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本篇概览一起深刻理解Spring Cloud Gateway的断路器(CircuitBreaker)性能：先聊聊实践再联合官网和大神的信息确定技术栈再入手开发，先实现再验证再趁热打铁，看看它的源码最初，回顾一下有哪些有余（下一篇文章解决这些有余）对于断路器(CircuitBreaker)下图来自resilience4j官网文档，介绍了什么是断路器：
CLOSED状态时，申请失常放行申请失败率达到设定阈值时，变为OPEN状态，此时申请全副不放行OPEN状态继续设定工夫后，进入半开状态（HALE_OPEN），放过局部申请半开状态下，失败率低于设定阈值，就进入CLOSE状态，即全副放行半开状态下，失败率高于设定阈值，就进入OPEN状态，即全副不放行确认概念有个概念先确认一下，即<font color="blue">Spring Cloud断路器</font>与<font color="blue">Spring Cloud Gateway断路器性能</font>不是同一个概念，Spring Cloud Gateway断路器性能还波及过滤器，即在过滤器的规定下应用断路器：
本篇的重点是Spring Cloud Gateway如何配置和应用断路器（CircuitBreaker），因而不会探讨Resilience4J的细节，如果您想深刻理解Resilience4J，举荐材料是Spring Cloud Circuit Breaker对于Spring Cloud断路器先看Spring Cloud断路器，如下图，Hystrix、Sentinel这些都是相熟的概念：
对于Spring Cloud Gateway的断路器性能来看Spring Cloud Gateway的官网文档，如下图，有几个关键点稍后介绍：
上图走漏了几个要害信息：Spring Cloud Gateway内置了断路器filter，具体做法是应用Spring Cloud断路器的API，将gateway的路由逻辑封装到断路器中有多个断路器的库都能够用在Spring Cloud Gateway（遗憾的是没有列举是哪些）Resilience4J对Spring Cloud 来说是开箱即用的简略来说Spring Cloud Gateway的断路器性能是通过内置filter实现的，这个filter应用了Spring Cloud断路器；官网说多个断路器的库都能够用在Spring Cloud Gateway，然而并没有说具体是哪些，这就郁闷了，此时咱们去理解一位牛人的观点：Piotr Mińkowski，就是上面这本书的作者：
Piotr Mińkowski的博客对Spring Cloud Gateway的断路器性能做了具体介绍，如下图，有几个重要信息稍后会提到：
上图能够get到三个要害信息：从2.2.1版本起，Spring Cloud Gateway集成了Resilience4J的断路器实现Netflix的Hystrix进入了维护阶段（能了解为行将退休吗？）Netflix的Hystrix仍然可用，然而已废除(deprecated)，而且Spring Cloud未来的版本可能会不反对再关联到官网文档也以resilience4为例（如下图），胆大的我仿佛没有别的抉择了，就Resilience4J吧：
实践剖析就到此吧，接下来开始实战，具体的步骤如下：筹备工作：服务提供者新增一个web接口<font color="blue">/account/{id}</font>，依据入参的不同，该接口能够立刻返回或者延时500毫秒返回新增名为<font color="blue">circuitbreaker-gateway</font>的子工程，这是个带有断路器性能的Spring Cloud Gateway利用在<font color="blue">circuitbreaker-gateway</font>外面编写单元测试代码，用来验证断路器是否失常运行单元测试代码，察看断路器是否失效给断路器增加fallback并验证是否失效做一次简略的源码剖析，一为想深刻理解断路器的同学捋分明源码门路，二为测验本人以前理解的springboot常识在浏览源码时有么有帮忙源码下载本篇实战中的残缺源码可在GitHub下载到，地址和链接信息如下表所示(https://github.com/zq2599/blo...)：名称链接备注我的项目主页https://github.com/zq2599/blo...该我的项目在GitHub上的主页git仓库地址(https)https://github.com/zq2599/blo...该我的项目源码的仓库地址，https协定git仓库地址(ssh)git@github.com:zq2599/blog_demos.git该我的项目源码的仓库地址，ssh协定这个git我的项目中有多个文件夹，本篇的源码在<font color="blue">spring-cloud-tutorials</font>文件夹下，如下图红框所示：
<font color="blue">spring-cloud-tutorials</font>文件夹下有多个子工程，本篇的代码是<font color="red">circuitbreaker-gateway</font>，如下图红框所示：
筹备工作咱们要筹备一个可控的web接口，通过参数管制它胜利或者失败，这样能力触发断路器本篇的实战中，服务提供者仍旧是<font color="blue">provider-hello</font>，为了满足本次实战的需要，咱们在Hello.java文件中减少一个web接口，对应的源码如下： @RequestMapping(value = "/account/{id}", method = RequestMethod.GET) public String account(@PathVariable("id") int id) throws InterruptedException { if(1==id) { Thread.sleep(500); } return Constants.ACCOUNT_PREFIX + dateStr(); }上述代码很简略：就是接管id参数，如果等于1就延时五百毫秒，不等于1就立刻返回如果把断路器设置为超过两百毫秒就算失败，那么通过管制id参数的值，咱们就能模仿申请胜利或者失败了，<font color="blue">这是验证断路器性能的要害</font>筹备实现，开始写代码实战在父工程<font color="blue">spring-cloud-tutorials</font>上面新增子工程<font color="blue">circuitbreaker-gateway</font>减少以下依赖<dependency> <groupId>org.springframework.cloud</groupId> <artifactId>spring-cloud-starter-circuitbreaker-reactor-resilience4j</artifactId></dependency>配置文件application.yml如下：server: #服务端口 port: 8081spring: application: name: circuitbreaker-gateway cloud: