SoFunction
Updated on 2025-04-07

SpringCloud uses CircuitBreaker to implement fuses

Introduction to fuse mode

The core idea of ​​fuse mode isMonitoring service callsstatus. When the failure rate exceeds the threshold, the fuse will enter the "Open" state, and subsequent calls will directly return the preset downgrade result to avoid resource exhaustion. After a period of time, the fuse will try to enter a "half-open" state, allowing some requests to pass to detect whether the downstream service is restored.

Spring Cloud CircuitBreaker

Spring Cloud providesspring-cloud-starter-circuitbreakerAbstract layer, supports multiple implementations (such as Resilience4j, Sentinel). The following isResilience4jAs an example.

Step 1: Add dependencies

existIntroduce dependencies:

<!-- Spring Cloud Circuit Breaker Starter -->
<dependency>
    <groupId></groupId>
    <artifactId>spring-cloud-starter-circuitbreaker-resilience4j</artifactId>
</dependency>
 
<!-- Actuator（Optional，For monitoring） -->
<dependency>
    <groupId></groupId>
    <artifactId>spring-boot-starter-actuator</artifactId>
</dependency>

Step 2: Configure the fuse parameters

existConfigure Resilience4j:

resilience4j:
  circuitbreaker:
    configs:
      default:
        failureRateThreshold: 50     # The failure rate threshold for triggering the circuit breaker (%)        minimumNumberOfCalls: 5       # Minimum number of calls to calculate the failure rate        slidingWindowType: COUNT_BASED # Sliding window type (based on the number of calls)        slidingWindowSize: 10         # Sliding window size        waitDurationInOpenState: 5s   # Waiting time after the fuse is turned on        permittedNumberOfCallsInHalfOpenState: 3 # The number of calls allowed in the half-open state        automaticTransitionFromOpenToHalfOpenEnabled: true # Automatically switch to half-open state

Step 3: Annotation with @CircuitBreaker

Add annotations on the method that needs to be fuse and specify a downgrade method:

import ;
 
@Service
public class UserService {
 
    @Autowired
    private CircuitBreakerFactory circuitBreakerFactory;
 
    public String getUserInfo(String userId) {
        return ("userServiceCircuitBreaker")
            .run(
                () -> {
                    // Actual business logic, such as remote call                    return (userId);
                },
                throwable -> {
                    // downgrade processing                    return "Fallback User Info";
                }
            );
    }
}

Step 4: Define the Fallback method

passfallbackMethodThe attribute specifies the downgrade method:

@CircuitBreaker(name = "userService", fallbackMethod = "getUserFallback")
public User getUser(String userId) {
    // Call remote service}
 
// The method signature must be consistent with the original method, and finally add the Throwable parameterprivate User getUserFallback(String userId, Throwable t) {
    return new User("fallback-user", "Service Unavailable");
}

Step 5: Configure global default values

Customize global default configuration:

@Bean
public CircuitBreakerConfigCustomizer defaultConfig() {
    return config -> config
        .failureRateThreshold(60)
        .waitDurationInOpenState((10));
}

Advanced configuration

1. Combined with Retry mechanism

Try to try again before the circuit breaker:

resilience4j:
  retry:
    configs:
      default:
        maxAttempts: 3
        waitDuration: 500ms

2. Combination of current limiting and fuse

useBulkheadRestrict concurrent calls:

@Bulkhead(name = "userService", type = )
@CircuitBreaker(name = "userService")
public User getUser(String userId) { ... }

Summarize

Through Spring Cloud CircuitBreaker, we can effectively improve the flexibility of microservice architecture. The key is:

  • Correctly configure the fuse parameters

  • Design a reasonable downgrade strategy

  • In combination with the monitoring system, timely discover problems

This is the end of this article about the detailed steps of SpringCloud using CircuitBreaker to implement fuses. For more related SpringCloud CircuitBreaker content, please search for my previous articles or continue browsing the related articles below. I hope everyone will support me in the future!