高可用服务注册中心（Eureka-Cluster）

在实际生产中，我们需要高可用的集群方案，本章就是基于SpringBoot1.5.4 Cloud（Dalston.SR2）的高可用Eureka Cluster，以及生产中需要注意的事项…

- Eureka Cluster

本教程用1个项目（battcn-cloud-discovery），多环境方式演示

- pom.xml

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

- Application.java

@SpringBootApplication
@EnableEurekaServer
public class BattcnCloudDiscoveryApplication {

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

- application.yml

server:
  port: 8761
spring:
  profiles:
    active: peer2
  #官方写的就是 8761
---
spring:
  profiles: peer1
  application:
    name: Eureka-Server-1
eureka:
  instance:
    hostname: peer1
    #配置主机名
  client:
    register-with-eureka: false
    #配置服务注册中心是否以自己为客户端进行注册(配置false)
    fetch-registry: false
    #是否取得注册信息(配置false)
    service-url:
      defaultZone: http://peer2:7002/eureka/
      #defaultZone 一定要按照标准写法，因为service-url的数据类型是Map 这算是个小坑需要注意
server:
  port: 7001
---
spring:
  profiles: peer2
  application:
    name: Eureka-Server-1
eureka:
  instance:
    hostname: peer2
    #配置主机名
  client:
    register-with-eureka: false
    #配置服务注册中心是否以自己为客户端进行注册(配置false)
    fetch-registry: false
    #是否取得注册信息(配置false)
    service-url:
      defaultZone: http://peer1:7001/eureka/
server:
  port: 7002
      #defaultZone 一定要按照标准写法，因为service-url的数据类型是Map 这算是个小坑需要注意

- 启动集群

命令：mvn clean package （先打成jar包）

1 2	peer1：java -jar battcn-cloud-discovery.jar --spring.profiles.active=peer1 peer2：java -jar battcn-cloud-discovery.jar --spring.profiles.active=peer2

1.点击蓝色加号
2.点击Spring Boot
3.填写 Name：peer1 Program arguments：–spring.profiles.active=peer1（启动2个操作2次，记得改名字和激活环境，Eclipse太简单了application.yml 直接修改内容启动就行了）

启动多个

启动成功分别访问

1	http://peer1:7001

peer1

1	http://peer2:7002

peer2

如出现上图所示，代表我们集群启动成功

- 高可用测试

1.创建battcn-cloud-h1 和 battcn-cloud-h2 2个项目，基本大同小异

就这2个包够了，跟 h1 代码唯一的区别就是 h2 做调用 h1写好接口就行了

- pom.xml

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

- application.yml

server:	
  port: 7012
spring:
  application:
    name: battcn-cloud-h2

eureka:
  instance:
    hostname: localhost #配置主机名
  client:
    service-url:
      defaultZone: http://peer1:7001/eureka/,http://peer2:7002/eureka/   #配置Eureka Server

- H2Application.java

@SpringBootApplication
@EnableDiscoveryClient
@RestController
public class H2Application {

    static Logger LOGGER = LoggerFactory.getLogger(H2Application.class);

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

    @RequestMapping("/h2")
    public String home(@RequestParam String email) {
        // 改写法之前有说过是VIP模式
        return restTemplate().getForObject("http://battcn-cloud-h1/h1?email=" + email, String.class);
    }

    public static void main(String[] args) {
        SpringApplication.run(H2Application.class, args);
    }
}

- 测试

分别启动 battcn-cloud-h1 和 battcn-cloud-h2

服务注册

访问：http://localhost:7012/h2?email=1837307557@qq.com

浏览器：My Name's :battcn-cloud-h1 Email:1837307557@qq.com 代表请求成功，然后我们断掉 peer1 或者 peer2 继续请求依旧可用，只是日志会抛异常，通过日志我们可以发现peer2 time out 因为它被杀掉了，但是这并不影响我们服务调用(高可用)，只要在启动peer2 错误就不会在出现，在生产中如果集群都挂了直接运维下岗就是了（如果peer1 peer2同时挂掉，在启动服务会自动注册上去.）

2017-07-31 23:01:03.314 ERROR 14792 --- [-target_peer2-8] c.n.e.cluster.ReplicationTaskProcessor   : Network level connection to peer peer2; retrying after delay

