hystrix 学习

1、采用springboot + spring cloud hystrix 环境

2、pom.xml

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
    xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>
    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.1.3.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.example</groupId>
    <artifactId>hystrix</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>Hystrix</name>
    <description>Demo project for Spring Boot</description>

    <properties>
        <java.version>1.8</java.version>    
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        
        <!-- https://mvnrepository.com/artifact/org.springframework.cloud/spring-cloud-starter-netflix-hystrix -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-hystrix</artifactId>
            <version>2.1.1.RELEASE</version>
        </dependency>
        <!-- https://mvnrepository.com/artifact/org.springframework.cloud/spring-cloud-starter-netflix-hystrix-dashboard -->
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-hystrix-dashboard</artifactId>
            <version>2.1.1.RELEASE</version>
        </dependency>
        
         <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-actuator</artifactId>
        </dependency>
        
        
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>

</project>

3、启动类代码

package com.example.demo;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.web.servlet.ServletRegistrationBean;
import org.springframework.cloud.netflix.hystrix.EnableHystrix;
import org.springframework.cloud.netflix.hystrix.dashboard.EnableHystrixDashboard;
import org.springframework.context.annotation.Bean;

import com.netflix.hystrix.contrib.metrics.eventstream.HystrixMetricsStreamServlet;

@SpringBootApplication
@EnableHystrix
@EnableHystrixDashboard
public class HystrixApplication {

    public static void main(String[] args) {
        SpringApplication.run(HystrixApplication.class, args);
    }

     @Bean   //该方法的作用，是为了访问hystrix dashboard页面，/actuator/hystrix.stream就是hystrix 访问的地址
        public ServletRegistrationBean getServlet(){
            HystrixMetricsStreamServlet streamServlet = new HystrixMetricsStreamServlet();
            ServletRegistrationBean registrationBean = new ServletRegistrationBean(streamServlet);
            registrationBean.setLoadOnStartup(1);
            registrationBean.addUrlMappings("/actuator/hystrix.stream");
            registrationBean.setName("HystrixMetricsStreamServlet");
            return registrationBean;
        }
}

4. 服务器类代码

package com.example.demo;

import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

import com.netflix.hystrix.contrib.javanica.annotation.HystrixCommand;

@RestController
public class DeptRest {
    private static int a = 0;

    @RequestMapping(value="/dept/get/{id}", method = RequestMethod.GET)
    @HystrixCommand(fallbackMethod="getFallBack")
    public String get(@PathVariable("id") long id){
        a++;
        if(id == 0 && a>5){
            if(a>30){
                a =0;
            }
            throw new RuntimeException("对0不处理");
        }
        return "ok";
    }
    
    public String getFallBack(@PathVariable("id") long id){
        
        return "error";
    }
}

5.hystrix dashboard

• 下图中的url http://127.0.0.1:8080/actuator/hystrix.stream，在3、启动类代码中getServlet有注释说明
• 熔断初始界面，状态是关闭，如下图
• 
• 熔断打开监控界面，当在10秒出现20次错误，熔断打开，如下图

• 熔断关闭监控页面，小于阈值时，熔断变成关闭状态，如下图

 

6.如何访问达到阈值？

    测试工具jmeter