spring cloud实战之eureka服务发现

其他 2018-08-29 20:11:19 阅读次数: 0

参考spring官方文档，进行演示，link如下：

https://spring.io/guides/gs/service-registration-and-discovery/#initial


完整代码下载地址：

https://github.com/hanruikai/eureka

如有问题，可以随时联系我

1. 搭建maven环境

Pom文件如下，直接复制即可使用：

<?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>

    <groupId>com.example</groupId>
    <artifactId>eureka-service</artifactId>
    <version>0.0.1-SNAPSHOT</version>
    <packaging>jar</packaging>

    <parent>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-parent</artifactId>
        <version>2.0.3.RELEASE</version>
        <relativePath/> <!-- lookup parent from repository -->
    </parent>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <java.version>1.8</java.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.springframework.cloud</groupId>
            <artifactId>spring-cloud-starter-netflix-eureka-server</artifactId>
        </dependency>

        <dependency>
            <groupId>org.springframework.boot</groupId>
            <artifactId>spring-boot-starter-test</artifactId>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <dependencyManagement>
        <dependencies>
            <dependency>
                <groupId>org.springframework.cloud</groupId>
                <artifactId>spring-cloud-dependencies</artifactId>
                <version>Finchley.RELEASE</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>

    <repositories>
        <repository>
            <id>spring-milestones</id>
            <name>Spring Milestones</name>
            <url>https://repo.spring.io/libs-milestone</url>
            <snapshots>
                <enabled>false</enabled>
            </snapshots>
        </repository>
    </repositories>

</project>

启动类：

package hello;

import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.netflix.eureka.server.EnableEurekaServer;

@EnableEurekaServer
@SpringBootApplication
public class EurekaServiceApplication{

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

2. 启动测试

启动后发现如下异常：

2018-07-02 16:40:01.732  INFO 58338 --- [           main] o.s.c.support.DefaultLifecycleProcessor  : Starting beans in phase 0
2018-07-02 16:40:01.733  INFO 58338 --- [           main] o.s.c.n.e.s.EurekaServiceRegistry        : Registering application unknown with eureka with status UP
2018-07-02 16:40:01.733  INFO 58338 --- [           main] com.netflix.discovery.DiscoveryClient    : Saw local status change event StatusChangeEvent [timestamp=1530520801733, current=UP, previous=STARTING]
2018-07-02 16:40:01.735  INFO 58338 --- [nfoReplicator-0] com.netflix.discovery.DiscoveryClient    : DiscoveryClient_UNKNOWN/172.16.108.2: registering service...
2018-07-02 16:40:01.738  INFO 58338 --- [      Thread-13] o.s.c.n.e.server.EurekaServerBootstrap   : Setting the eureka configuration..
2018-07-02 16:40:01.739  INFO 58338 --- [      Thread-13] o.s.c.n.e.server.EurekaServerBootstrap   : Eureka data center value eureka.datacenter is not set, defaulting to default
2018-07-02 16:40:01.739  INFO 58338 --- [      Thread-13] o.s.c.n.e.server.EurekaServerBootstrap   : Eureka environment value eureka.environment is not set, defaulting to test
2018-07-02 16:40:01.743 ERROR 58338 --- [nfoReplicator-0] c.n.d.s.t.d.RedirectingEurekaHttpClient  : Request execution error

