Resilience4j Circuit breaker implementation using Spring Boot 2

This is a Spring Boot2 example to demonstrate how we can use Resilience4j in Spring Boot2 Rest Service

Running the app

1- Start the docker compose file

docker-compose up -d

2- Verify the mock rest service

Once the docker-compose up is executed successfully, hit the below url to see if the mock rest service is available

Syntax: http://localhost:5050/{some-message}

Request: http://localhost:5050/something

Response: / - Hello something! Host:b745bed59ddf/172.27.0.2

3- Run the app

./gradlew bootRun

4- Access Swagger UI

Open browser and execute the below url

http://localhost:8080/swagger-ui.html

You can see the swagger ui like as shown below

and when you hit the /hello-world GET service you will a hello world message like as shown

5- Stop the docker compose

docker-compose down

6- Hit the /hello-world GET service in Swagger

Now if you hit the /hello-world GET service in Swagger after stopping the docker compose you will get a message like as shown

7- Hit the /hello-world more than 6 times

If you hit the /hello-world service more than 7 times then Circuit Breaker will be open and further service hitting will be blocked for next 30 seconds. One Sample logs is shown below

2020-07-28 00:07:26.329 ERROR 77427 --- [nio-8080-exec-7] c.s.r.service.HelloWorldGateway          : Inside fallbackForGetSeller, cause - org.springframework.web.client.ResourceAccessException: I/O error on GET request for "http://localhost:5050/world": Connection refused (Connection refused); nested exception is java.net.ConnectException: Connection refused (Connection refused)
2020-07-28 00:07:26.705  INFO 77427 --- [nio-8080-exec-8] c.s.r.service.HelloWorldGateway          : calling getHelloWorld()
2020-07-28 00:07:26.707 ERROR 77427 --- [nio-8080-exec-8] c.s.r.service.HelloWorldGateway          : Inside fallbackForGetSeller, cause - org.springframework.web.client.ResourceAccessException: I/O error on GET request for "http://localhost:5050/world": Connection refused (Connection refused); nested exception is java.net.ConnectException: Connection refused (Connection refused)
2020-07-28 00:07:27.213  INFO 77427 --- [nio-8080-exec-9] c.s.r.service.HelloWorldGateway          : calling getHelloWorld()
2020-07-28 00:07:27.215 ERROR 77427 --- [nio-8080-exec-9] c.s.r.service.HelloWorldGateway          : Inside fallbackForGetSeller, cause - org.springframework.web.client.ResourceAccessException: I/O error on GET request for "http://localhost:5050/world": Connection refused (Connection refused); nested exception is java.net.ConnectException: Connection refused (Connection refused)
2020-07-28 00:07:27.770  INFO 77427 --- [io-8080-exec-10] c.s.r.service.HelloWorldGateway          : calling getHelloWorld()
2020-07-28 00:07:27.773 ERROR 77427 --- [io-8080-exec-10] c.s.r.service.HelloWorldGateway          : Inside fallbackForGetSeller, cause - org.springframework.web.client.ResourceAccessException: I/O error on GET request for "http://localhost:5050/world": Connection refused (Connection refused); nested exception is java.net.ConnectException: Connection refused (Connection refused)
2020-07-28 00:07:28.142  INFO 77427 --- [nio-8080-exec-1] c.s.r.service.HelloWorldGateway          : calling getHelloWorld()
2020-07-28 00:07:28.145 ERROR 77427 --- [nio-8080-exec-1] c.s.r.service.HelloWorldGateway          : Inside fallbackForGetSeller, cause - org.springframework.web.client.ResourceAccessException: I/O error on GET request for "http://localhost:5050/world": Connection refused (Connection refused); nested exception is java.net.ConnectException: Connection refused (Connection refused)
2020-07-28 00:07:28.379  INFO 77427 --- [nio-8080-exec-2] c.s.r.service.HelloWorldGateway          : calling getHelloWorld()
2020-07-28 00:07:28.381 ERROR 77427 --- [nio-8080-exec-2] c.s.r.service.HelloWorldGateway          : Inside fallbackForGetSeller, cause - org.springframework.web.client.ResourceAccessException: I/O error on GET request for "http://localhost:5050/world": Connection refused (Connection refused); nested exception is java.net.ConnectException: Connection refused (Connection refused)
2020-07-28 00:07:28.657  INFO 77427 --- [nio-8080-exec-3] c.s.r.service.HelloWorldGateway          : calling getHelloWorld()
2020-07-28 00:07:28.669 ERROR 77427 --- [nio-8080-exec-3] c.s.r.service.HelloWorldGateway          : Inside fallbackForGetSeller, cause - org.springframework.web.client.ResourceAccessException: I/O error on GET request for "http://localhost:5050/world": Connection refused (Connection refused); nested exception is java.net.ConnectException: Connection refused (Connection refused)
2020-07-28 00:07:28.885 ERROR 77427 --- [nio-8080-exec-5] c.s.r.service.HelloWorldGateway          : Inside fallbackForGetSeller, cause - io.github.resilience4j.circuitbreaker.CallNotPermittedException: CircuitBreaker 'hello-world' is OPEN and does not permit further calls
2020-07-28 00:07:29.080 ERROR 77427 --- [nio-8080-exec-4] c.s.r.service.HelloWorldGateway          : Inside fallbackForGetSeller, cause - io.github.resilience4j.circuitbreaker.CallNotPermittedException: CircuitBreaker 'hello-world' is OPEN and does not permit further calls
2020-07-28 00:07:29.298 ERROR 77427 --- [nio-8080-exec-6] c.s.r.service.HelloWorldGateway          : Inside fallbackForGetSeller, cause - io.github.resilience4j.circuitbreaker.CallNotPermittedException: CircuitBreaker 'hello-world' is OPEN and does not permit further calls
2020-07-28 00:07:29.539 ERROR 77427 --- [nio-8080-exec-7] c.s.r.service.HelloWorldGateway          : Inside fallbackForGetSeller, cause - io.github.resilience4j.circuitbreaker.CallNotPermittedException: CircuitBreaker 'hello-world' is OPEN and does not permit further calls
2020-07-28 00:07:29.727 ERROR 77427 --- [nio-8080-exec-8] c.s.r.service.HelloWorldGateway          : Inside fallbackForGetSeller, cause - io.github.resilience4j.circuitbreaker.CallNotPermittedException: CircuitBreaker 'hello-world' is OPEN and does not permit further calls
2020-07-28 00:07:29.943 ERROR 77427 --- [nio-8080-exec-9] c.s.r.service.HelloWorldGateway          : Inside fallbackForGetSeller, cause - io.github.resilience4j.circuitbreaker.CallNotPermittedException: CircuitBreaker 'hello-world' is OPEN and does not permit further calls

