Spring Boot Circuit Breaker (resilience4j demo)

This repository demonstrates how to build fault-tolerant application and apply resiliency patterns using Resilience4j.

Features

• Example of most common resilience patterns (circuit breaker, retry, bulkhead and time limiter).
• Metrics.
• Micrometer/Prometheus integration.
• Resilience4j Grafana dashboard.
• Docker compose running demo.

Application Diagram

Getting Started

Prerequisites

• Java 11
• Docker
• Docker-Compose
• ab - Apache HTTP server benchmarking tool

Installation

Build docker image.

./gradlew bootBuildImage

Usage

• Start docker compose (keycloak and postgres)

  cd docker
  
  docker-compose up -d

• List containers and check if all are Up.

  docker-compose ps   
  
  #        Name                      Command                  State               Ports         
  # --------------------------------------------------------------------------------------------
  # circuitbreaker-demo   /cnb/process/web                 Up             0.0.0.0:8080->8080/tcp
  # grafana               /run.sh                          Up (healthy)   0.0.0.0:3000->3000/tcp
  # prometheus            /bin/prometheus --config.f ...   Up (healthy)   0.0.0.0:9090->9090/tcp

• Generate website traffic using Apache Benchmark tool.

  # Circuit Breaker - `sayHello`
  ab -t 60 -c 20 http://localhost:8080/api/hello?name=ab_test
  
  # Circuit Breaker - `success` 
  ab -t 30 -c 10 http://localhost:8080/api/hello/success

• Open your web browser and go to Grafana login page. Inside the login page, enter admin for a username and password.

• Open demo/Resilience4j dashboard. You should be able to see circuit breaker metrics as shown below:

• Stop demo and cleanup volumes.

  docker-compose down -v

Important Endpoints

Name	Endpoint
Demo application	http://localhost:8080
Prometheus	http://localhost:9090/
Grafana	http://localhost:3000/
Actuator endpoint	http://localhost:8080/actuator
Bulkheads - Actuator	http://localhost:8080/actuator/bulkheads
Bulkheads events - Actuator	http://localhost:8080/actuator/bulkheadevents
Micrometer Prometheus - Actuator	http://localhost:8080/actuator/prometheus
Circuit breakers - Actuator	http://localhost:8080/actuator/circuitbreakers
Circuit breakers events - Actuator	http://localhost:8080/actuator/circuitbreakerevents
Rate limiters - Actuator	http://localhost:8080/actuator/ratelimiters
Rate limiters events - Actuator	http://localhost:8080/actuator/ratelimiterevents
Retries - Actuator	http://localhost:8080/actuator/retries
Retries events - Actuator	http://localhost:8080/actuator/retryevents
Time limiters - Actuator	http://localhost:8080/actuator/timelimiters
Time limiters events - Actuator	http://localhost:8080/actuator/timelimiterevents
Actuator health	http://localhost:8080/actuator/health

Additional tips

Replacing java annotations with custom resiliency4j operator.

import io.github.resilience4j.circuitbreaker.CircuitBreaker;
import io.github.resilience4j.circuitbreaker.CircuitBreakerRegistry;
import io.github.resilience4j.reactor.circuitbreaker.operator.CircuitBreakerOperator;
import reactor.core.publisher.Mono;

// example how to decorate a Mono using custom Reactor operator.
public class IfYouHateAnnotationsServiceExample {

	private final CircuitBreaker circuitBreaker;

	public IfYouHateAnnotationsServiceExample(CircuitBreakerRegistry circuitBreakerRegistry) {
		circuitBreaker = circuitBreakerRegistry.circuitBreaker("hello_world");
	}

	Mono<String> helloWorld() {
		return Mono.fromCallable(() -> "Hello World!")
				   .transformDeferred(CircuitBreakerOperator.of(circuitBreaker));
	}
}

References

For further reference, please consider the following sections:

• Application resiliency patterns
• Resilience4J
• Getting started with resilience4j-spring-boot2
• Examples of resilience4j-reactor
• Resilience4j Grafana Dashboard
• Prometheus

License

Distributed under the MIT License. See LICENSE for more information.