多服务间的调用-阿里云开发者社区

上文我们把我们项目注册到服务器上了，但是在微服务中，我们会有多个服务，同时也会使用A服务调用B服务的接口。springcloud netflix这里有两种方式ribbon和feign，我们分别介绍。

1.ribbon

ribbon说白了就是使用restTemplate。上文编写了被调用方的代码，下文将编写调用方的代码。

1.修改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 https://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>2.2.5.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.baocl</groupId>
    <artifactId>eureka-consumer</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>eureka-consumer</name>
    <description>Demo project for Spring Boot</description>
    <properties>
        <java.version>1.8</java.version>
        <spring-cloud.version>Hoxton.SR1</spring-cloud.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-netflix-ribbon</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-client</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
            <exclusions>
                <exclusion>
                    <groupId>org.junit.vintage</groupId>
                    <artifactId>junit-vintage-engine</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
    </dependencies>
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

2.修改Application

然后修改EurekaConsumerApplication类，需要在新建RestTemplate的bean。

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.context.annotation.Bean;
import org.springframework.web.client.RestTemplate;
@SpringBootApplication
@EnableDiscoveryClient
public class EurekaConsumerApplication {
  @Bean
  @LoadBalanced // ribbon注解
  public RestTemplate restTemplate() {
    return new RestTemplate();
  }
  public static void main(String[] args) {
    SpringApplication.run(EurekaConsumerApplication.class, args);
  }
}

3.新建调用方接口DcController

新建普通接口，调用上文被调用方的服务。

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cloud.client.discovery.DiscoveryClient;
import org.springframework.cloud.client.loadbalancer.LoadBalancerClient;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import org.springframework.web.client.RestTemplate;
@RestController
@RequestMapping("/eureka1")
public class DcController {
  @Autowired
  LoadBalancerClient loadBalancerClient;
  @Autowired
  RestTemplate restTemplate;
  @Autowired
  DiscoveryClient discoveryClient;
  @GetMapping("/consumer")
  public ResponseEntity<String> dc() {
    //String url = "http://eureka-client/aaa/dc?dk=3001";
    String url = "http://EUREKA-CLIENT/aaa/dc?dk=3001";
    System.out.println(url);
    // ServiceInstance serviceInstance =
    // loadBalancerClient.choose("eureka-client");// 获取服务提供者信息
    // // String url = "http://localhost:" + serviceInstance.getPort() + "/aaa/dc";
    // System.out.println(serviceInstance.getPort() );
    // System.out.println(url);
    // ResponseEntity r = restTemplate.getForEntity("http://eureka-client/aaa/dc",
    // String.class);
    // System.out.println("r.getHeaders().getHost():"+r.getHeaders().getHost());
    // System.out.println("r.getHeaders().getLocation():"+r.getHeaders().getLocation());
    // System.out.println("r.getHeaders().getOrigin():"+r.getHeaders().getOrigin());
    return restTemplate.getForEntity(url, String.class); // ribbon应用
  } 
}

有一个坑在调用时候需要String url = “http://eureka-client/aaa/dc?dk=3001”，而不是String url =“http://localhost:2002/aaa/dc?dk=3001”，否则会报错java.lang.IllegalStateException: No instances available for localhost.

4.修改application

最后是配置文件application.yml，这里我们使用.yml文件，都是基础配置。

eureka:
  client:
    registery-fetch-interval-seconds: 5000 
    serviceUrl:
      defaultZone: http://localhost:1001/eureka/      
eureka-client:
  ribbon:
    NFLoadBalancerRuleClassName: com.netflix.loadbalancer.RandomRule 
server:
  port: 3001
spring:
  application:
    name: eureka-consumer

输入http://localhost:3001/eureka1/consumer就可以调用到上文的client服务了，同时还可以配置负载均衡策略。在NFLoadBalancerRuleClassName: com.netflix.loadbalancer.RandomRule 处配置。

