Building Resilient Systems with Circuit Breakers

Introduction to Circuit Breakers

Circuit breakers are a design pattern used to prevent cascading failures in distributed systems. When a service is not responding, a circuit breaker can detect this and prevent further requests from being sent to it, allowing the system to recover. This pattern is essential in microservices architecture and Fintech engineering, where multiple services interact with each other.

How Circuit Breakers Work

A circuit breaker works by monitoring the number of failed requests to a service. If the number of failed requests exceeds a certain threshold, the circuit breaker trips and prevents further requests from being sent to the service. The circuit breaker then enters a half-open state, where it allows a limited number of requests to be sent to the service to test if it has recovered.

Implementing Circuit Breakers in TypeScript

Here is an example of a simple circuit breaker implemented in TypeScript:

class CircuitBreaker {
  private threshold: number;
  private timeout: number;
  private failedRequests: number;
  private halfOpen: boolean;

  constructor(threshold: number, timeout: number) {
    this.threshold = threshold;
    this.timeout = timeout;
    this.failedRequests = 0;
    this.halfOpen = false;
  }

  public async callService(service: () => Promise<any>): Promise<any> {
    if (this.halfOpen) {
      try {
        const result = await service();
        this.halfOpen = false;
        this.failedRequests = 0;
        return result;
      } catch (error) {
        this.halfOpen = true;
        this.failedRequests++;
        throw error;
      }
    }

    if (this.failedRequests >= this.threshold) {
      throw new Error('Circuit breaker tripped');
    }

    try {
      const result = await service();
      return result;
    } catch (error) {
      this.failedRequests++;
      if (this.failedRequests >= this.threshold) {
        this.halfOpen = true;
      }
      throw error;
    }
  }
}

Using Circuit Breakers with Next.js

Next.js provides a built-in way to handle errors using error handling pages. However, when using circuit breakers, it's essential to handle errors explicitly to prevent the circuit breaker from tripping unnecessarily. Here is an example of using a circuit breaker with Next.js:

import { CircuitBreaker } from '../circuit-breaker';

const circuitBreaker = new CircuitBreaker(5, 1000);

export async function getServerSideProps() {
  try {
    const result = await circuitBreaker.callService(async () => {
      const response = await fetch('https://example.com/api/data');
      return response.json();
    });
    return { props: result };
  } catch (error) {
    return { props: {} };
  }
}

Benefits of Circuit Breakers

Circuit breakers provide several benefits, including:

• Preventing cascading failures: By detecting when a service is not responding and preventing further requests from being sent to it, circuit breakers can prevent cascading failures.
• Improving resilience: Circuit breakers can improve the resilience of a system by allowing it to recover from failures.
• Reducing latency: By preventing requests from being sent to a non-responding service, circuit breakers can reduce latency.

Conclusion

In conclusion, circuit breakers are a design pattern that can help prevent cascading failures in distributed systems. By implementing circuit breakers in TypeScript and using them with Next.js, developers can improve the resilience and reliability of their systems. If you're interested in learning more about building resilient systems, contact us to discuss how we can help.