微服务中关于feign整合hystrix的案例使用以及注意事项

2018年12月19日 22:23:06 uniquewdl 阅读数：134

What Is Hystrix?

在一个分布式系统里，许多依赖不可避免的会调用失败，比如超时、异常等，如何能够保证在一个依赖出问题的情况下，不会导致整体服务失败，这个就是Hystrix需要做的事情。Hystrix提供了熔断、隔离、Fallback、cache、监控等功能，能够在一个、或多个依赖同时出现问题时保证系统依然可用。知道它的，作用优点和好处了。那么下边就跟着我一起来操作一下feign整合Hystrix。

1.创建feign项目

1.pom文件

<?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>
<artifactId>feign-customizing</artifactId>
<packaging>jar</packaging>
<parent>
<groupId>com.itmuch.cloud</groupId>
<artifactId>microservice-spring-cloud</artifactId>
<version>0.0.1-SNAPSHOT</version>
</parent>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<java.version>1.8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-eureka</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-feign</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-hystrix-dashboard</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-hystrix</artifactId>
</dependency>
</dependencies>
</project>

---------------pom文件的注意点就是一定要注意springboot的版本，版本不能太高。否则会报错找不到方法的异常。具体分析在后续博客中会详细分析。

2.配置文件：

application.yml文件

spring:
application:
name: microservice-consumer-movie
server:
port: 2000
eureka:
client:
healthcheck:
enabled: true
serviceUrl:
defaultZone: http://47.xxx.6.xxx:1000/eureka
instance:
prefer-ip-address: true
logging:
level:
com.itmuch.cloud.feign.UserFeignClient: DEBUG

注意点：

#可以通过下边的配置设置超时时间，默认为一秒即为1000：

也可以通过下边的设置来更好的观察项目的效果
# hystrix.command.default.execution.isolation.thread.timeoutInMilliseconds: 5000
# 或者：
# hystrix.command.default.execution.timeout.enabled: false
# 或者：
feign.hystrix.enabled: true ## 索性禁用feign的hystrix

# 超时的issue：https://github.com/spring-cloud/spring-cloud-netflix/issues/768
# 超时的解决方案： http://stackoverflow.com/questions/27375557/hystrix-command-fails-with-timed-out-and-no-fallback-available
# hystrix配置： https://github.com/Netflix/Hystrix/wiki/Configuration#execution.isolation.thread.timeoutInMilliseconds

3，启动类

Applicatoin

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.cloud.netflix.feign.EnableFeignClients;
import org.springframework.cloud.netflix.hystrix.dashboard.EnableHystrixDashboard;
@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients
@EnableHystrixDashboard
public class MyFeignApplication {
public static void main(String[] args) {
SpringApplication.run(MyFeignApplication.class, args);
}
}

注意点：四个注解缺一不可：

@SpringBootApplication
@EnableDiscoveryClient
@EnableFeignClients
@EnableHystrixDashboard

4.建立controller

package com.itmuch.cloud.controller;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import com.itmuch.cloud.entity.User;
import com.itmuch.cloud.feign.FeignClient2;
import com.itmuch.cloud.feign.UserFeignClient;
@RestController
public class TestController {
@Autowired
private UserFeignClient userFeignClient;
@RequestMapping("/index")
public String index() {
String str = userFeignClient.getContext();
return str;
}
}

这里的controller是一个外部入口，通过请求index方法进而调用下边的feign方法，

5.feign的接口配置（重点）

import org.springframework.cloud.netflix.feign.FeignClient;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
@FeignClient(name = "feign-user", fallback = MyHystrix.class)
public interface UserFeignClient {
@RequestMapping(value="/getContext",method=RequestMethod.GET)
public String getContext();
}

注意点：@FeignClient(name = "feign-user", fallback = MyHystrix.class) 这里就是feign的核心配置，name属性是feign请求外部接口的服务名称（就是一同注册到注册中心的服务名称） fallback就是产生异常错误后的回退路径

要求fallback指向的类必须实现feign接口。然后再对应的接口的实现具体实现自定义的异常处理（抛错，提示异常，回退等操作）。注意点2feign中的方法注解不支持GetMapping 以及如果是@PathVariable一定要有值。

附加fallback的类

import org.springframework.stereotype.Component;
@Component
public class MyHystrix implements UserFeignClient {
@Override
public String getContext() {
System.err.println("=======报错");
return "报错了";
}
}

说明，如果是UserFeignClient的某个方法由于超时，异常等非正常操作都会进入对应Hystrix方法中，这样更好地捕获异常和进行处理。

6.新建一个项目作为feign的请求项目，要求该项目也能够注册到注册中心上（eureka等）

下边不做详细说明核心代码如下:

7.pom文件

<?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>
<artifactId>movie-feign</artifactId>
<packaging>jar</packaging>
<parent>
<groupId>com.itmuch.cloud</groupId>
<artifactId>microservice-spring-cloud</artifactId>
<version>0.0.1-SNAPSHOT</version>
</parent>
<properties>
<project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
<project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding>
<java.version>1.8</java.version>
</properties>
<dependencies>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-web</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-eureka</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-actuator</artifactId>
</dependency>
<dependency>
<groupId>org.springframework.cloud</groupId>
<artifactId>spring-cloud-starter-feign</artifactId>
</dependency>
</dependencies>
</project>

8.application.yml

spring:
application:
name: provider-user
server:
port: 2001
eureka:
client:
healthcheck:
enabled: true
serviceUrl:
defaultZone: http://47.xxx.6.xxx:1000/eureka
instance:
prefer-ip-address: true

9.请求端controller

package com.itmuch.cloud.controller;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import com.itmuch.cloud.entity.User;
import com.itmuch.cloud.feign.UserFeignClient;
@RestController
public class MovieController {
/*
* @GetMapping("/test") public User testPost(User user) { return
* this.userFeignClient.postUser(); }
*
* @GetMapping("/test-get") public User testGet(User user) { return
* this.userFeignClient.getUser(user); }
*/
@RequestMapping("/getContext")
public String getContext() {
return "我是服务端的getContext方法";
}
}

10.最后来波效果图：

10-1eureka注册中心

微服务中关于feign整合hystrix的案例使用以及注意事项

10-2 失败结果

微服务中关于feign整合hystrix的案例使用以及注意事项

10-3成功

微服务中关于feign整合hystrix的案例使用以及注意事项

微服务中关于feign整合hystrix的案例使用以及注意事项

微服务中关于feign整合hystrix的案例使用以及注意事项

What Is Hystrix?

1.创建feign项目

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