Deploy Lambda with API Gateway S3 and Dynamo DB AWS-CDK Part-4

By tkssharma on March 09, 2023

Deploy Lambda with API Gateway S3 and Dynamo DB

Part	Link
Part-0	https://tkssharma.com/aws-cdk-for-deploying-aws-resources-blogs-series
Part-1	https://tkssharma.com/build-and-deploy-application-using-aws-cdk-part-1
Part-2	https://tkssharma.com/build-and-deploy-application-using-aws-cdk-part-2
Part-3	https://tkssharma.com/deploy-api-gateway-using-aws-cdk-part-3

In this Blog we will cover all these Topics

Build a simple Lambda function
Attach REST API gateway to the lambda
Add S3 bucket in our stack
Add Dynamo DB table in out stack
All lambda to access S3 and Dynamo DB
Attaching Lambda to REST API gateway Resource
Deploying and Cleaning up Resources

This is how our whole stack Looks like, lets take a look and understand each and every blocks for these constructs in out Stack

import * as cdk from 'aws-cdk-lib';
import { Construct } from 'constructs';
import { NodejsFunction } from 'aws-cdk-lib/aws-lambda-nodejs';
import * as lambda from 'aws-cdk-lib/aws-lambda';
import * as dynamodb from 'aws-cdk-lib/aws-dynamodb';

import * as path from 'path';

export interface LambdaProps extends cdk.StackProps {
  stage: string;
}

export class LambdaAppStack extends cdk.Stack {
  constructor(scope: Construct, id: string, props: LambdaProps) {
    super(scope, id, props);

    const { stage } = props;

    const userUploadsS3Bucket = new cdk.aws_s3.Bucket(this, `user-api-upload-${stage}`, {
      bucketName: `user-api-upload-${stage}`,
      removalPolicy: cdk.RemovalPolicy.DESTROY,
    });

    const userDynamoTable = new dynamodb.Table(this, `users-table-${stage}`, {
      tableName: `api-users-table-${stage}`,
      partitionKey: { name: 'user_id', type: dynamodb.AttributeType.STRING },
      sortKey: { name: 'created_at', type: dynamodb.AttributeType.NUMBER },
      removalPolicy: cdk.RemovalPolicy.DESTROY,
    });

    const apiGetUsersLambdaFn = new cdk.aws_lambda.Function(this, `api-get-user-${stage}`, {
      functionName: `api-get-user-lambda-${stage}`,
      runtime: cdk.aws_lambda.Runtime.NODEJS_16_X,
      memorySize: 1024,
      logRetention: cdk.aws_logs.RetentionDays.FIVE_DAYS,
      environment: {
        stage,
      },
      handler: 'index.handler',
      code: cdk.aws_lambda.Code.fromAsset(path.join(__dirname, '..', 'src')),
      initialPolicy: [
        new cdk.aws_iam.PolicyStatement({
          effect: cdk.aws_iam.Effect.ALLOW,
          actions: ['s3:*'],
          resources: [userUploadsS3Bucket.bucketArn],
        }),
        new cdk.aws_iam.PolicyStatement({
          effect: cdk.aws_iam.Effect.ALLOW,
          actions: ['sns:*'],
          resources: ['*'],
        }),
        new cdk.aws_iam.PolicyStatement({
          effect: cdk.aws_iam.Effect.ALLOW,
          actions: ['dynamodb:*'],
          resources: [userDynamoTable.tableArn],
        }),
      ],
    });

    userDynamoTable.grantReadWriteData(apiGetUsersLambdaFn);
    userUploadsS3Bucket.grantReadWrite(apiGetUsersLambdaFn);

    // API GW
    const apiGw = new cdk.aws_apigateway.LambdaRestApi(this, `users-api-gw`, {
      handler: apiGetUsersLambdaFn,
      deploy: true,
      proxy: true,
      binaryMediaTypes: ['*/*'],
      deployOptions: {
        stageName: stage,
      },
    });

    new cdk.CfnOutput(this, `apiGetUsersLambdaFn`, {
      exportName: `apiGetUsersLambdaFn--arn`,
      value: apiGetUsersLambdaFn.functionArn,
    });

    new cdk.CfnOutput(this, `userDynamoTable`, {
      exportName: `userDynamoTable--arn`,
      value: userDynamoTable.tableArn,
    });
    new cdk.CfnOutput(this, `userUploadsS3Bucket`, {
      exportName: `userUploadsS3Bucket--arn`,
      value: userUploadsS3Bucket.bucketArn,
    });
    new cdk.CfnOutput(this, `user-api-gateway`, {
      exportName: `user-api--gateway-arn`,
      value: apiGw.restApiName,
    });
  }
}

Build a simple Lambda function

Lets build a simple Lambda Function using simple javascript

const apiGetUsersLambdaFn = new cdk.aws_lambda.Function(this, `api-get-user-${stage}`, {
  functionName: `api-get-user-lambda-${stage}`,
  runtime: cdk.aws_lambda.Runtime.NODEJS_16_X,
  memorySize: 1024,
  logRetention: cdk.aws_logs.RetentionDays.FIVE_DAYS,
  environment: {
    stage,
  },
  handler: 'index.handler',
  code: cdk.aws_lambda.Code.fromAsset(path.join(__dirname, '..', 'src')),
  initialPolicy: [
    new cdk.aws_iam.PolicyStatement({
      effect: cdk.aws_iam.Effect.ALLOW,
      actions: ['s3:*'],
      resources: [userUploadsS3Bucket.bucketArn],
    }),
    new cdk.aws_iam.PolicyStatement({
      effect: cdk.aws_iam.Effect.ALLOW,
      actions: ['sns:*'],
      resources: ['*'],
    }),
    new cdk.aws_iam.PolicyStatement({
      effect: cdk.aws_iam.Effect.ALLOW,
      actions: ['dynamodb:*'],
      resources: [userDynamoTable.tableArn],
    }),
  ],
});

