多服務間的調用

上文我們把我們項目注冊到伺服器上了，但是在微服務中，我們會有多個服務，同時也會使用A服務調用B服務的接口。springcloud netflix這裡有兩種方式ribbon和feign，我們分别介紹。

1.ribbon

ribbon說白了就是使用restTemplate。上文編寫了被調用方的代碼，下文将編寫調用方的代碼。

1.修改pom檔案

<?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

然後修改EurekaConsumerApplication類，需要在建立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.建立調用方接口DcController

建立普通接口，調用上文被調用方的服務。

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");// 擷取服務提供者資訊
        // // 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應用
    }   
}

有一個坑在調用時候需要String url = “http://eureka-client/aaa/dc?dk=3001”，而不是String url =“http://localhost:2002/aaa/dc?dk=3001”，否則會報錯java.lang.IllegalStateException: No instances available for localhost.

4.修改application

最後是配置檔案application.yml，這裡我們使用.yml檔案，都是基礎配置。

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

輸入http://localhost:3001/eureka1/consumer就可以調用到上文的client服務了，同時還可以配置負載均衡政策。在NFLoadBalancerRuleClassName: com.netflix.loadbalancer.RandomRule 處配置。

2.feign

<?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>

版本問題一定要控制！！！！這裡有一個坑就是版本問題，有時會報錯

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'.

解決辦法

http://www.pianshen.com/article/2239869942/

2.修改EurekaConsumerFeignApplication

首先在EurekaConsumerFeignApplication使用@EnableFeignClients中開啟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.建立接口DcClient

建立一個接口DcClient，配置調用其他服務的名稱和接口名稱。（被調用方用戶端的服務與接口資訊）

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.建立調用接口DcController

業務接口的書寫，同時注入dcClient調用其他服務。

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

下文是最基礎的配置。

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

然後調用http://localhost:3002/eureka2/consumer 可以發現接口掉通了，在被調用方也有相應的日志。

3.ribbon和Eureka整合原理

基本流程就是用戶端從eureka中擷取到緩存的服務清單，擷取到目的服務的資訊，然後通過自身的負載均衡政策，去調用對應的服務。

1.負載均衡政策

BestAvailableRule 選擇一個最小的并發請求的server。
AvailabilityFilteringRule 過濾掉那些因為一直連接配接失敗的被标記為circuit tripped的後端server，并過濾掉那些高并發的的後端server（active connections 超過配置的門檻值）。
WeightedResponseTimeRule 根據響應時間配置設定一個weight，響應時間越長，weight越小，被選中的可能性越低。
RetryRule 對標明的負載均衡政策機上重試機制。
RoundRobinRule roundRobin方式輪詢選擇server.。
RandomRule 随機選擇一個server。
ZoneAvoidanceRule 複合判斷server所在區域的性能和server的可用性選擇server。

多服務間的調用

1.ribbon

1.修改pom檔案

2.修改Application

3.建立調用方接口DcController

4.修改application

2.feign

2.修改EurekaConsumerFeignApplication

3.建立接口DcClient

4.建立調用接口DcController

5.修改application.properties

3.ribbon和Eureka整合原理

1.負載均衡政策

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