java：测试hystrix的一些关键参数

# 参考资料

https://www.cnblogs.com/zhenbianshu/p/9630167.html

# 示例程序如下：

【pom.xml】

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
    <version>2.3.12.RELEASE</version>
</dependency>
<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-actuator</artifactId>
    <version>2.3.12.RELEASE</version>
</dependency>
<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
    <version>2.2.10.RELEASE</version>
</dependency>
<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-netflix-ribbon</artifactId>
    <version>2.2.9.RELEASE</version>
</dependency>
<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-openfeign</artifactId>
    <version>2.2.9.RELEASE</version>
</dependency>
<dependency>
    <groupId>org.springframework.cloud</groupId>
    <artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
    <version>2.2.10.RELEASE</version>
</dependency>
<dependency>
    <groupId>ch.qos.logback</groupId>
    <artifactId>logback-classic</artifactId>
    <version>1.2.12</version>
</dependency>

【application.properties】

server.port=8080
spring.application.name=myFeignClient

management.server.port=7001
management.endpoints.web.exposure.include=*

eureka.client.serviceUrl.defaultZone=http://localhost:8761/eureka/,http://localhost:8762/eureka/,http://localhost:8763/eureka/
eureka.client.register-with-eureka=true
eureka.client.serviceUrl.instance.prefer-ip-address=true

#feign.client.config.myFeignClient.connectTimeout=10000
#feign.client.config.myFeignClient.readTimeout=20000          # 甚至可以针对一个FeignClient进行配置
feign.client.config.default.connectTimeout=5000
feign.client.config.default.readTimeout=10000
feign.hystrix.enabled=true

hystrix.command.default.execution.isolation.thread.timeoutInMilliseconds=2000
hystrix.command.default.metrics.rollingStats.timeInMilliseconds=3000
hystrix.command.default.circuitBreaker.requestVolumeThreshold=1
hystrix.command.default.circuitBreaker.errorThresholdPercentage=1
hystrix.command.default.circuitBreaker.sleepWindowInMilliseconds=5000

logging.level.root=info
logging.level.com.chz.myFeignClient=DEBUG

参数解释：

• 【feign.client.config.default.readTimeout=10000】：因为hystrix的熔断时间设为2000，所以feign的timeout时间设大一点，以免受这个readTimeout的影响
• 【hystrix.command.default.execution.isolation.thread.timeoutInMilliseconds=2000】：feign调用外部接口超过2秒就会发生熔断
• 【hystrix.command.default.metrics.rollingStats.timeInMilliseconds=3000】：hystrix的滑动窗口设为3秒，即发生首次熔断之后3秒内再次调用时自动熔断
• 【hystrix.command.default.circuitBreaker.requestVolumeThreshold=1】：滑动窗口内只要有一个请求就会触发【circuitBreaker.errorThresholdPercentage】参数的运算。生产环境千万不要这样设，只是为了测试。
• 【hystrix.command.default.circuitBreaker.errorThresholdPercentage=1】：滑动窗口内的请求有1%是失败的就会触发自动熔断。生产环境千万不要这样设，只是为了测试。
• 【hystrix.command.default.circuitBreaker.sleepWindowInMilliseconds=5000】：自动熔断时间为5秒钟，即熔断发生5秒后自动熔断才会有机会恢复

【FeignConfiguration.java】

package com.chz.myFeignClient.config;

@Configuration
public class FeignConfiguration 
{
    @Bean
    Logger.Level feignLoggerLevel() {
        return Logger.Level.FULL;
    }
}

【Test2Controller.java】

package com.chz.myFeignClient.controller;

@Slf4j
@RestController
@RequestMapping("/test2")
public class Test2Controller {

    @Autowired
    private Test1FeignClient test1FeignClient;

    @GetMapping("/test")
    public String test() {
        log.info("chz >>> Test2Controller.test()");
        String result = test1FeignClient.hello();
        log.info("chz >>> Test2Controller.test(): {}", result);
        return result;
    }
}

【Test1FeignClient.java】

package com.chz.myFeignClient.feign;

@FeignClient(
        contextId = "com.chz.myFeignClient.feign.Test1FeignClient",
        name = "myEurekaClient1",
        path = "/test",
        fallbackFactory = Test1FeignClientFallback.class
)
public interface Test1FeignClient
{
    @GetMapping(value = "/hello")
    String hello();
}

@Slf4j
@Component
class Test1FeignClientFallback implements FallbackFactory<Test1FeignClient>
{
    @Override
    public Test1FeignClient create(Throwable cause) {
        return new Test1FeignClient() {
            @Override
            public String hello() {
                log.error("chz >>> Test1FeignClientFallback.hello() -> fallback", cause);
                return "fallback hello";
            }
        };
    }
}

说明：远程调用的接口【http://myEurekaClient1/test/hello】有50%左右的机会会休眠3000秒，关键代码如下：

@GetMapping("/hello")
public String hello() {
    log.info("chz >>> TestController.hello()");
    try {
        if( Math.abs(ThreadLocalRandom.current().nextInt() % 2)==0 ) {
            log.info("chz >>> TestController.hello(), sleep");
            Thread.sleep(3000L);
        }
    } catch (InterruptedException e) {
        log.info("interrupt", e);
    }
    log.info("chz >>> TestController.hello(), result");
    return "Hello: " + serverPort;
}

【FeignRequestInterceptor.java】

package com.chz.myFeignClient.interceptor;

@Slf4j
@Configuration
public class FeignRequestInterceptor implements RequestInterceptor
{
    @Override
    public void apply(RequestTemplate template)
    {
        // 这里给每一个FeignClient的调用增加一个header
        log.info("FeignRequestInterceptor::apply: tid:{}", Thread.currentThread().getId());
        template.header("chz-new-header", "just-for-test");
    }
}

【MyFeignClientTest.java】

package com.chz.myFeignClient;

@EnableHystrix
@EnableFeignClients
@SpringBootApplication
public class MyFeignClientTest 
{
    public static void main(String[] args) {
        SpringApplication.run(MyFeignClientTest.class, args);
    }
}

运行【MyFeignClientTest】，然后不断访问【http://localhost:8080/test2/test】，查看日志

从截图可以看出超过了5秒之后自动熔断才恢复，符合预期