/sns-sqs-nodejs-eda

Primary LanguageJavaScript

Event-Driven Architecture using SNS/SQS and Node.js microservices

Goal

The goal of this repository is to provide a minimal example of how two Node.js microservices can communicate with each other using SNS and SQS and try it locally using localstack.

Architecture

Architecture

There are two Node.js services:

  • service A
  • service B

Service A publishes an event to a SNS topic. There are 2 SQS queues, one for each service. Each of these 2 queues is subscribed to the SNS topic service A is publishing to, which means they both receive the events that are published on the topic.

In this example, only service B actually implements the SQS client and cares about the messages published on its queue.

Benefits

  • Both services are fully decoupled: service A doesn't even know about the existence of service B, yet it can communicate with it
  • Using queues make our application resilient: if one of the services goes down, the messages go to the queue and get processed as soon as the service gets back online

Run this locally with localstack

  1. Install localstack
  2. Run ./deploy-localstack.sh to deploy the services to localstack. This will deploy the cloudformation template in infra.yml.
  3. Once this is done, run service B in a terminal: node ./services/B/src/index.js.

Service B will be waiting for messages to be published to the topic by service A.

  1. To publish a message to SNS from service A, run in another terminal: node ./services/A/src/index.js

Now you should see in the first terminal that service B received an event.

[*] Event received: {
  id: '62d2b85b-b3e1-44b2-a7cc-e215c92fc97c',
  publishedAt: '2023-08-08T20:21:56.808Z',
  type: 'MY_EVENT',
  payload: { entityId: '123' }
}

You can destroy the stack that was created by running ./destroy-localstack.sh