Calling Lambda Function from another Lambda Function synchronously - Node.js

AWS Lambda functions are very useful when you work with Alexa or SageMaker or for any serverless applications.
But if you have multiple Lambdas & wanted to call one from another, how to do it?
Lets find out.

AWS sdk provides a way to invoke Lambda, so we first need to import AWS sdk.

	var AWS = require('aws-sdk');
	AWS.config.region = 'us-east-2';
	var lambda = new AWS.Lambda();

view raw lambda-header.js hosted with ❤ by GitHub

Here region is the region where the lambda to call resides.

Now lets add a function to call our second lambda

	function callLambdaFunction(query, callback) {
	var params = {
	FunctionName: 'HelloWorld', // the lambda function we are going to invoke
	InvocationType: 'RequestResponse',
	Payload: query
	};
	lambda.invoke(params, function (err, data) {
	if (err) {
	console.log("Error - " + err);
	} else {
	callback(data.Payload)
	}
	})
	}

view raw lambda-calling.js hosted with ❤ by GitHub

Here Function name is the name of function to call, InvocationType is RequestResponse for synchronous call and Payload is the data which we need to send.

We now have sdk & function ready, lets call the lambda now,

	var requestData = JSON.stringify('{ "name" : "Parshuram" }');
	callLambdaFunction(requestData, (theResult) => {
	console.log("sent : " + requestData);
	var output = JSON.parse(theResult);
	console.log("received : " + output);
	});

view raw lambda-callmain.js hosted with ❤ by GitHub

This will successfully return the result.

One important point is, the Role which the calling Lambda function use, must have InvokeAsync & invokeFunction rights. Go to IAM dashboard & add these Lambda actions.

Hope this helps.

Happy Coding,
Parshuram