Microservices With NestJS, Kafka, and TypeScript

A microservices architecture is a popular software design pattern that enables developers to build and maintain large and complex applications more efficiently. In a microservices architecture, an extensive application is divided into small, independent services that can be developed, tested, and deployed independently.

Why are microservices beneficial to development teams? Well, they empower greater flexibility, independent scalability, and simplified maintenance. You know, the things that teams need to stay agile.

What’s also crucial? Due to the fact that microservices are broken out into smaller containers, troubleshooting issues is a breeze when compared to their monolithic predecessors. Basically: If an issue arises with one service, it can be fixed in isolation with little disturbance to the rest of the infrastructure. Downtime clock? We’ll stop you right there.

So, what tools and technologies can be used to build microservices? Just pick your poison. One service could be created using Node.js, and another could be built with Java, so on and so forth. It’s up to your development team to work within the technologies they are most comfortable with. And why not embrace the specialized expertise already on the team?

Here are a few different ways to kickstart your journey using NestJS, Kafka, and TypeScript.

Getting Started With NestJS and TypeScript

NestJS is a framework for building efficient, scalable, and modular server-side applications with TypeScript. It’s built on top of Express, a popular Node.js web framework, which uses the power of TypeScript to provide a seamless development experience. Helpful indeed.

To get started with NestJS, you must have Node.js and TypeScript installed on your machine. You can then create a new NestJS project using the Nest CLI, which can be installed using npm:

npm install -g @nestjs/cli

Once the Nest CLI is installed, you can create a new project using the following command:

nest new my-project

This will create a new directory called my-project with the basic structure of a NestJS application. The project structure will look something like this:

my-project
├── src
│   ├── app.module.ts
│   ├── app.controller.ts
│   ├── app.service.ts
│   └── main.ts
├── test
│   ├── app.e2e-spec.ts
│   └── jest-e2e.json
├── .gitignore
├── nest-cli.json
├── package.json
└── README.md

You’ll notice that the main entry point for the application is main.ts, which bootstraps the NestJS application and starts the server. Also, the app.module.ts file defines the application’s root module and lists the imported modules and controllers. Additionally, the app.controller.ts file defines a simple controller that handles HTTP requests. And finally (hopefully with a breath in between), the app.service.ts file defines a service that the controller can use to perform the action. That’s a lot, but it’s very useful for teams.

To run the application, use the following command:

npm run start

This will compile the TypeScript code and start the server. You can then access the application at http://localhost:3000.

NestJS provides a range of features and decorators that make it easy to build robust and scalable server-side applications with TypeScript. For example, you can use the @Controller and @Get decorators to define a simple RESTful API like this:

import { Controller, Get } from "@nestjs/common";

@Controller("users")
export class UsersController {
  @Get()
  findAll() {
    return "This action returns all users";
  }
}

You can also use the @Module decorator to define a module that encapsulates a group of related controllers, services, and providers. Think of this as a good way to keep your code organized and to promote code reuse.

In summary, NestJS is a robust framework for building efficient, scalable, and modular server-side applications with TypeScript. Its decorators and modular architecture make building and maintaining complex applications a light lift. Its strong integration with Express and other popular Node.js libraries is why it’s an excellent choice for building microservices with TypeScript.

Integrating Kafka for Event-Driven Communication

Kafka is a distributed streaming platform that is often used in microservices architectures to enable event-driven communication between services. Why is it so useful to developers? In a microservices architecture, services may need to communicate with each other to share data or trigger specific actions. Kafka provides a messaging system that allows services to publish and subscribe to streams of records called topics. Here’s how to get going:

To use Kafka in a NestJS application, you will need to install the @nestjs/microservices package, which provides a client for the Kafka protocol:

npm install @nestjs/microservices

Once the package is installed, you can create a new Kafka client using the KafkaClient class:

import { KafkaClient } from "@nestjs/microservices";

const client = new KafkaClient({
  brokers: ["kafka1:9092", "kafka2:9092"],
});

The KafkaClient class takes an options object with a list of broker addresses as the argument. You can then use the client to connect to a Kafka cluster and publish or subscribe to topics.

To publish a message to a topic, you can use the send method of the client:

await client.send({
  topic: "users",
  messages: [{ value: JSON.stringify({ id: 1, name: "John" }) }],
});

To subscribe to a topic, you can use the subscribe method and provide a callback function to handle incoming messages:

client.subscribe("users", async (message: any) => {
  console.log(`Received message: ${message.value}`);
});

In addition to the KafkaClient class, the @nestjs/microservices package also provides a KafkaServer class, which allows you to create a Kafka server that listens for incoming messages on a specific topic. Harness this class to create a Kafka server that acts as a bridge between your NestJS application and other Kafka clients. Here’s the code you need:

import { KafkaServer } from "@nestjs/microservices";

const server = new KafkaServer({
  client: client,
  options: {
    groupId: "my-group",
    id: "kafka-server",
  },
});

Okay, now that you’ve tried that. Let’s keep going.