2.feign

1.修改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 https://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>2.2.5.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>
    <groupId>com.baocl</groupId>
    <artifactId>eureka-consumer-feign</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <name>eureka-consumer-feign</name>
    <description>Demo project for Spring Boot</description>
    <properties>
        <java.version>1.8</java.version>
        <spring-cloud.version>Hoxton.SR1</spring-cloud.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-netflix-eureka-client</artifactId>
        </dependency>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-feign</artifactId>
            <version>1.4.7.RELEASE</version>
        </dependency>
        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
            <exclusions>
                <exclusion>
                    <groupId>org.junit.vintage</groupId>
                    <artifactId>junit-vintage-engine</artifactId>
                </exclusion>
            </exclusions>
        </dependency>
    </dependencies>
    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>${spring-cloud.version}</version>
                <type>pom</type>
                <scope>import</scope>
            </dependency>
        </dependencies>
    </dependencyManagement>
    <build>
        <plugins>
            <plugin>
                <groupId>org.springframework.boot</groupId>
                <artifactId>spring-boot-maven-plugin</artifactId>
            </plugin>
        </plugins>
    </build>
</project>

版本问题一定要控制！！！！这里有一个坑就是版本问题，有时会报错

org.springframework.beans.factory.BeanDefinitionStoreException: Failed to read candidate component class: file [F:\workspace\springcloud\tse9\eureka-consumer-feign\target\classes\com\cloud\DcClient.class]; nested exception is org.springframework.core.annotation.AnnotationConfigurationException: Attribute 'value' in annotation [org.springframework.cloud.netflix.feign.FeignClient] must be declared as an @AliasFor 'serviceId', not 'name'.

解决办法http://www.pianshen.com/article/2239869942/

2.修改EurekaConsumerFeignApplication

首先在EurekaConsumerFeignApplication使用@EnableFeignClients中开启feign

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
import org.springframework.cloud.openfeign.EnableFeignClients;
@EnableFeignClients
@EnableDiscoveryClient
@SpringBootApplication
public class EurekaConsumerFeignApplication {
  public static void main(String[] args) {
    SpringApplication.run(EurekaConsumerFeignApplication.class, args);
  }
}

3.新建接口DcClient

新建一个接口DcClient，配置调用其他服务的名称和接口名称。（被调用方客户端的服务与接口信息）

import org.springframework.cloud.openfeign.FeignClient;
import org.springframework.web.bind.annotation.GetMapping;
@FeignClient(name = "eureka-client")
public interface DcClient {
  @GetMapping("/aaa/dc?dk=3002")
  String consumer();
  @GetMapping("/aaa/dc?dk=3002")
  String consumer2();
}

4.新建调用接口DcController

业务接口的书写，同时注入dcClient调用其他服务。

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RestController;
import com.cloud.DcClient;
@RestController
@RequestMapping("/eureka2")
public class DcController {
  @Autowired
  DcClient dcClient;
  @GetMapping("/consumer")
  public String dc() {
    return dcClient.consumer();
  }
}

5.修改application.properties

下文是最基础的配置。

spring.application.name=eureka-consumer-feign
server.port=3002
eureka.client.serviceUrl.defaultZone=http://localhost:1001/eureka/

然后调用http://localhost:3002/eureka2/consumer 可以发现接口掉通了，在被调用方也有相应的日志。

3.ribbon和Eureka整合原理

基本流程就是客户端从eureka中获取到缓存的服务列表，获取到目的服务的信息，然后通过自身的负载均衡策略，去调用对应的服务。

1.负载均衡策略

BestAvailableRule 选择一个最小的并发请求的server。
AvailabilityFilteringRule 过滤掉那些因为一直连接失败的被标记为circuit tripped的后端server，并过滤掉那些高并发的的后端server（active connections 超过配置的阈值）。
WeightedResponseTimeRule 根据响应时间分配一个weight，响应时间越长，weight越小，被选中的可能性越低。
RetryRule 对选定的负载均衡策略机上重试机制。
RoundRobinRule roundRobin方式轮询选择server.。
RandomRule 随机选择一个server。
ZoneAvoidanceRule 复合判断server所在区域的性能和server的可用性选择server。

多服务间的调用

1.ribbon

1.修改pom文件

2.修改Application

3.新建调用方接口DcController

4.修改application

2.feign

1.修改pom文件

2.修改EurekaConsumerFeignApplication

3.新建接口DcClient

4.新建调用接口DcController

5.修改application.properties

3.ribbon和Eureka整合原理

1.负载均衡策略

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