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.

Review and execute a lambda function deployed with CDK in AWS Console

Let's go to the AWS management console, search for Cloudformation, click on Stacks and check out what we've deployed.

Under the Resources we can see:

• AWS::IAM::Role
• AWS::Lambda::Function
• AWS::CDK::Metadata

Click on the lambda function id to explore it. You'll be able to use the entire code, which starts with use strict and finishes with the source map (because this code was transpiled from typescript).

Further down the page, you'll see Tags associated with this function (those were added automatically).

We currently don't have any Triggers so click on Test and Configure test event to test it manually. Choose Api Gateway AWS Proxy. Name the test then click Create.

Once you click Test again the lambda function will be called and you should see the console.log with "Hello, nothanii friends!" (or your own text).

Resources

• constructs/packages
  • AWS management console
  • Api Gateway AWS Proxy