Circuit Breaker Pattern

Table of Contents

• Overview
• When to Use
• Quick Start
• Reference Guides
• Best Practices

Overview

Implement circuit breaker patterns to prevent cascading failures and provide graceful degradation when dependencies fail.

When to Use

• External API calls
• Microservices communication
• Database connections
• Third-party service integrations
• Preventing cascading failures
• Implementing fallback mechanisms
• Rate limiting protection
• Timeout handling

Quick Start

Minimal working example:

enum CircuitState {
  CLOSED = "CLOSED",
  OPEN = "OPEN",
  HALF_OPEN = "HALF_OPEN",
}

interface CircuitBreakerConfig {
  failureThreshold: number;
  successThreshold: number;
  timeout: number;
  resetTimeout: number;
}

interface CircuitBreakerStats {
  failures: number;
  successes: number;
  consecutiveFailures: number;
  consecutiveSuccesses: number;
  lastFailureTime?: number;
}

class CircuitBreaker {
  private state: CircuitState = CircuitState.CLOSED;
  private stats: CircuitBreakerStats = {
    failures: 0,
// ... (see reference guides for full implementation)

Reference Guides

Detailed implementations in the references/ directory:

Guide	Contents
TypeScript Circuit Breaker	TypeScript Circuit Breaker
Circuit Breaker with Monitoring	Circuit Breaker with Monitoring
Opossum-Style Circuit Breaker (Node.js)	Opossum-Style Circuit Breaker (Node.js)
Python Circuit Breaker	Python Circuit Breaker
Resilience4j-Style (Java)	Resilience4j-Style (Java)

Best Practices

✅ DO

• Use appropriate thresholds for your use case
• Implement fallback mechanisms
• Monitor circuit breaker states
• Set reasonable timeouts
• Use exponential backoff
• Log state transitions
• Alert on frequent trips
• Test circuit breaker behavior
• Use per-dependency breakers
• Implement health checks

❌ DON'T

• Use same breaker for all dependencies
• Set unrealistic thresholds
• Skip fallback implementation
• Ignore open circuit breakers
• Use overly aggressive reset timeouts
• Forget to monitor