How to use Resilience4j in Spring Boot Application

Define @CircuitBreaker for the service call function:

@Slf4j
@Service
@RequiredArgsConstructor
public class HelloWorldGateway {

    private final RestTemplate restTemplate;

    @CircuitBreaker(name = "hello-world", fallbackMethod = "fallbackForHelloWorld")
    public String getHelloWorld() {
        log.info("calling getHelloWorld()");
        return restTemplate.getForObject("/world", String.class);
    }

    public String fallbackForHelloWorld(Throwable t) {
        log.error("Inside fallbackForGetSeller, cause - {}", t.toString());
        return "Sorry ... Service not available!!!";
    }
}

Define the resilience4j properties for "hello-world" in application.yml

resilience4j.circuitbreaker:
  instances:
    hello-world:
      registerHealthIndicator: true
      ringBufferSizeInClosedState: 7 # after 7 hits circuit will be opened
      ringBufferSizeInHalfOpenState: 5
      waitDurationInOpenState: 30s # 30 seconds is the lockin period once the circuit is open
      failureRateThreshold: 60
      

Call the defined @CircuitBreaker function in HelloWorld Service

Call the HelloWorld Service (getHelloWorld) from the HelloWorldGateway

@Service
@RequiredArgsConstructor
public class HelloWorldService {

    private final HelloWorldGateway helloWorldGateway;

    public String getHelloWorld() {
        return helloWorldGateway.getHelloWorld();
    }
}

License

See LICENSE file.