It’s important to remember that the KafkaServer class takes an options object with a client property that specifies the Kafka client to use. It also takes an options property that specifies the group ID and server ID. After, you can then use the bindHandler method to bind a handler function to a specific topic. Like this:

server.bindHandler("users", async (message: any) => {
  console.log(`Received message: ${message.value}`);
});

Hopefully that’s working for you, and your communication between servers is crystal clear.

In summary, Kafka is a powerful tool enabling event-driven communication between microservices in a NestJS application. With Kafka, you can publish and subscribe to streams of records and create a flexible and scalable messaging system for your microservices architecture. The @nestjs/microservices package provides a convenient client and server implementation that makes it easy to integrate Kafka into your NestJS application. Take advantage.

Advanced Features of NestJS for Building Microservices

When it comes to NestJS, there’s always more to untap.

In fact, NestJS provides a range of advanced features that can be used to build robust and scalable microservices. Let’s explore these features in more detail.

One helpful feature of NestJS is the ability to use pipes to transform incoming request data. Pipes are functions that can modify request data before it is passed to a controller action. For example, you can use a pipe to validate incoming data, transform data from one format to another, or perform another operation on the data. Pretty neat.

To create a pipe, you can use the @Injectable() decorator and the PipeTransform interface:

import { Injectable, PipeTransform } from "@nestjs/common";

@Injectable()
export class ValidationPipe implements PipeTransform {
  transform(value: any) {
    // Validate and transform the value here
  }
}

Once you’ve entered that code, you can then use the pipe by applying the @UsePipes() decorator to a controller action:

import { Controller, Get, UsePipes } from "@nestjs/common";
import { ValidationPipe } from "./validation.pipe";

@Controller("users")
export class UsersController {
  @Get()
  @UsePipes(new ValidationPipe())
  findAll() {
    // The value passed to the controller action has been validated and transformed
  }
}

It doesn’t end there. Another valuable feature of NestJS is the ability to use guards to protect routes. Guards are functions that can be used to check the request context and determine whether a user is authorized to access a route. Use a guard to check if a user is authenticated before allowing them through—it’s a handy little security tool.

Want to create a guard? Use the @Injectable() decorator and the CanActivate interface:

import { Injectable, CanActivate } from "@nestjs/common";

@Injectable()
export class AuthGuard implements CanActivate {
  canActivate() {
    // Check the request context and return true if the user is authorized
  }
}

Next, you can use the guard by applying the @UseGuards() decorator to a controller action:

import { Controller, Get, UseGuards } from "@nestjs/common";
import { AuthGuard } from "./auth.guard";

@Controller("users")
export class UsersController {
  @Get()
  @UseGuards(AuthGuard)
  findAll() {
    // The route is protected by the AuthGuard
  }
}

It doesn’t stop with pipes and guards. NestJS also provides a range of other advanced features for building microservices. This includes interceptors for modifying request and response objects, providers for injecting dependencies into controllers and services, and decorators for defining custom routing and controller logic.

We can keep going, but I’m sure you’ve got some coding to finish up before you call it a day.

Best Practices for Managing a Microservices Architecture with NestJS and Kafka

When managing a microservices architecture with NestJS and Kafka, it is essential to follow best practices. You need to ensure that your system is efficient, scalable, and easy to maintain.

Always double check that the services are decoupled and independent from one another. This will make development, testing, and deployment easier to manage down the road.

Establish that services are self-contained. You should include all the resources needed to perform a specific task within a single service. This shouldn’t be limited to data stores, libraries, and other dependencies. After all, keeping services self-contained can reduce the risk of dependencies breaking.

Are your services loosely coupled as well? This is an important rule of thumb. You definitely want to avoid direct dependencies between services and rely on message-based communication. Kafka is a powerful tool for achieving this, as it allows services to publish and subscribe to streams of records.

Another critical aspect of managing a microservices architecture is confirming that services can handle a high volume of requests. Be sure to design services that are stateless and horizontally scalable. Stateless services do not store state within the service itself and rely on external stores for data persistence. This makes it easier to scale horizontally by adding additional instances. Consider using load balancers and other tools to distribute traffic across multiple instances of a service. This will improve performance and reliability as a whole.

Finally, constantly consider the specific needs of your application when designing and managing a microservices architecture. Do this until you’re blue in the face. You’ve got this!

If you’re interested in building microservices with NestJS and Kafka, many resources are available online, including documentation, tutorials, and case studies. Consider joining a community of developers and experts working with these technologies, such as online forums or meetups. By staying up-to-date with the latest developments and best practices, you can continue to improve your skills and build more effective microservices with NestJS and Kafka. At Split, we’re always here to help you along your journey to best practices.