Create and deploy a lambda function with AWS CDK

Time to build our serverless backend!

We'll be writing our first lambda function. In order to do that, let's run:

• npm install --save @aws-cdk/aws-lambda

Since we are using typescript we'll also:

• npm install --save @types/aws-lambda

👍 We needed to install aws-lambda separately because it's not part of the core aws package. See which other constructs/packages are available in CDK here.

Inside our todo-app will create a new directory called lambda and inside of it, a hello.ts file with the following contents.

// we are going to call this function via APIGatewayEvent which is used for http requests
exports.handler = async function(event: AWSLambda.APIGatewayEvent) {
    // this is a neat trick to prettify the console log
    console.log("request:", JSON.stringify(event, null, 2));

    // this is what calling this lambda function will return
    return {
        statusCode: 200,
        headers: { "Content-Type": "text/plain" },
        body: `Hello, nothanii friends!`
    };
};

We need to import the lambda function into our stack file:

• import * as lambda from "@aws-cdk/aws-lambda";

Then we'll create an instance of our lambda construct, with three arguments:

1. scope (in which the construct is created): usually this
2. id
3. props objects (code, handler and runtime are obligatory)

const helloLambda = new lambda.Function(this, "HelloLambda", {
  // where our code is located (inside the lambda directory)
    code: lambda.Code.fromAsset("lambda"),
    // the function executed whenever this lambda function is triggered (the handler function inside hello.ts file)
    handler: "hello.handler",
    // most recent node
    runtime: lambda.Runtime.NODEJS_12_X,
});

Run cdk diff to see the two new resources:

Resources
[+] AWS::IAM::Role HelloLambda/ServiceRole
[+] AWS::Lambda::Function HelloLambda

Then cdk deploy

👍 Note, if you get the following error (I did): Error: This stack uses assets, so the toolkit stack must be deployed to the environment, run cdk bootstrap to finish configuring your account and avoid this error in the future.

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