com.sun.jersey.api.client.ClientHandlerException: java.net.ConnectException: Connection refused (Connection refused)
	at com.sun.jersey.client.apache4.ApacheHttpClient4Handler.handle(ApacheHttpClient4Handler.java:187) ~[jersey-apache-client4-1.19.1.jar:1.19.1]
	at com.sun.jersey.api.client.filter.GZIPContentEncodingFilter.handle(GZIPContentEncodingFilter.java:123) ~[jersey-client-1.19.1.jar:1.19.1]
	at com.netflix.discovery.EurekaIdentityHeaderFilter.handle(EurekaIdentityHeaderFilter.java:27) ~[eureka-client-1.9.2.jar:1.9.2]
	at com.sun.jersey.api.client.Client.handle(Client.java:652) ~[jersey-client-1.19.1.jar:1.19.1]
	at com.sun.jersey.api.client.WebResource.handle(WebResource.java:682) ~[jersey-client-1.19.1.jar:1.19.1]
	at com.sun.jersey.api.client.WebResource.access$200(WebResource.java:74) ~[jersey-client-1.19.1.jar:1.19.1]
	at com.sun.jersey.api.client.WebResource$Builder.post(WebResource.java:570) ~[jersey-client-1.19.1.jar:1.19.1]
	at com.netflix.discovery.shared.transport.jersey.AbstractJerseyEurekaHttpClient.register(AbstractJerseyEurekaHttpClient.java:56) ~[eureka-client-1.9.2.jar:1.9.2]
	at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$1.execute(EurekaHttpClientDecorator.java:59) [eureka-client-1.9.2.jar:1.9.2]
	at com.netflix.discovery.shared.transport.decorator.MetricsCollectingEurekaHttpClient.execute(MetricsCollectingEurekaHttpClient.java:73) ~[eureka-client-1.9.2.jar:1.9.2]
	at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.register(EurekaHttpClientDecorator.java:56) [eureka-client-1.9.2.jar:1.9.2]
	at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$1.execute(EurekaHttpClientDecorator.java:59) [eureka-client-1.9.2.jar:1.9.2]
	at com.netflix.discovery.shared.transport.decorator.RedirectingEurekaHttpClient.executeOnNewServer(RedirectingEurekaHttpClient.java:118) ~[eureka-client-1.9.2.jar:1.9.2]
	at com.netflix.discovery.shared.transport.decorator.RedirectingEurekaHttpClient.execute(RedirectingEurekaHttpClient.java:79) ~[eureka-client-1.9.2.jar:1.9.2]
	at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.register(EurekaHttpClientDecorator.java:56) [eureka-client-1.9.2.jar:1.9.2]
	at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$1.execute(EurekaHttpClientDecorator.java:59) [eureka-client-1.9.2.jar:1.9.2]
	at com.netflix.discovery.shared.transport.decorator.RetryableEurekaHttpClient.execute(RetryableEurekaHttpClient.java:120) [eureka-client-1.9.2.jar:1.9.2]
	at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.register(EurekaHttpClientDecorator.java:56) [eureka-client-1.9.2.jar:1.9.2]
	at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator$1.execute(EurekaHttpClientDecorator.java:59) [eureka-client-1.9.2.jar:1.9.2]
	at com.netflix.discovery.shared.transport.decorator.SessionedEurekaHttpClient.execute(SessionedEurekaHttpClient.java:77) [eureka-client-1.9.2.jar:1.9.2]
	at com.netflix.discovery.shared.transport.decorator.EurekaHttpClientDecorator.register(EurekaHttpClientDecorator.java:56) [eureka-client-1.9.2.jar:1.9.2]
	at com.netflix.discovery.DiscoveryClient.register(DiscoveryClient.java:829) [eureka-client-1.9.2.jar:1.9.2]
	at com.netflix.discovery.InstanceInfoReplicator.run(InstanceInfoReplicator.java:121) [eureka-client-1.9.2.jar:1.9.2]
	at com.netflix.discovery.InstanceInfoReplicator$1.run(InstanceInfoReplicator.java:101) [eureka-client-1.9.2.jar:1.9.2]
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511) [na:1.8.0_151]
	at java.util.concurrent.FutureTask.run(FutureTask.java:266) [na:1.8.0_151]
	at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$201(ScheduledThreadPoolExecutor.java:180) [na:1.8.0_151]
	at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:293) [na:1.8.0_151]
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) [na:1.8.0_151]
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) [na:1.8.0_151]
	at java.lang.Thread.run(Thread.java:748) [na:1.8.0_151]
Caused by: java.net.ConnectException: Connection refused (Connection refused)
	at java.net.PlainSocketImpl.socketConnect(Native Method) ~[na:1.8.0_151]
	at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350) ~[na:1.8.0_151]
	at java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206) ~[na:1.8.0_151]
	at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188) ~[na:1.8.0_151]
	at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392) ~[na:1.8.0_151]
	at java.net.Socket.connect(Socket.java:589) ~[na:1.8.0_151]
	at org.apache.http.conn.scheme.PlainSocketFactory.connectSocket(PlainSocketFactory.java:121) ~[httpclient-4.5.5.jar:4.5.5]
	at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:180) ~[httpclient-4.5.5.jar:4.5.5]
	at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:144) ~[httpclient-4.5.5.jar:4.5.5]
	at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:134) ~[httpclient-4.5.5.jar:4.5.5]
	at org.apache.http.impl.client.DefaultRequestDirector.tryConnect(DefaultRequestDirector.java:610) ~[httpclient-4.5.5.jar:4.5.5]
	at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:445) ~[httpclient-4.5.5.jar:4.5.5]
	at org.apache.http.impl.client.AbstractHttpClient.doExecute(AbstractHttpClient.java:835) ~[httpclient-4.5.5.jar:4.5.5]
	at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:118) ~[httpclient-4.5.5.jar:4.5.5]
	at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:56) ~[httpclient-4.5.5.jar:4.5.5]
	at com.sun.jersey.client.apache4.ApacheHttpClient4Handler.handle(ApacheHttpClient4Handler.java:173) ~[jersey-apache-client4-1.19.1.jar:1.19.1]
	... 30 common frames omitted

