Use SNS as both trigger and destination of AWS lambda

Prerequisites

• AWS console access
• S3 bucket
• Two Amazon SNS
• Lambda configuration

Overview

SNS

Step 1: Create first SNS

• Add SNS policy

{
  "Version": "2012-10-17",
  "Id": "sns-ID",
  "Statement": [
    {
      "Sid": "Example SNS topic policy",
      "Effect": "Allow",
      "Principal": {
        "Service": "s3.amazonaws.com"
      },
      "Action": "SNS:Publish",
      "Resource": "SNS-topic-ARN",  #arn of thie created sns
      "Condition": {
        "StringEquals": {
          "aws:SourceAccount": "426857564226"
        },
        "ArnLike": {
          "aws:SourceArn": "arn:aws:s3:::prashansa-sns-bucket"
        }
      }
    }
  ]
}

*Step 2: * Go to subscription and click on create subscription

• Create subscription setting protocol as AWS Lambda that means the destination of this SNS is AWS Lambda.

Step 3: Create another SNS

• Another SNS for notifying user via email

• Set policy for this SNS

*Step 4: * Create subscription

• Set the protocol to email for this SNS to send direct notification to the user via email

S3 Bucket

*Step 5: * Create S3 bucket

Step 6: Go to properties > event notification > create event notification

Step 7: Go to Destination

• Scrolling down there is destination

Lambda

Step 8: Create lambda function

Step 9: Add trigger

• Add the first SNS whose protocol was set to lambda as trigger

Step 10: Set Lambda destination

• In the lambda destination, set the SNS secondly created that was set the protocol for email as the lambda destination

Testing

Step 11: Upload the image in S3 bucket

Step 12: Check the email for notification

References

https://repost.aws/knowledge-center/lambda-invoke-error-s3-bucket-permission