In distributed systems, failures are not rare.
They are expected.
If one service fails and others keep calling it:
- System slowdown
- Cascading failures
- Complete outage
The solution?
Circuit Breaker Pattern
What is Circuit Breaker?
Inspired by electrical systems
A circuit breaker stops calls to a failing service to prevent system-wide damage.
Instead of:
Service A → Service B (failing again & again)
You get:
Service A → Circuit Breaker → Stop calls → Recover later
Why It Matters
Without Circuit Breaker:
- Continuous retries
- Resource exhaustion
- System crash
With Circuit Breaker:
- Prevents cascading failures
- Saves system resources
- Improves resilience
- Enables graceful recovery
Three States of Circuit Breaker
1️⃣ Closed (Normal State)
- Requests pass through
- System working fine
2️⃣ Open (Failure State)
- Requests blocked
- No calls to failing service
3️⃣ Half-Open (Testing State)
- Few requests allowed
- Check if service recovered
Example Flow
- Service starts failing
- Circuit opens (stop requests)
- After timeout → half-open
- If success → close circuit
- If failure → open again
Example (Node.js Concept)
circuit = "OPEN"
}
if (circuit === "OPEN") {
return "Service unavailable"
}
Real-World Use Cases
- Payment systems
- External APIs
- Microservices communication
- Third-party integrations
Common Mistakes
- No timeout strategy
- Aggressive retries
- No fallback response
- Ignoring monitoring
Best Practices
- Use fallback responses
- Monitor failure rates
- Combine with retry + timeout
- Use libraries (Hystrix, Resilience4j)
Final Thoughts
Distributed systems are fragile by default.
Circuit Breaker makes them:
- Resilient
- Stable
- Fault-tolerant
If you don’t handle failures:
- Failures will handle your system.
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