* 查资料发现，说eureka会自动注册自己，必须设置下面属性

扫描二维码关注公众号，回复： 2947153 查看本文章 
eureka.client.register-with-eureka=false
eureka.client.fetch-registry=false

但是发现已经设置过，但是属性颜色为灰色，怀疑没有生效，可能工程搭建问题，重新搭建工程，ok

*Eureka client启动后自动关闭，看日志进行过注册，但是后来又取消注册，查资料发现增加依赖

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>

增加依赖后解决，否则eureka client会自动退出，并且不报错

3. GUI显示

打开eureka注册中心管理页面

http://localhost:8761/


能够看到client已经进行了注册，注册信息如上图所示


打开client的endpoint地址

http://localhost:8080/service-instances/a-bootiful-client

返回结果如下：


4 配置中心

上面的例子完全可以运行，问题是并没有配置注册中心的地址，但是client却能够成功注册，发现client的配置文件可以配置注册中心地址，配置如下：

spring.application.name=a-bootiful-client
eureka.client.service-url.defaultZone=http://localhost:8761/eureka

配置后启动，正常。

5. 服务调用测试

写了一个测试类，在client工程中，计划调用provider的接口，我们一起来试试：

测试类代码如下：

package hello;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.context.annotation.Bean;
import org.springframework.http.HttpMethod;
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 org.springframework.web.client.RestTemplate;

import java.util.List;

/**
 * Created by hanruikai on 2018/7/3.
 */


@RestController
@RequestMapping("/api/v1/")
class TestController {

    @Autowired
    private RestTemplate restTemplate;

    @GetMapping("testinvoke")
    public List<ServiceInstance> serviceInstancesByApplicationName() {
        restTemplate.exchange("http://A-BOOTIFUL-CLIENT/test",HttpMethod.GET,null,String.class);
        return null;
    }

    @Bean
    @LoadBalanced
    public RestTemplate restTemplate() {
        return new RestTemplate();
    }
}

用postman测试，发现错误如下：

{
    "timestamp": "2018-07-03T03:09:27.374+0000",
    "status": 500,
    "error": "Internal Server Error",
    "message": "No instances available for A-BOOTIFUL-CLIENT",
    "path": "/api/v1/testinvoke"
}

原来是application name后来修改了，不是原来的bootiful client。

spring.application.name=service-consume
eureka.client.service-url.defaultZone=http://localhost:8761/eureka
spring.application.name=service-provider
eureka.client.service-url.defaultZone=http://localhost:8761/eureka
Application AMIs Availability Zones Status
SERVICE-CONSUME n/a (1) (1) UP (1) - 172.16.104.15:service-consume
SERVICE-PROVIDER n/a (1) (1) UP (1) - 172.16.104.15:service-provider:8099

修改成功的测试类如下：

package hello;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.loadbalancer.LoadBalanced;
import org.springframework.context.annotation.Bean;
import org.springframework.http.HttpMethod;
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 org.springframework.web.client.RestTemplate;

import java.util.List;

/**
 * Created by hanruikai on 2018/7/3.
 */


@RestController
@RequestMapping("/api/v1/")
class TestController {

    @Autowired
    private RestTemplate restTemplate;

    @GetMapping("testinvoke")
    public List<ServiceInstance> serviceInstancesByApplicationName() {
        restTemplate.exchange("http://SERVICE-PROVIDER/test",HttpMethod.GET,null,String.class);
        return null;
    }

    @Bean
    @LoadBalanced
    public RestTemplate restTemplate() {
        return new RestTemplate();
    }
}

