Using Amazon Lambda with Amazon SNS

You can use a Lambda function to process Amazon Simple Notification Service (Amazon SNS) notifications. Amazon SNS supports Lambda functions as a target for messages sent to a topic. You can subscribe your function to topics in the same account or in other Amazon accounts.

Amazon SNS invokes your function asynchronously with an event that contains a message and metadata.

{
  "Records": [
    {
      "EventVersion": "1.0",
      "EventSubscriptionArn": "arn:aws-cn:sns:cn-north-1:123456789012:sns-lambda:21be56ed-a058-49f5-8c98-aedd2564c486",
      "EventSource": "aws:sns",
      "Sns": {
        "SignatureVersion": "1",
        "Timestamp": "2019-01-02T12:45:07.000Z",
        "Signature": "tcc6faL2yUC6dgZdmrwh1Y4cGa/ebXEkAi6RibDsvpi+tE/1+82j...65r==",
        "SigningCertUrl": "https://sns.cn-north-1.amazonaws.com.cn/SimpleNotificationService-ac565b8b1a6c5d002d285f9598aa1d9b.pem",
        "MessageId": "95df01b4-ee98-5cb9-9903-4c221d41eb5e",
        "Message": "Hello from SNS!",
        "MessageAttributes": {
          "Test": {
            "Type": "String",
            "Value": "TestString"
          },
          "TestBinary": {
            "Type": "Binary",
            "Value": "TestBinary"
          }
        },
        "Type": "Notification",
        "UnsubscribeUrl": "https://sns.cn-north-1.amazonaws.com.cn/?Action=Unsubscribe&SubscriptionArn=arn:aws-cn:sns:cn-north-1:123456789012:test-lambda:21be56ed-a058-49f5-8c98-aedd2564c486",
        "TopicArn":"arn:aws-cn:sns:cn-north-1:123456789012:sns-lambda",
        "Subject": "TestInvoke"
      }
    }
  ]
}

For asynchronous invocation, Lambda queues the message and handles retries. If Amazon SNS can't reach Lambda or the message is rejected, Amazon SNS retries at increasing intervals over several hours. For details, see Reliability in the Amazon SNS FAQs.

To perform cross-account Amazon SNS deliveries to Lambda, you must authorize Amazon SNS to invoke your Lambda function. In turn, Amazon SNS must allow the Amazon account with the Lambda function to subscribe to the Amazon SNS topic. For example, if the Amazon SNS topic is in account A and the Lambda function is in account B, both accounts must grant permissions to the other to access their respective resources. Since not all the options for setting up cross-account permissions are available from the Amazon Web Services Management Console, you must use the Amazon Command Line Interface (Amazon CLI) for setup.

For more information, see Fanout to Lambda functions in the Amazon Simple Notification Service Developer Guide.