Resilience4j usage

1. pom

1) normal

        <dependency>
            <groupId>io.github.resilience4j</groupId>
            <artifactId>resilience4j-circuitbreaker</artifactId>
            <version>0.13.2</version>
        </dependency>
        <dependency>
            <groupId>io.github.resilience4j</groupId>
            <artifactId>resilience4j-retry</artifactId>
            <version>0.13.2</version>
        </dependency>

2) spring boot

        <dependency>
            <groupId>io.github.resilience4j</groupId>
            <artifactId>resilience4j-spring-boot</artifactId>
            <version>0.13.2</version>
        </dependency>
        <dependency>
            <groupId>io.github.resilience4j</groupId>
            <artifactId>resilience4j-retry</artifactId>
            <version>0.13.2</version>
        </dependency>

3) spring boot2

        <dependency>
            <groupId>io.github.resilience4j</groupId>
            <artifactId>resilience4j-spring-boot2</artifactId>
            <version>0.13.2</version>
        </dependency>
        <dependency>
            <groupId>io.github.resilience4j</groupId>
            <artifactId>resilience4j-retry</artifactId>
            <version>0.13.2</version>
        </dependency>

2. create CB

1) CircuitBreakerRegistry

（1）default

CircuitBreakerRegistry circuitBreakerRegistry = CircuitBreakerRegistry.ofDefaults();

// Get a CircuitBreaker from the CircuitBreakerRegistry with the global default configuration
CircuitBreaker circuitBreaker2 = circuitBreakerRegistry.circuitBreaker("myCB2");

（2）custom

// Create a custom configuration for a CircuitBreaker
CircuitBreakerConfig circuitBreakerConfig = CircuitBreakerConfig.custom()
    .failureRateThreshold(50)
    .waitDurationInOpenState(Duration.ofMillis(1000))
    .ringBufferSizeInHalfOpenState(2)
    .ringBufferSizeInClosedState(2)
    .build();

// Create a CircuitBreakerRegistry with a custom global configuration
CircuitBreakerRegistry circuitBreakerRegistry = CircuitBreakerRegistry.of(circuitBreakerConfig);


// Get a CircuitBreaker from the CircuitBreakerRegistry with a custom configuration
CircuitBreaker circuitBreaker = circuitBreakerRegistry.circuitBreaker("myCB1", circuitBreakerConfig);

2) directly

(1) default

CircuitBreaker defaultCircuitBreaker = CircuitBreaker.ofDefaults("myCB2");

// Create a Retry with at most 3 retries and a fixed time interval between retries of 500ms
Retry retry = Retry.ofDefaults("myCB2");

(2) custom

// Create a custom configuration for a CircuitBreaker
CircuitBreakerConfig circuitBreakerConfig = CircuitBreakerConfig.custom()
    .failureRateThreshold(50)
    .waitDurationInOpenState(Duration.ofMillis(1000))
    .ringBufferSizeInHalfOpenState(2)
    .ringBufferSizeInClosedState(2)
    .build();

CircuitBreaker customCircuitBreaker = CircuitBreaker.of("myCB1", circuitBreakerConfig);

// Create a Retry with at most 3 retries and a fixed time interval between retries of 500ms
Retry retry = Retry.ofDefaults("myCB1");

3. decorate

1) backend

// Simulates a Backend Service
public interface BackendService {
    String doSomething();
}

2) Attached

// Decorate your call to BackendService.doSomething() with a CircuitBreaker
Supplier<String> decoratedSupplier = CircuitBreaker
    .decorateSupplier(circuitBreaker, backendService::doSomething);

// Decorate your call with automatic retry
decoratedSupplier = Retry
    .decorateSupplier(retry, decoratedSupplier);

3. Exec

1) vavr

// Execute the decorated supplier and recover from any exception
String result = Try.ofSupplier(decoratedSupplier)
    .recover(throwable -> "Hello from Recovery").get();

System.out.println(result);

2) lambda expression

// When you don't want to decorate your lambda expression,
// but just execute it and protect the call by a CircuitBreaker.
String result = circuitBreaker.executeSupplier(backendService::doSomething);

System.out.println(result);

Reference:

    1. Achieving Fault Tolerance With Resilience4j

    2. resilience4j - circuit breaker