关于feign client触发熔断的异常

Posted 2023-04-23

参考技术A 使用feign client进行restful服务间的调用，除了要注意超时时间、retry的设置外，还有一个关于自定义异常的部分，需要注意一下，不然容易出错。

Nginx 默认判断失败节点状态以connect refuse和time out状态为准，不以HTTP错误状态进行判断失败，因为HTTP只要能返回状态说明该节点还可以正常连接，所以nginx判断其还是存活状态；除非添加了proxy_next_upstream指令设置对404、502、503、504、500和time out等错误进行转到备机处理。

这个异常主要是用来适配IllegalArgumentException这类异常。HystrixBadRequestException与其他HystrixCommand抛出的异常不同，该异常不会纳入circuit breaker的统计里头，即不会触发熔断。

/Users/xixicat/.m2/repository/io/github/openfeign/feign-core/9.3.1/feign-core-9.3.1-sources.jar!/feign/SynchronousMethodHandler.java

其中对status code的处理见这段

要特别注意，对于restful抛出的4xx的错误，也许大部分是业务异常，并不是服务提供方的异常，因此在进行feign client调用的时候，需要进行errorDecoder去处理，适配为HystrixBadRequestException，好避开circuit breaker的统计，否则就容易误判，传几个错误的参数，立马就熔断整个服务了，后果不堪设想。

Feign + Hystrix 服务熔断和服务降级

本机IP为  192.168.1.102

 

1.    新建 Maven 项目   feign

 

2.   pom.xml

<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>
    <groupId>com.java</groupId>
    <artifactId>feign</artifactId>
    <version>1.0.0-SNAPSHOT</version>
    <name>${project.artifactId}</name>

    <!-- 配置版本常量 -->
    <properties>
        <jdk.version>1.8</jdk.version>
        <spring.cloud.version>2.0.0.RELEASE</spring.cloud.version>
    </properties>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.5.RELEASE</version>
    </parent>

    <dependencies>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-web</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
            <version>${spring.cloud.version}</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-openfeign</artifactId>
            <version>${spring.cloud.version}</version>
        </dependency>

        <dependency>
            <groupId>com.alibaba</groupId>
            <artifactId>fastjson</artifactId>
            <version>1.2.49</version>
        </dependency>
        <dependency>
            <groupId>org.projectlombok</groupId>
            <artifactId>lombok</artifactId>
            <scope>provided</scope>
        </dependency>


        <!-- 热部署 -->
        <dependency>
            <groupId>org.springframework</groupId>
            <artifactId>springloaded</artifactId>
            <version>1.2.8.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-devtools</artifactId>
        </dependency>

    </dependencies>

    <build>
        <finalName>${project.artifactId}</finalName>
        <plugins>
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-compiler-plugin</artifactId>
                <configuration>
                    <source>${jdk.version}</source>
                    <target>${jdk.version}</target>
                    <encoding>UTF-8</encoding>
                </configuration>
            </plugin>

            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
                <executions>
                    <execution>
                        <goals>
                            <goal>repackage</goal>
                        </goals>
                    </execution>
                </executions>
            </plugin>
        </plugins>
    </build>
</project>

 

 

3.   application.yml

server:
  port: 80
  

feign: 
  hystrix: 
    enabled: true



eureka:
  client:
    register-with-eureka: false
    service-url: 
      defaultZone: http://192.168.1.102:8080/eureka/  
      #defaultZone: http://s0.com:8080/eureka/,http://s1.com:8080/eureka/,http://s2.com:8080/eureka/

 

 

4.   HostService.java

package com.java.feign.service;

import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.PathVariable;

import com.alibaba.fastjson.JSONObject;

@FeignClient(value = "MICROSERVICE", fallbackFactory = HostServiceFallbackFactory.class)
public interface HostService {

    @GetMapping("/getHostMessage/{id}")
    public JSONObject getHostMessage(@PathVariable(value = "id") String id);

}

 

 

5.   HostServiceFallbackFactory.java

package com.java.feign.service;

import org.springframework.stereotype.Component;

import com.alibaba.fastjson.JSONObject;

import feign.hystrix.FallbackFactory;

@Component
public class HostServiceFallbackFactory implements FallbackFactory<HostService> {

    @Override
    public HostService create(Throwable cause) {
        return new HostService() {

            @Override
            public JSONObject getHostMessage(String id) {
                JSONObject json = new JSONObject();
                json.put("id", id);
                json.put("description", "服务异常演习专用！");
                json.put("msg", cause.getMessage());
                return json;
            }
        };
    }

}

 

6.   HostController.java

package com.java.feign.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.RestController;

import com.alibaba.fastjson.JSONObject;
import com.java.feign.service.HostService;

@RestController
public class HostController {

    @Autowired
    private HostService hostService;

    @GetMapping("/getHostMessage/{id}")
    public JSONObject getHostMessage(@PathVariable String id) {
        return hostService.getHostMessage(id);
    }

}

 

 

7.   FeignStarter.java

package com.java.feign;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.boot.builder.SpringApplicationBuilder;
import org.springframework.boot.web.servlet.support.SpringBootServletInitializer;
import org.springframework.cloud.netflix.eureka.EnableEurekaClient;
import org.springframework.cloud.openfeign.EnableFeignClients;
import org.springframework.context.annotation.ComponentScan;

@EnableEurekaClient
@SpringBootApplication
@EnableFeignClients(basePackages = { "com.java.feign.service" })
@ComponentScan(basePackages = { "com.java.feign" })
public class FeignStarter extends SpringBootServletInitializer {

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

    @Override
    protected SpringApplicationBuilder configure(SpringApplicationBuilder builder) {
        return builder.sources(FeignStarter.class);
    }

}

 

 

8.   运行测试

启动  Eureka   服务注册中心，参考  https://www.cnblogs.com/jonban/p/eureka.html

启动  MicroService  微服务， 参考   https://www.cnblogs.com/jonban/p/microservice.html

启动  Feign服务，运行 FeignStarter.java

 

浏览器输入URL

http://192.168.1.102/getHostMessage/hello

或

http://127.0.0.1/getHostMessage/hello

 

返回数据如下：

{"hostname":"F6RK2EXYAFARPPS","hostAddress":"192.168.1.102","id":"hello"}

 

截图如下：

 

搭建成功，程序正常运行。

 

下面开始测试异常

关掉微服务提供者 microservice 服务器

 

浏览器输入URL

http://192.168.1.102/getHostMessage/hello

或

http://127.0.0.1/getHostMessage/hello

 

 

返回数据如下：

{"msg":"com.netflix.client.ClientException: Load balancer does not have available server for client: MICROSERVICE","description":"服务异常演习专用！","id":"hello"}

截图如下：

 

服务异常生效，符合预期结果。