gateway: routes: - id: path_route uri: http://127.0.0.1:8082 predicates: - Path=/hello/** filters: - name: CircuitBreaker args: name: myCircuitBreaker启动类：package com.bolingcavalry.circuitbreakergateway;import org.springframework.boot.SpringApplication;import org.springframework.boot.autoconfigure.SpringBootApplication;@SpringBootApplicationpublic class CircuitbreakerApplication { public static void main(String[] args) { SpringApplication.run(CircuitbreakerApplication.class,args); }}配置类如下，这是断路器相干的参数配置：package com.bolingcavalry.circuitbreakergateway.config;import io.github.resilience4j.circuitbreaker.CircuitBreakerConfig;import io.github.resilience4j.timelimiter.TimeLimiterConfig;import org.springframework.cloud.circuitbreaker.resilience4j.ReactiveResilience4JCircuitBreakerFactory;import org.springframework.cloud.circuitbreaker.resilience4j.Resilience4JConfigBuilder;import org.springframework.context.annotation.Bean;import org.springframework.context.annotation.Configuration;import java.time.Duration;@Configurationpublic class CustomizeCircuitBreakerConfig { @Bean public ReactiveResilience4JCircuitBreakerFactory defaultCustomizer() { CircuitBreakerConfig circuitBreakerConfig = CircuitBreakerConfig.custom() // .slidingWindowType(CircuitBreakerConfig.SlidingWindowType.TIME_BASED) // 滑动窗口的类型为工夫窗口 .slidingWindowSize(10) // 工夫窗口的大小为60秒 .minimumNumberOfCalls(5) // 在单位工夫窗口内起码须要5次调用能力开始进行统计计算 .failureRateThreshold(50) // 在单位工夫窗口内调用失败率达到50%后会启动断路器 .enableAutomaticTransitionFromOpenToHalfOpen() // 容许断路器主动由关上状态转换为半开状态 .permittedNumberOfCallsInHalfOpenState(5) // 在半开状态下容许进行失常调用的次数 .waitDurationInOpenState(Duration.ofSeconds(5)) // 断路器关上状态转换为半开状态须要期待60秒 .recordExceptions(Throwable.class) // 所有异样都当作失败来解决 .build(); ReactiveResilience4JCircuitBreakerFactory factory = new ReactiveResilience4JCircuitBreakerFactory(); factory.configureDefault(id -> new Resilience4JConfigBuilder(id) .timeLimiterConfig(TimeLimiterConfig.custom().timeoutDuration(Duration.ofMillis(200)).build()) .circuitBreakerConfig(circuitBreakerConfig).build()); return factory; }}上述代码有一次须要留神：<font color="blue">timeLimiterConfig</font>办法设置了超时工夫，服务提供者如果超过200毫秒没有响应，Spring Cloud Gateway就会向调用者返回失败开发实现了，接下来要思考的是如何验证单元测试类为了验证Spring Cloud Gateway的断路器性能，咱们能够用Junit单元测试来准确管制申请参数和申请次数，测试类如下，可见测试类会间断发一百次申请，在前五十次中，申请参数始终在0和1之间切换，参数等于1的时候，接口会有500毫秒延时，超过了Spring Cloud Gateway的200毫秒超时限度，这时候就会返回失败，等失败多了，就会触发断路器的断开：package com.bolingcavalry.circuitbreakergateway;import io.github.resilience4j.circuitbreaker.CircuitBreaker;import org.junit.jupiter.api.RepeatedTest;import org.junit.jupiter.api.Test;import org.junit.jupiter.api.extension.ExtendWith;import org.springframework.beans.factory.annotation.Autowired;import org.springframework.boot.test.autoconfigure.web.reactive.AutoConfigureWebTestClient;import org.springframework.boot.test.context.SpringBootTest;import org.springframework.http.MediaType;import org.springframework.test.context.junit.jupiter.SpringExtension;import org.springframework.test.web.reactive.server.WebTestClient;@SpringBootTest@ExtendWith(SpringExtension.class)@AutoConfigureWebTestClientpublic class CircuitbreakerTest { // 测试的总次数 private static int i=0; @Autowired private WebTestClient