Implementing Circuit Breaker Pattern for Resilient Microservices

In distributed systems, a single unresponsive service can cascade through your entire architecture. The Circuit Breaker pattern prevents this by failing fast when downstream services struggle.

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Circuit Breaker States

CLOSED (normal) ──failure threshold──► OPEN (fail fast)
    ▲                                      │
    │                                      │
    └───success───── HALF_OPEN ◄───timeout─┘
                      (test)

• CLOSED: Requests pass through normally
• OPEN: Requests fail immediately without calling downstream
• HALF_OPEN: Limited test requests to check recovery

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Resilience4j Configuration

resilience4j:
  circuitbreaker:
    instances:
      paymentService:
        slidingWindowSize: 10
        failureRateThreshold: 50
        waitDurationInOpenState: 10s
        permittedNumberOfCallsInHalfOpenState: 3

slidingWindowSize: calls to evaluate, failureRateThreshold: opens circuit when exceeded, waitDurationInOpenState: time before testing recovery.

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Implementation

@CircuitBreaker(name = "paymentService", fallbackMethod = "fallback")
public PaymentResponse process(PaymentRequest request) {
    return paymentClient.process(request);
}

private PaymentResponse fallback(PaymentRequest request, Exception e) {
    return PaymentResponse.pending("Queued for retry");
}

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Combining with Retry

@CircuitBreaker(name = "paymentService", fallbackMethod = "fallback")
@Retry(name = "paymentService")
public Response process(Request req) {
    return client.call(req);
}

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Use Cases

Circuit breaker is essential for high-availability architectures: e-commerce payments, financial trading, real-time gaming, casino solution platforms, and microservices with external dependencies.

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Tune thresholds per service, always implement fallbacks, and monitor state transitions.

Reference: The Hidden Complexity of Message Queue Architecture