Lessons

Setting Up SNS Dead Letter Queues

Introduction

In this lesson, we will learn how to set up SNS Dead Letter Queues (DLQ) to handle messages that cannot be successfully processed by the subscriber. Dead Letter Queues are essential for ensuring message delivery reliability in distributed systems. We will explore how to configure SNS topics with DLQs using AWS services and infrastructure deployment tools like AWS CDK with Typescript.

Prerequisites

Before we begin, make sure you have the following prerequisites:

  • An AWS account with permissions to create SNS topics and SQS queues
  • Basic knowledge of AWS services like SNS, SQS, and IAM
  • Node.js and npm installed on your local machine for using AWS CDK with Typescript

Setting Up SNS Dead Letter Queues with AWS CLI

Step 1: Create an SNS Topic

First, let’s create an SNS topic using the AWS CLI:

aws sns create-topic --name MySNSTopic

Step 2: Create an SQS Queue for Dead Letter Messages

Next, create an SQS queue to serve as the Dead Letter Queue for the SNS topic:

aws sqs create-queue --queue-name MyDLQ

Step 3: Configure the SNS Topic with DLQ

Now, configure the SNS topic to use the SQS queue as the Dead Letter Queue:

aws sns set-topic-attributes --topic-arn arn:aws:sns:us-east-1:123456789012:MySNSTopic --attribute-name RedrivePolicy --attribute-value "{\"deadLetterTargetArn\":\"arn:aws:sqs:us-east-1:123456789012:MyDLQ\",\"maxReceiveCount\":\"5\"}"

Setting Up SNS Dead Letter Queues with AWS CDK and Typescript

Step 1: Install AWS CDK

If you haven’t already, install the AWS CDK CLI globally on your machine:

npm install -g aws-cdk

Step 2: Create a new CDK project

Create a new CDK project using the following command:

cdk init app --language typescript

Step 3: Define the SNS Topic and DLQ in your CDK stack

In your CDK stack file (e.g., MyStack.ts), define the SNS topic and DLQ:

import * as sns from '@aws-cdk/aws-sns';
import * as sqs from '@aws-cdk/aws-sqs';

const topic = new sns.Topic(this, 'MySNSTopic');

const dlq = new sqs.Queue(this, 'MyDLQ', {
  visibilityTimeout: Duration.seconds(300),
});

topic.addSubscription(new subs.SqsSubscription(dlq));

Step 4: Deploy the CDK stack

Deploy the CDK stack to create the SNS topic and DLQ resources in your AWS account:

cdk deploy

Conclusion

In this lesson, we have learned how to set up SNS Dead Letter Queues using both AWS CLI commands and AWS CDK with Typescript. Dead Letter Queues are crucial for handling messages that cannot be processed by subscribers, ensuring message delivery reliability in distributed systems. By following the practical examples provided in this lesson, you can easily configure SNS topics with DLQs in your AWS environment.

Key learnings:

  • Creating an SNS topic and SQS queue using AWS CLI
  • Configuring an SNS topic with a Dead Letter Queue using AWS CLI
  • Defining SNS topic and DLQ resources in a CDK stack using Typescript
  • Deploying the CDK stack to create SNS topic and DLQ resources in AWS

Now, you are ready to implement SNS Dead Letter Queues in your own AWS projects with confidence. Happy coding!

Share :