com.sun.jersey.api.client.ClientHandlerException: org.apache.http.conn.ConnectTimeoutException: Connect to peer2:7002 timed out
	at com.sun.jersey.client.apache4.ApacheHttpClient4Handler.handle(ApacheHttpClient4Handler.java:187) ~[jersey-apache-client4-1.19.1.jar:1.19.1]
	at com.netflix.eureka.cluster.DynamicGZIPContentEncodingFilter.handle(DynamicGZIPContentEncodingFilter.java:48) ~[eureka-core-1.6.2.jar:1.6.2]
	at com.netflix.discovery.EurekaIdentityHeaderFilter.handle(EurekaIdentityHeaderFilter.java:27) ~[eureka-client-1.6.2.jar:1.6.2]
	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.eureka.transport.JerseyReplicationClient.submitBatchUpdates(JerseyReplicationClient.java:116) ~[eureka-core-1.6.2.jar:1.6.2]
	at com.netflix.eureka.cluster.ReplicationTaskProcessor.process(ReplicationTaskProcessor.java:71) ~[eureka-core-1.6.2.jar:1.6.2]
	at com.netflix.eureka.util.batcher.TaskExecutors$BatchWorkerRunnable.run(TaskExecutors.java:187) [eureka-core-1.6.2.jar:1.6.2]
	at java.lang.Thread.run(Thread.java:745) [na:1.8.0_60]
Caused by: org.apache.http.conn.ConnectTimeoutException: Connect to peer2:7002 timed out
	at org.apache.http.conn.scheme.PlainSocketFactory.connectSocket(PlainSocketFactory.java:123) ~[httpclient-4.5.3.jar:4.5.3]
	at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:180) ~[httpclient-4.5.3.jar:4.5.3]
	at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:144) ~[httpclient-4.5.3.jar:4.5.3]
	at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:134) ~[httpclient-4.5.3.jar:4.5.3]
	at org.apache.http.impl.client.DefaultRequestDirector.tryConnect(DefaultRequestDirector.java:610) ~[httpclient-4.5.3.jar:4.5.3]
	at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:445) ~[httpclient-4.5.3.jar:4.5.3]
	at org.apache.http.impl.client.AbstractHttpClient.doExecute(AbstractHttpClient.java:835) ~[httpclient-4.5.3.jar:4.5.3]
	at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:118) ~[httpclient-4.5.3.jar:4.5.3]
	at org.apache.http.impl.client.CloseableHttpClient.execute(CloseableHttpClient.java:56) ~[httpclient-4.5.3.jar:4.5.3]
	at com.sun.jersey.client.apache4.ApacheHttpClient4Handler.handle(ApacheHttpClient4Handler.java:173) ~[jersey-apache-client4-1.19.1.jar:1.19.1]
	... 10 common frames omitted

- 注意事项

EurekaClientConfigBean.java 默认构造方法，如果serviceUrl.defaultZone = null 那么就注册到 http://localhost:8761/eureka/ 中去（日志会输出改地址，起初我是看的一脸懵逼），所以其他的Key都可以以杠(-) 或者全大写方式，该处不行，因为人家源码是Map不是对象

public EurekaClientConfigBean() {
    this.serviceUrl.put("defaultZone", "http://localhost:8761/eureka/");
    this.gZipContent = true;
    this.useDnsForFetchingServiceUrls = false;
    this.registerWithEureka = true;
    this.preferSameZoneEureka = true;
    this.availabilityZones = new HashMap();
    this.filterOnlyUpInstances = true;
    this.fetchRegistry = true;
    this.dollarReplacement = "_-";
    this.escapeCharReplacement = "__";
    this.allowRedirects = false;
    this.onDemandUpdateStatusChange = true;
    this.clientDataAccept = EurekaAccept.full.name();
}

public String[] getAvailabilityZones(String region) {
    String value = (String)this.availabilityZones.get(region);
    if(value == null) {
        value = "defaultZone";
    }

    return value.split(",");
}

public List<String> getEurekaServerServiceUrls(String myZone) {
    String serviceUrls = (String)this.serviceUrl.get(myZone);
    if(serviceUrls == null || serviceUrls.isEmpty()) {
        serviceUrls = (String)this.serviceUrl.get("defaultZone");
    }

    if(!StringUtils.isEmpty(serviceUrls)) {
        String[] serviceUrlsSplit = StringUtils.commaDelimitedListToStringArray(serviceUrls);
        List<String> eurekaServiceUrls = new ArrayList(serviceUrlsSplit.length);
        String[] var5 = serviceUrlsSplit;
        int var6 = serviceUrlsSplit.length;

        for(int var7 = 0; var7 < var6; ++var7) {
            String eurekaServiceUrl = var5[var7];
            if(!this.endsWithSlash(eurekaServiceUrl)) {
                eurekaServiceUrl = eurekaServiceUrl + "/";
            }

            eurekaServiceUrls.add(eurekaServiceUrl);
        }

        return eurekaServiceUrls;
    } else {
        return new ArrayList();
    }
}

- 小谈

其实我是比较倾向于 consul 这种零侵入式的，但是consul 在做高可用比较操蛋，它对外暴露的是 agent 如果你这个 agent挂了，那么后面服务就GG思密达了，cloud service 不允许配置多个agent，个人没找到好的解决方案，有好方案的可以交流…..