Context and Problem
Applications need to handle failures gracefully to maintain availability:
- Repeated failed requests degrade system performance
- Continuous service failures can cause cascading outages
- Slow responses from dependent services impact user experience
Solution
The Circuit Breaker pattern detects failures and temporarily blocks calls to failing services:
- Monitor service failures based on timeout, errors, or slow responses
- If failures exceed a threshold, the circuit breaker moves to an open state
- Requests to the failing service are blocked for a cooldown period
- After recovery, the circuit breaker allows limited requests before fully reopening
Benefits
- Failure Containment
- Prevents cascading failures across the system
- Improved Stability
- Allows services to recover instead of being overloaded
- Automatic Recovery
- Gradual reintroduction of traffic prevents sudden overload
Trade-offs
- Temporary Downtime
- Blocks service requests while the breaker is open
- Configuration Complexity
- Requires fine-tuning failure thresholds and retry logic
- Monitoring Requirements
- Needs observability to track breaker states
Issues and Considerations
- Threshold Tuning
- Setting appropriate limits to avoid unnecessary blocking
- Service Dependencies
- Ensuring alternative paths exist when services fail
- Performance Impact
- Overhead of monitoring requests and tracking failures
When to Use This Pattern
- Your application depends on external or unstable services
- You need to prevent cascading failures in a microservices environment
- Failures should be handled gracefully without overloading recovery services