How do I use a Lambda function to publish a message to an Amazon SNS topic?

Resolution

Follow these steps to use a Lambda function to send a message to an Amazon SNS topic.

Note: The example in this article uses a Python runtime, but you can also use your preferred Lambda runtimes.

Complete the following steps:

1. Open the Amazon SNS console.

2. Create an Amazon SNS topic.

3. On the details page, copy the Amazon Resource Name (ARN) to use in a later step.

4. Open the Lambda console.

5. Create a Lambda function.

6. On the Lambda Functions page, choose the Code tab. Then, in Code source, copy and paste the following code for the Publish boto3 action into the code editor:

   import json
   import boto3
   client = boto3.client('sns')
   def lambda_handler(event, context):
      response = client.publish(TopicArn='arn:aws:sns:your-sns-topic-arn',Message="Test message")
      print("Message published")
      return(response)

   Note: Replace your-sns-topic-arn with your Amazon SNS topic ARN that you copied in a previous step.

7. Choose Deploy.

8. Choose the Configuration tab, and then choose Permissions.

9. Choose Role name, select Add permissions, and then select Create inline policy.

10. Choose the JSON tab, and enter the following AWS Identity and Access Management (IAM) policy:

    {
        "Version": "2012-10-17",
        "Statement": [
            {
                "Sid": "PublishSNSMessage",
                "Effect": "Allow",
                "Action": "sns:Publish",
                "Resource": "arn:aws:sns:your-sns-topic-arn"
            }
        ]
    }

    Note: Replace your-sns-topic-arn with your Amazon SNS topic ARN that you copied in a previous step.

11. Choose Next, and then choose Create policy.

If your Lambda function's connected to an Amazon Virtual Private Cloud (Amazon VPC), then do one of the following:

• If your Lambda function requires internet access, then make sure that you grant internet access. For more information, see How do I give internet access to a Lambda function that's connected to an Amazon VPC?
• For private networks, create an Amazon VPC endpoint for Amazon SNS in the same VPC. Make sure that the security group for the Amazon SNS VPC endpoint allows ingress connection on port 443. For more information, see Creating an Amazon VPC endpoint for Amazon SNS.

Related information

Why do I get an authorization error when I try to subscribe my Lambda function to my Amazon SNS topic?