Deploy a lambda function written in typescript using cdktf and esbuild

Table of contents

Goal

Goal behind this blog, is to deploy a lambda function in aws written in typescript using cdktf and esbuild and make that lambda function invocable from internet.

Prerequisite

I assume you have

• Basic typescript knowledge
• git, node, npm and terraform cli installed
• aws account and cli installed and configured with access_key_id and access_key_secret

Setup

Clone the repo nivekithan/blog-deploy-typescript-lambda

git clone https://github.com/nivekithan/blog-deploy-typescript-lambda.git lambda-cdktf
cd lambda-cdktf

Familiarizing with the ts-lambda source code

If you see the code you will find two directories named cdktf and ts-lambda. ts-lambda contains source code for our lambda function and cdktf contains source for managing our infrastructure.

Our lambda function in ts-lambda/src/index.ts is fairly simple

export const handler = async () => {
  return {
    statusCode: 200,
    headers: {
      "Content-Type": "text/html; charset=utf-8",
    },
    body: `<h1>Hello World, This is written in typescript</h1>`,
  };
};

It exports a handler function which when called will return following html

<h1>Hello World, This is written in typescript</h1>

Deploying our application

We are not actually intreseted in what does our lambda function does. We are only intreseted in deploying that lambda function. So lets look into cdktf directory.

First lets see contents of package.json

// cdktf/package.json

{
  "name": "cdktf",
  "version": "1.0.0",
  "description": "",
  "keywords": [],
  "author": "",
  "license": "MIT",
  "dependencies": {
    "@cdktf/provider-aws": "^9.0.51",
    "cdktf": "^0.12.3",
    "constructs": "^10.1.123",
    "esbuild": "^0.15.10"
  },
  "devDependencies": {
    "@types/node": "^18.8.0"
  }
}

• cdktf package allows us to manage our infrastructure in typescript instead of HCL
• @cdktf/provider-aws package is used to provision and manage aws infrastructure
• constructs package is used to create reusable cloud resource
• esbuild package is used to compile typescript to javascript and bundle it to single file.

Lets take a look at main.ts

import { Construct } from "constructs";
import { App, TerraformOutput, TerraformStack } from "cdktf";
import * as aws from "@cdktf/provider-aws";
import path from "node:path";
import { TypescriptFunction } from "./lib/typescriptFunction";

const lambdaRolePolicy = {
  Version: "2012-10-17",
  Statement: [
    {
      Action: "sts:AssumeRole",
      Principal: {
        Service: "lambda.amazonaws.com",
      },
      Effect: "Allow",
      Sid: "",
    },
  ],
};

export type LambdaConfig = {
  /**
   * Absolute path to directory which contains src/index.js which then exports handler
   * function
   */
  path: string;

  /**
   * Lambda version
   */
  version: string;
};

class LambdaStack extends TerraformStack {
  constructor(scope: Construct, name: string, config: LambdaConfig) {
    super(scope, name);

    new aws.AwsProvider(this, "aws", {
      region: "ap-south-1",
    });

    const sourceCodeAsset = new TypescriptFunction(this, "lambda-source-code", {
      absPath: config.path,
      handler: "index.handler",
    });

    // Create a s3 bucket
    const bucket = new aws.s3.S3Bucket(this, "bucket", {
      bucketPrefix: "slack-search-lambda",
    });

    // Upload source code to s3
    const lambdaArchive = new aws.s3.S3Object(this, "lambda-archive", {
      bucket: bucket.bucket,
      key: `${sourceCodeAsset.asset.fileName}/${config.version}`,
      source: sourceCodeAsset.asset.path,
    });

    // Create lambda role

    const role = new aws.iam.IamRole(this, "lambda-exec", {
      name: `learn-cdktf-${name}`,
      assumeRolePolicy: JSON.stringify(lambdaRolePolicy),
    });

    new aws.iam.IamRolePolicyAttachment(this, "lambda-managed-policy", {
      policyArn:
        "arn:aws:iam::aws:policy/service-role/AWSLambdaBasicExecutionRole",
      role: role.name,
    });

    const lambdaFunc = new aws.lambdafunction.LambdaFunction(
      this,
      "slack-search-lambda",
      {
        functionName: `slack-search-lambda`,
        s3Bucket: bucket.bucket,
        s3Key: lambdaArchive.key,
        handler: "index.handler",
        runtime: "nodejs16.x",
        role: role.arn,
      }
    );

    new aws.lambdafunction.LambdaPermission(
      this,
      "lambda-allow-public-access",
      {
        statementId: "FunctionURLAllowPublicAccess",
        principal: "*",
        action: "lambda:InvokeFunctionUrl",
        functionName: lambdaFunc.functionName,
        functionUrlAuthType: "NONE",
      }
    );

    const lambdaFunctionUrl = new aws.lambdafunction.LambdaFunctionUrl(
      this,
      "lambdaFunctionUrl",
      { authorizationType: "NONE", functionName: lambdaFunc.functionName }
    );

    new TerraformOutput(this, "lambda-url", {
      value: lambdaFunctionUrl.functionUrl,
    });
  }
}

const app = new App();

new LambdaStack(app, "cdktf", {
  path: path.resolve(__dirname, "..", "ts-lambda"),
  version: "0.0.5",
});

app.synth();

Deploying to aws

To deploy to aws first we have to install cdktf cli. For that run

pnpm i -g cdktf-cli

## if you prefer npm
npm i -g cdktf-cli

then install all packages in cdktf directory

## lambda-cdktf/cdktf/

pnpm i

## or if you prefer npm
npm i

Now to deploy run

## lambda-cdktf/cdktf
cdktf deploy

Then select Approve and thats it. Once the its deployed you will be able to see the lambda url.

For example, for me it shows

Apply complete! Resources: 7 added, 0 changed, 0 destroyed.
       
Outputs:

    lambda-url = "https://3gcd3p4j4ypvucb5eo4bg3dcgm0dobsb.lambda-url.ap-south-1.on.aws/"

cdktf
lambda-url = https://3gcd3p4j4ypvucb5eo4bg3dcgm0dobsb.lambda-url.ap-south-1.on.aws/

Opening that url in browser shows


Hopefully it shows same for you too. If you face any let me know, I will help you to my best of efforts.

Cleanup

To destroy all the resource created and prevent accidental aws cost run

cdktf destroy