resilience

name	resilience
description	Resilience4j circuit breaker, retry, rate limiter, and bulkhead patterns with testing strategies. Use when implementing fault tolerance between services.
triggers	["circuit breaker","resilience4j","retry pattern","fallback method","rate limiter","bulkhead pattern","서킷 브레이커","장애 대응"]

1. Resilience4j Configuration

Pattern	Config Key	Default Value	Purpose
Circuit Breaker	failureRateThreshold	50 (%)	Open circuit when 50% of calls fail
Circuit Breaker	slidingWindowSize	10	Number of calls to evaluate
Circuit Breaker	waitDurationInOpenState	10s	Time before half-open
Retry	maxAttempts	3	Total attempts including initial
Retry	waitDuration	500ms	Wait between retries
Rate Limiter	limitForPeriod	100	Max calls per period
Bulkhead	maxConcurrentCalls	25	Max concurrent calls

2. Pattern Application Map

Service Call	Pattern(s)	Fallback
Payment -> External gateway	CircuitBreaker + Retry	Queue for later processing
Order -> Payment service	CircuitBreaker	Accept order, process payment async
Order -> Product service	CircuitBreaker + Retry	Return cached stock status
API Gateway -> any service	Rate Limiter + Bulkhead	429 Too Many Requests

3. Implementation Checklist

• @CircuitBreaker(name = "...", fallbackMethod = "...") on service methods
• @Retry(name = "...") on idempotent operations only
• Fallback method has same signature + Throwable parameter
• Config in application.yml under resilience4j.*
• Actuator endpoints exposed for monitoring (/actuator/circuitbreakers)
• Circuit breaker state changes logged

4. Testing Resilience

• Unit test: mock service to throw exception, verify fallback invoked
• Integration test: stop dependent container, verify circuit opens
• k6 test: measure response time with circuit open vs closed
• Chaos test: kill payment-service container during load test