Spring Cloud Circuit Breaker

Introduction

Spring Cloud Circuit breaker provides an abstraction across different circuit breaker implementations. It provides a consistent API to use in your applications allowing you the developer to choose the circuit breaker implementation that best fits your needs for your app.

Supported Implementations

Core Concepts

To create a circuit breaker in your code you can use the CircuitBreakerFactory API. When you include a Spring Cloud Circuit Breaker starter on your classpath a bean implementing this API will automatically be created for you. A very simple example of using this API is given below

@Service
public static class DemoControllerService {
	private RestTemplate rest;
	private CircuitBreakerFactory cbFactory;

	public DemoControllerService(RestTemplate rest, CircuitBreakerFactory cbFactory) {
		this.rest = rest;
		this.cbFactory = cbFactory;
	}

	public String slow() {
		return cbFactory.create("slow").run(() -> rest.getForObject("/slow", String.class), throwable -> "fallback");
	}

}

The CircuitBreakerFactory.create API will create an instance of a class called CircuitBreaker. The run method takes a Supplier and a Function. The Supplier is the code that you are going to wrap in a circuit breaker. The Function is the fallback that will be executed if the circuit breaker is tripped. The function will be passed the Throwable that caused the fallback to be triggered. You can optionally exclude the fallback if you do not want to provide one.

Circuit Breakers In Reactive Code

If Project Reactor is on the class path then you can also use ReactiveCircuitBreakerFactory for your reactive code.

@Service
public static class DemoControllerService {
	private ReactiveCircuitBreakerFactory cbFactory;
	private WebClient webClient;


	public DemoControllerService(WebClient webClient, ReactiveCircuitBreakerFactory cbFactory) {
		this.webClient = webClient;
		this.cbFactory = cbFactory;
	}

	public Mono<String> slow() {
		return webClient.get().uri("/slow").retrieve().bodyToMono(String.class).transform(
		it -> cbFactory.create("slow").run(it, throwable -> return Mono.just("fallback")));
	}
}

The ReactiveCircuitBreakerFactory.create API will create an instance of a class called ReactiveCircuitBreaker. The run method takes with a Mono or Flux and wraps it in a circuit breaker. You can optionally profile a fallback Function which will be called if the circuit breaker is tripped and will be passed the Throwable that caused the failure.

Spring Boot Config

The following starters are available with the Spring Cloud BOM

Resilience4J - org.springframework.cloud:spring-cloud-starter-circuitbreaker-resilience4j
Reactive Resilience4J - org.springframework.cloud:spring-cloud-starter-circuitbreaker-reactor-resilience4j
Spring Retry - org.springframework.cloud:spring-cloud-starter-circuitbreaker-spring-retry

Quickstart Your Project

Bootstrap your application with Spring Initializr.

Documentation

Each Spring project has its own; it explains in great details how you can use project features and what you can achieve with them.

2.1.3 CURRENT GA	Reference Doc.
3.0.0-M3 PRE	Reference Doc.
2.1.4-SNAPSHOT SNAPSHOT	Reference Doc.
2.0.4-SNAPSHOT SNAPSHOT	Reference Doc.
2.0.3 GA	Reference Doc.
1.0.7.BUILD-SNAPSHOT SNAPSHOT	Reference Doc.
1.0.6.RELEASE GA	Reference Doc.

Branch	Initial Release	End of Support	End Commercial Support *
2.1.x	2021-11-30	2023-05-18	2024-09-18
2.0.x	2020-12-21	2022-05-19	2023-09-19
1.0.x	2019-11-26	2020-11-26	2022-03-26

OSS support

Free security updates and bugfixes with support from the Spring community. See VMware Tanzu OSS support policy.

Commercial support

Business support from Spring experts during the OSS timeline, plus extended support after OSS End-Of-Life.
Publicly available releases for critical bugfixes and security issues when requested by customers.

Future release

Generation not yet released, timeline is subject to changes.

About commercial support (*)

This page shows the current state of project releases and does not define the commercial support policy. Please refer to the official support policy for more information.

Learn more about commercial support.

A few examples to try out:

Spring Cloud Circuit Breaker Demo