When a service fails, retrying immediately can overwhelm it further. The circuit breaker pattern prevents cascading failures by failing fast when a service is unhealthy.
How It Works
Circuit States:
CLOSED (normal)
↓ failures reach threshold
OPEN (failing fast)
↓ timeout expires
HALF-OPEN (testing)
↓ success → CLOSED
↓ failure → OPEN
Basic Implementation
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Usage Example
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Advanced Implementation
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Metrics and Monitoring
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Fallback Strategies
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Using Libraries
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Best Practices
Configuration:
✓ Set appropriate thresholds for your SLAs
✓ Use volume threshold to avoid false positives
✓ Tune timeout based on recovery time
✓ Monitor state changes
Implementation:
✓ Apply per-service, not globally
✓ Implement meaningful fallbacks
✓ Log state transitions
✓ Expose health endpoints
Avoid:
✗ Opening circuit on all errors
✗ Too short timeout (thrashing)
✗ Ignoring circuit state in responses
✗ Missing fallback strategies
Conclusion
Circuit breakers are essential for resilient distributed systems. They prevent cascading failures by failing fast and giving services time to recover.
Combine with retries, timeouts, and fallbacks for comprehensive fault tolerance.