In distributed systems, microservices depend on other external services. If one downstream service experiences slow responses or downtime, calling it repeatedly can saturate connection pools, causing a cascade failure across your entire system.
This guide explains how to implement the Circuit Breaker and Retry patterns in Node.js to keep your systems resilient.
1. The Retry Pattern with Exponential Backoff
When calling an external service, transient network failures are common. Instead of failing immediately, retry the request. Implement Exponential Backoff with jitter to prevent slamming the external server during a recovery window.
2. The Circuit Breaker Pattern
If a downstream service fails repeatedly, the circuit breaker opens, preventing further calls and returning a fallback response immediately.
- Closed State: Requests pass through normally.
- Open State: Downstream calls are blocked, and fallback responses are returned instantly.
- Half-Open State: A small volume of test requests are sent to check if the downstream service has recovered.