7b5-4305-8584-487c791949c1",
        "bucket": {
          "name": "lambda-artifacts-deafc19498e3f2df",
          "ownerIdentity": {
            "principalId": "A3I5XTEXAMAI3E"
          },
          "arn": "arn:aws:s3:::lambda-artifacts-deafc19498e3f2df"
        },
        "object": {
          "key": "b21b84d653bb07b05b1e6b33684dc11b",
          "size": 1305107,
          "eTag": "b21b84d653bb07b05b1e6b33684dc11b",
          "sequencer": "0C0F6F405D6ED209E1"
        }
      }
    }
  ]
}

The bucket can be obtained from Records[].s3.bucket.name and the key can be obtained from Records[].s3.object.key .

However, there is no capability to send a particular value, since S3 triggers the event. However, you could possibly derive a value. For example, if you had events from several different buckets triggering the Lambda function, then the Lambda function could look at the bucket name to determine why it was triggered, and then substitute a desired value.