How to Call One AWS Lambda Function from Another

So, you’re working with AWS Lambda and want to know if you can have one Lambda function call another. Short answer: absolutely! This is not only possible but also quite efficient for creating a more modular, scalable application. Let’s walk through how you can implement this using the AWS SDK.

Why Call One Lambda from Another?

Imagine you have a microservices architecture where you need to execute a series of operations that depend on each other. For instance, you have a “GenerateQuote” function that creates a price quote and an “CreateOrder” function that processes this quote into an order. You want the CreateOrder function to invoke GenerateQuote to ensure the data is accurate and trusted, thus keeping potential client manipulation at bay.

Setting Up Your Lambda Functions

Here’s how you can set up your Lambda function to call another Lambda using the AWS SDK, typically in Node.js:

1. Initialize the AWS SDK: You’ll need to require the aws-sdk package and initialize the Lambda client with the appropriate region.

   var aws = require('aws-sdk');
   var lambda = new aws.Lambda({
     region: 'us-west-2' // change this to your region
   });
   

2. Invoke the Target Lambda: Use the invoke method of the Lambda client to call the other Lambda function. You’ll pass the function name and any necessary parameters as payload.

   lambda.invoke({
     FunctionName: 'GenerateQuote', // This is the function you want to call
     Payload: JSON.stringify(requestPayload, null, 2) // This is the event data you need to pass
   }, function(error, data) {
     if (error) {
       console.log('Error calling GenerateQuote:', error);
     } else if (data.Payload) {
       console.log('Quote Generated:', data.Payload);
       // You can process the result here
     }
   });
   

3. Handle the Response: Once invoked, you’ll handle the response or any potential errors inside the callback function.

Understanding AWS Lambda Limits

When designing your solution, keep in mind AWS Lambda service limits such as execution time (currently 15 minutes), payload size (6 MB), and others. You can find the complete list of limits in the AWS Lambda quotas page.

Why Use AWS SDK?

Using the AWS SDK provides a robust, official method of invoking one Lambda function from another. It’s more reliable and maintains AWS’s security standards compared to other methods like HTTP requests, which might expose sensitive data if not handled well.

Important Considerations

• Permissions: Ensure the calling Lambda function has permission to invoke the target Lambda. You can achieve this by setting the appropriate IAM role policy.

• Error Handling: Always account for error scenarios, such as unavailability of the target Lambda function, and implement retries or fallbacks if necessary.

• Latency: Remember that calling another function incurs some latency, which might be negligible in most cases but is still worth considering in performance-sensitive applications.

By leveraging the AWS SDK, you can seamlessly orchestrate multi-step processes across multiple Lambda functions, laying the groundwork for a scalable and maintainable application architecture.