服务调用方启动类@loadbalance，日志如下

2018-07-03 11:15:10.805  INFO 60148 --- [nio-8080-exec-1] c.netflix.loadbalancer.BaseLoadBalancer  : Client: SERVICE-PROVIDER instantiated a LoadBalancer: DynamicServerListLoadBalancer:{NFLoadBalancer:name=SERVICE-PROVIDER,current list of Servers=[],Load balancer stats=Zone stats: {},Server stats: []}ServerList:null
2018-07-03 11:15:10.811  INFO 60148 --- [nio-8080-exec-1] c.n.l.DynamicServerListLoadBalancer      : Using serverListUpdater PollingServerListUpdater
2018-07-03 11:15:10.832  INFO 60148 --- [nio-8080-exec-1] c.netflix.config.ChainedDynamicProperty  : Flipping property: SERVICE-PROVIDER.ribbon.ActiveConnectionsLimit to use NEXT property: niws.loadbalancer.availabilityFilteringRule.activeConnectionsLimit = 2147483647
2018-07-03 11:15:10.834  INFO 60148 --- [nio-8080-exec-1] c.n.l.DynamicServerListLoadBalancer      : DynamicServerListLoadBalancer for client SERVICE-PROVIDER initialized: DynamicServerListLoadBalancer:{NFLoadBalancer:name=SERVICE-PROVIDER,current list of Servers=[172.16.104.15:8099],Load balancer stats=Zone stats: {defaultzone=[Zone:defaultzone; Instance count:1; Active connections count: 0; Circuit breaker tripped count: 0; Active connections per server: 0.0;]
},Server stats: [[Server:172.16.104.15:8099; Zone:defaultZone; Total Requests:0; Successive connection failure:0; Total blackout seconds:0; Last connection made:Thu Jan 01 08:00:00 CST 1970; First connection made: Thu Jan 01 08:00:00 CST 1970; Active Connections:0; total failure count in last (1000) msecs:0; average resp time:0.0; 90 percentile resp time:0.0; 95 percentile resp time:0.0; min resp time:0.0; max resp time:0.0; stddev resp time:0.0]
]}ServerList:org.springframework.cloud.netflix.ribbon.eureka.DomainExtractingServerList@485b2cbe
2018-07-03 11:15:11.819  INFO 60148 --- [erListUpdater-0] c.netflix.config.ChainedDynamicProperty  : Flipping property: SERVICE-PROVIDER.ribbon.ActiveConnectionsLimit to use NEXT property: niws.loadbalancer.availabilityFilteringRule.activeConnectionsLimit = 2147483647

服务提供方的日志如下：

2018-07-03 11:17:24.495  INFO 60163 --- [nio-8099-exec-1] o.s.web.servlet.DispatcherServlet        : FrameworkServlet 'dispatcherServlet': initialization completed in 12 ms

invoked successfully


代码：

package hello;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.SpringApplication;
import org.springframework.boot.autoconfigure.SpringBootApplication;
import org.springframework.cloud.client.ServiceInstance;
import org.springframework.cloud.client.discovery.DiscoveryClient;
import org.springframework.cloud.client.discovery.EnableDiscoveryClient;
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 java.util.List;

@EnableDiscoveryClient
@SpringBootApplication
public class EurekaProviderApplication {

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

@RestController
class ServiceInstanceRestController {


    @GetMapping("/test")
    public void test() {
        System.out.print("invoked successfully");
    }
}

6 总结

*每个服务注册到eureka，都是client端，注册后application name用来区分一组应用，应该是同一个application name到服务进行负载均衡

*负载均衡不需要借助dns server ，注册服务利用心跳与eureka通信，超过一定时间被移除

*Eureka利用rest交互，不同于dubbo，利用RPC通信

*Eureka在CAP中，选择了AP，而zookeep选择到是CP

*Eureka与spring boot进行了很好的集成

*Eureka集群节点进行副本复制，而且client进行缓存，即使所有到eureka节点挂掉，服务也可用

*Spring cloud强大到生态体系

集群中的的不同服务注册中心通过异步模式互相复制各自的状态，这也意味着在给定的时间点每个实例关于所有服务的状态可能存在不一致的现象（CAP理论中，Eureka选择了AP，作为注册中心可用性比一致性重要）

在服务治理框架中，通常都会构建一个注册中心，每个服务单元向注册中心登记自己提供的服务，包括服务的主机与端口号、服务版本号、通讯协议等一些附加信息。注册中心按照服务名分类组织服务清单，同时还需要以心跳检测的方式去监测清单中的服务是否可用，若不可用需要从服务清单中剔除，以达到排除故障服务的效果

在服务治理框架下，服务间的调用不再通过指定具体的实例地址来实现，而是通过服务名发起请求调用实现。服务调用方通过服务名从服务注册中心的服务清单中获取服务实例的列表清单，通过指定的负载均衡策略取出一个服务实例位置来进行服务调用。

在应用程序启动时，Eureka客户端向服务注册中心注册自身提供的服务，并周期性的发送心跳来更新它的服务租约。同时，他也能从服务端查询当前注册的服务信息并把它们缓存到本地并周期行的刷新服务状态。


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