Lambda Destinations

Introduction

AWS Lambda Destinations provide a way to route the results of asynchronous Lambda function invocations to specific destinations. This feature enhances the flexibility and robustness of serverless applications by allowing developers to define what happens to the results of their Lambda functions based on success or failure conditions.

Key Concepts

• **Asynchronous Invocations**: Lambda functions can be invoked asynchronously, meaning that the caller does not wait for the function to complete.
• **Destinations**: The destination can be an AWS service like SQS, SNS, Lambda, or EventBridge, which handles the results of the invocation.
• **Failure Handling**: Developers can set up different destinations for successful and failed invocations, enabling better error handling.

Configuration

To configure Lambda Destinations, follow these steps:

1. Open the AWS Lambda console.
2. Select the function you want to configure.
3. Under the "Configuration" tab, find the "Asynchronous invocation" section.
4. Set up the destination for Success and/or Failure based on your requirements.

Example Configuration

{
    "DestinationConfig": {
        "OnSuccess": {
            "Destination": "arn:aws:sqs:us-east-1:123456789012:my-queue"
        },
        "OnFailure": {
            "Destination": "arn:aws:sns:us-east-1:123456789012:my-topic"
        }
    }
}
            

Examples

Example 1: Sending to SQS

const AWS = require('aws-sdk');
const sqs = new AWS.SQS();

exports.handler = async (event) => {
    // Your business logic here
    const result = { status: 'success', data: event };
    
    // Send success result to SQS
    await sqs.sendMessage({
        QueueUrl: 'https://sqs.us-east-1.amazonaws.com/123456789012/my-queue',
        MessageBody: JSON.stringify(result)
    }).promise();
};
            

Example 2: Sending to SNS

const AWS = require('aws-sdk');
const sns = new AWS.SNS();

exports.handler = async (event) => {
    // Your business logic here
    const result = { status: 'failure', error: 'An error occurred' };
    
    // Notify via SNS on failure
    await sns.publish({
        TopicArn: 'arn:aws:sns:us-east-1:123456789012:my-topic',
        Message: JSON.stringify(result)
    }).promise();
};
            

Best Practices

• **Use Dead Letter Queues (DLQs)**: Configure DLQs for failure destinations to capture failed messages for later processing.
• **Monitor and Log**: Utilize AWS CloudWatch to monitor the invocations and set up alarms for failures.
• **Test Thoroughly**: Always test the configuration in a development environment before deploying to production.

FAQ

Flowchart

graph TD;
    A[Start] --> B{Is Lambda async?};
    B -- Yes --> C[Route to Success or Failure Destination];
    B -- No --> D[End];
    C --> E[Success Destination];
    C --> F[Failure Destination];