webClient; @Test @RepeatedTest(100) void testHelloPredicates() throws InterruptedException { // 低于50次时，gen在0和1之间切换，也就是一次失常一次超时， // 超过50次时，gen固定为0，此时每个申请都不会超时 int gen = (i<50) ? (i % 2) : 0; // 次数加一 i++; final String tag = "[" + i + "]"; // 发动web申请 webClient.get() .uri("/hello/account/" + gen) .accept(MediaType.APPLICATION_JSON) .exchange() .expectBody(String.class).consumeWith(result -> System.out.println(tag + result.getRawStatusCode() + " - " + result.getResponseBody())); Thread.sleep(1000); }}验证启动nacos（服务提供者依赖的）启动子工程<font color="blue">provider-hello</font>运行咱们方才开发的单元测试类，控制台输出的内容截取局部如下，稍后会有剖析：[2]504 - {"timestamp":"2021-08-28T02:55:42.920+00:00","path":"/hello/account/1","status":504,"error":"Gateway Timeout","message":"","requestId":"594efed1"}[3]200 - Account2021-08-28 10:55:43[4]504 - {"timestamp":"2021-08-28T02:55:45.177+00:00","path":"/hello/account/1","status":504,"error":"Gateway Timeout","message":"","requestId":"427720b"}[5]200 - Account2021-08-28 10:55:46[6]503 - {"timestamp":"2021-08-28T02:55:47.227+00:00","path":"/hello/account/1","status":503,"error":"Service Unavailable","message":"","requestId":"6595d7f4"}[7]503 - {"timestamp":"2021-08-28T02:55:48.250+00:00","path":"/hello/account/0","status":503,"error":"Service Unavailable","message":"","requestId":"169ae1c"}[8]503 - {"timestamp":"2021-08-28T02:55:49.259+00:00","path":"/hello/account/1","status":503,"error":"Service Unavailable","message":"","requestId":"53b695a1"}[9]503 - {"timestamp":"2021-08-28T02:55:50.269+00:00","path":"/hello/account/0","status":503,"error":"Service Unavailable","message":"","requestId":"4a072f52"}[10]504 - {"timestamp":"2021-08-28T02:55:51.499+00:00","path":"/hello/account/1","status":504,"error":"Gateway Timeout","message":"","requestId":"4bdd96c4"}[11]200 - Account2021-08-28 10:55:52[12]504 - {"timestamp":"2021-08-28T02:55:53.745+00:00","path":"/hello/account/1","status":504,"error":"Gateway Timeout","message":"","requestId":"4e0e7eab"}[13]200 - Account2021-08-28 10:55:54[14]504 - {"timestamp":"2021-08-28T02:55:56.013+00:00","path":"/hello/account/1","status":504,"error":"Gateway Timeout","message":"","requestId":"27685405"}[15]503 - {"timestamp":"2021-08-28T02:55:57.035+00:00","path":"/hello/account/0","status":503,"error":"Service Unavailable","message":"","requestId":"3e40c5db"}[16]503 - {"timestamp":"2021-08-28T02:55:58.053+00:00","path":"/hello/account/1","status":503,"error":"Service Unavailable","message":"","requestId":"2bf2698b"}[17]503 - {"timestamp":"2021-08-28T02:55:59.075+00:00","path":"/hello/account/0","status":503,"error":"Service Unavailable","message":"","requestId":"38cb1840"}[18]503 - {"timestamp":"2021-08-28T02:56:00.091+00:00","path":"/hello/account/1","status":503,"error":"Service Unavailable","message":"","requestId":"21586fa"}[19]200 - Account2021-08-28 10:56:01[20]504 - {"timestamp":"2021-08-28T02:56:02.325+00:00","path":"/hello/account/1","status":504,"error":"Gateway Timeout","message":"","requestId":"4014d6d4"}[21]200 - Account2021-08-28 10:56:03[22]504 - {"timestamp":"2021-08-28T02:56:04.557+00:00","path":"/hello/account/1","status":504,"error":"Gateway Timeout","message":"","requestId":"173a3b9d"}[23]200 - Account2021-08-28 10:56:05[24]504 - {"timestamp":"2021-08-28T02:56:06.811+00:00","path":"/hello/account/1","status":504,"error":"Gateway Timeout","message":"","requestId":"aa8761f"}[25]200 - Account2021-08-28 10:56:07[26]504 - {"timestamp":"2021-08-28T02:56:09.057+00:00","path":"/hello/account/1","status":504,"error":"Gateway Timeout","message":"","requestId":"769bfefc"}[27]200 - Account2021-08-28 10:56:10[28]504 - {"timestamp":"2021-08-28T02:56:11.314+00:00","path":"/hello/account/1","status":504,"error":"Gateway Timeout","message":"","requestId":"2fbcb6c0"}[29]503 - {"timestamp":"2021-08-28T02:56:12.332+00:00","path":"/hello/account/0","status":503,"error":"Service Unavailable","message":"","requestId":"58e4e70f"}[30]503 - {"timestamp":"2021-08-28T02:56:13.342+00:00","path":"/hello/account/1","status":503,"error":"Service Unavailable","message":"","requestId":"367651c5"}剖析上述输入的返回码：504是超时返回的谬误，200是服务提供者的失常返回504和200两种返回码都示意申请达到了服务提供者，所以此时断路器是敞开状态屡次504谬误后，达到了配置的门限，触发断路器开启间断呈现的503就是断路器开启后的返回码，此时申请是无奈达到服务提供者的间断的503之后，504和200再次交替呈现，证实此时进入半开状态，而后504再次达到门限触发断路器从半开转为开启，五十次之后，因为不在发送超时申请，断路器进入敞开状态fallback通过上述测试可见，Spring Cloud Gateway通过返回码来告知调用者错误信息，这种形式不够敌对，咱们能够自定义fallback，在返回谬误时由它来构建返回信息再开发一个web接口，没错，就是在<font color="blue">circuitbreaker-gateway</font>工程中增加一个web接口：package com.bolingcavalry.circuitbreakergateway.controller;import org.springframework.web.bind.annotation.GetMapping;import org.springframework.web.bind.annotation.RestController;import java.text.SimpleDateFormat;import java.util.Date;@RestControllerpublic class Fallback { private String dateStr(){ return new SimpleDateFormat("yyyy-MM-dd hh:mm:ss").format(new Date()); } /** * 返回字符串类型 * @return */ @GetMapping("/myfallback") public String helloStr() { return "myfallback, " + dateStr(); }}application.yml配置如下，可见是给filter减少了<font color="blue">fallbackUri</font>属性：server: #服务端口 port: 8081spring: application: name: circuitbreaker-gateway cloud: gateway: routes: - id: path_route uri: http://127.0.0.1:8082 predicates: - Path=/hello/** filters: - name: CircuitBreaker args: name: myCircuitBreaker fallbackUri: forward:/myfallback再运行单元测试，可见返回码全副是200，原来的谬误当初全副变成了方才新增的接口的返回内容：[2]200 - myfallback, 2021-08-28 11:15:02[3]200 - Account2021-08-28 11:15:03[4]200 - myfallback, 2021-08-28 11:15:04[5]200 - Account2021-08-28 11:15:05[6]200 - myfallback, 2021-08-28 11:15:06[7]200 - myfallback, 2021-08-28 11:15:08[8]200 - myfallback, 2021-08-28 11:15:09[9]200 - myfallback, 2021-08-28 11:15:10[10]200 - myfallback, 2021-08-28 11:15:11[11]200 - Account2021-08-28 11:15:12[12]200 - myfallback, 2021-08-28 11:15:13[13]200 - Account2021-08-28 11:15:14[14]200 - myfallback, 2021-08-28 11:15:15至此，咱们已实现了Spring Cloud Gateway的断路器性能的开发和测试，如果聪慧好学的您并不满足这寥寥几行配置和代码，想要深刻理解断路器的外部，那么请您接往下看，咱们聊聊它的源码；源码剖析RouteDefinitionRouteLocator的构造方法（bean注入）中有如下代码，将name和实例绑定：gatewayFilterFactories.forEach(factory -> this.gatewayFilterFactories.put(factory.name(), factory));而后会在loadGatewayFilters办法中应用这个map，找到下面put的bean；最终的成果：路由配置中指定了name等于<font color="blue">CircuitBreaker</font>，即可对应SpringCloudCircuitBreakerFilterFactory类型的bean，因为它的name办法返回了"CircuitBreaker"，如下图：
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