This is how we generally create lambda function in javascript as it does not require compilation Simple Lambda Function with just hello world message Lets see what all we are passing to Lambda Construct

We create a Lambda function called lambdaNode Running on Node.js 14 with 1GB of memory allocated. The timeout is set to 300 seconds which is equal to 5 minutes. The property code indicates the folder's path to find the code to run when the Lambda is triggered. It is located in the src folder at the project root but, it doesn't exist yet,, so let's create it with mkdir src. The handler property indicates the entry file then the function to run inside this file. So the index.handler can be broken down to:

index: the file called index.js inside the src directory.
handler: the function inside the index.js to executes.
logRetention it will enable cloudwatch logs and passed arguments will set the number of days till these logs will be available
environment we can pass key value pair which we need as env variable for this node js Lambda
runtime runtime decided what platform we need for this lambda function like node js, python, java
code we can point to a simple one javascript file or a zip file having handler code in some root level index.js file
initialPolicy we can define policy for this lambda to define its permissions that this lambda can access

How we define policy for lambda

Create a Lambda function.
Create an IAM Policy statement.
Attach an inline policy to the function's role, passing it the policy statement we created.
attach policy to access S3, SNS, SQS or Dynamo Table

[
  new cdk.aws_iam.PolicyStatement({
    effect: cdk.aws_iam.Effect.ALLOW,
    actions: ['s3:*'],
    resources: [userUploadsS3Bucket.bucketArn],
  }),
  new cdk.aws_iam.PolicyStatement({
    effect: cdk.aws_iam.Effect.ALLOW,
    actions: ['sns:*'],
    resources: ['*'],
  }),
  new cdk.aws_iam.PolicyStatement({
    effect: cdk.aws_iam.Effect.ALLOW,
    actions: ['dynamodb:*'],
    resources: [userDynamoTable.tableArn],
  }),
];

This will add policy document for all resources, example of default policy document shown here

{
  "Version": "2012-10-17",
  "Statement": [
    {
      "Effect": "Allow",
      "Action": ["logs:CreateLogGroup", "logs:CreateLogStream", "logs:PutLogEvents"],
      "Resource": "*"
    }
  ]
}

Add S3 bucket and Dynamo DB Table in our stack

const userUploadsS3Bucket = new cdk.aws_s3.Bucket(this, `user-api-upload-${stage}`, {
  bucketName: `user-api-upload-${stage}`,
  removalPolicy: cdk.RemovalPolicy.DESTROY,
});

const userDynamoTable = new dynamodb.Table(this, `users-table-${stage}`, {
  tableName: `api-users-table-${stage}`,
  partitionKey: { name: 'user_id', type: dynamodb.AttributeType.STRING },
  sortKey: { name: 'created_at', type: dynamodb.AttributeType.NUMBER },
  removalPolicy: cdk.RemovalPolicy.DESTROY,
});

Add permission to Read Write Table

userDynamoTable.grantReadWriteData(apiGetUsersLambdaFn);
userUploadsS3Bucket.grantReadWrite(apiGetUsersLambdaFn);

Inside the src folder, create a file called index.js and add the content below:

exports.handler = async function(event) {
  return {
    statusCode: 200,
    headers: { 'Content-Type': 'text/json' },
    body: JSON.stringify({ message: 'Hello from my Lambda node!' }),
  };
};

Attach Proxy REST API Gateway to the lambda

There are many ways in which we can create API gateway

a simple api gateway which is working just a Proxy so all request from gateway will be handled by a one single lambda proxy: true, added here so this will just forward all HTTP requests to this lambda

// API GW
const apiGw = new cdk.aws_apigateway.LambdaRestApi(this, `hello-world-gw`, {
  handler: apiGetUsersLambdaFn,
  deploy: true,
  proxy: true,
  binaryMediaTypes: ['*/*'],
  deployOptions: {
    stageName: stage,
  },
});

we can also print all these resource output

new cdk.CfnOutput(this, `apiGetUsersLambdaFn`, {
  exportName: `apiGetUsersLambdaFn--arn`,
  value: apiGetUsersLambdaFn.functionArn,
});

new cdk.CfnOutput(this, `userDynamoTable`, {
  exportName: `userDynamoTable--arn`,
  value: userDynamoTable.tableArn,
});
new cdk.CfnOutput(this, `userUploadsS3Bucket`, {
  exportName: `userUploadsS3Bucket--arn`,
  value: userUploadsS3Bucket.bucketArn,
});
new cdk.CfnOutput(this, `user-api-gateway`, {
  exportName: `user-api--gateway-arn`,
  value: apiGw.restApiName,
});

Deploy Typescript Lambda to AWS with API Gateway, S3, Dynamo Table

cdk synth
cdk bootstrap
cdk deploy
cdk destroy

When we synthesize our CloudFormation stack, it gets generated in the cdk.out directory. This is also where the asset files for our Lambda functions are stored. Let's run the synth command to generate the lambda assets:

npx aws-cdk synth

If we now take a look at the assets folder in the cdk.out directory, we can see that our Lambda function's code has been compiled down to JavaScript.

Deploy the Lambda function

The next step is to bootstrap an environment. This action is required only if it is the first time you want to deploy with the CDK; you can skip this if you have already done it before.

This command will create a stack that includes resources used for the toolkit's operation, like an S3 bucket to store templates and assets during the deployment process.

cdk bootstrap

⏳  Bootstrapping environment aws://123456789012/eu-west-1...
Once done, we can deploy our app:
``

```sh
npx aws-cdk deploy

Cleanup

To delete the stack from your account, run the destroy command:

npx aws-cdk destroy