zookeeper负载均衡

最新推荐文章于 2022-01-09 14:55:26 发布

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最新推荐文章于 2022-01-09 14:55:26 发布

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文章标签： java 大数据 web.xml

原文链接：http://www.cnblogs.com/liaomin416100569/p/9331220.html

本文介绍如何利用Alibaba的Dubbo框架结合WebService实现负载均衡。通过在多个服务器上部署相同的服务，并利用Zookeeper进行服务注册与发现，客户端能够智能地选择压力较小的服务器进行请求，有效分散负载。

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一负载均衡原理

负载均衡为将应用的并发处理能力分摊到不同的机器中机器上水平分布着相同功能的应用，实现负载均衡需要考虑到服务器的容灾能力，服务器的动态配置等

实现场景：

假设在服务端存在一个webservice 部署在58.131，58.132上客户端每次访问压力最小的服务器

从零开发需要当服务器58.131和58.132启动时要在zookooper集群中注册临时节点客户端订阅zookeeper该临时节点客户端使用负载均衡算法当访问服务器开始时修改zookeeper上该服务器节点的值累加1 完成访问后减1实现相对复杂

Alibaba的dubbo框架实现了在zokeeper自动注册服务器客户端自动订阅和缓存数据以及负载均衡算法的功能这里使用maven来添加dubbo和webservice依赖 dubbo必须依靠spring来进行管理

服务端代码

webservice接口

package cn.et.dubbo;

public interface DemoService {
	public String sayHello(String name);
}

实现类

 package cn.et.dubbo;

public class DemoServiceImpl implements DemoService {
	public String sayHello(String name) {
        return "Hello " + name;
    }
 
}

Spring配置文件

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
	xmlns:dubbo="http://code.alibabatech.com/schema/dubbo"
	xsi:schemaLocation="
    http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.0.xsd
    http://code.alibabatech.com/schema/dubbo http://code.alibabatech.com/schema/dubbo/dubbo.xsd
    ">
	<!-- 提供方应用信息，用于计算依赖关系 name就是项目名称 -->
	<dubbo:application name="uuid" />
<!--注册服务器 当该服务启动时 自动将服务器信息写入 zookeeper服务器中 
   如果是zookeeper集群 address用逗号隔开
-->
    <dubbo:registry address="192.168.58.1:2181"  protocol="zookeeper" session="5000" timeout="1">
    </dubbo:registry>
    <!-- port和tomcat的端口必须一致  web.xml配置的servlet拦截的/*
       访问都中http://当前ip:8080/上下文路径/cn.et.dubbo.DemoService?wsdl
     -->
    <dubbo:protocol name="webservice" port="8080" server="servlet" />
	<!-- 声明需要暴露的服务接口 -->
	<dubbo:service interface="cn.et.dubbo.DemoService"  protocol="webservice" 
		ref="demoService"  />
    <bean id="demoService" class="cn.et.dubbo.DemoServiceImpl"></bean>
	
    
</beans>

Web.xml配置

       <context-param>
		<param-name>contextConfigLocation</param-name>
		<param-value>classpath:/spring.xml</param-value>
       </context-param>
	
        <!--spring的配置-->
	<listener>
		<listener-class>org.springframework.web.context.ContextLoaderListener</listener-class>
	</listener>
	<servlet>
		<servlet-name>dubbo</servlet-name>
		<servlet-class>com.alibaba.dubbo.remoting.http.servlet.DispatcherServlet</servlet-class>
		<load-on-startup>1</load-on-startup>
	</servlet>
	<servlet-mapping>
		<servlet-name>dubbo</servlet-name>
		<url-pattern>/*</url-pattern>
	</servlet-mapping>

maven添加依赖

                <dependency>
			<groupId>org.springframework</groupId>
			<artifactId>spring-webmvc</artifactId>
			<version>4.0.0.RELEASE</version>
		</dependency>
		<dependency>
			<groupId>com.alibaba</groupId>
			<artifactId>dubbo</artifactId>
			<version>2.4.7</version>
			<exclusions>
				<exclusion>
					<artifactId>spring</artifactId>
					<groupId>org.springframework</groupId>
				</exclusion>
			</exclusions>
		</dependency>
		<dependency>
			<groupId>org.apache.cxf</groupId>
			<artifactId>cxf-rt-frontend-simple</artifactId>
			<version>2.6.1</version>
		</dependency>
		<dependency>
			<groupId>org.apache.cxf</groupId>
			<artifactId>cxf-rt-transports-http</artifactId>
			<version>2.6.1</version>
		</dependency>
		<dependency>
			<groupId>org.eclipse.jetty</groupId>
			<artifactId>jetty-server</artifactId>
			<version>9.3.0.M2</version>
		</dependency>

		<dependency>
			<groupId>com.github.sgroschupf</groupId>
			<artifactId>zkclient</artifactId>
			<version>0.1</version>
		</dependency>

以上程序部署到 58.131,58.132的tomcat中运行zkcli查看 /duddo节点下的子节点信息

有时在linux启动时会抛出异常 bogon: bogon: Name or service not known, dubbo version: 2.4.7, current host:

因为dubbo尝试获取linux主机名后获取对应的主机ip

使用命令 hostname查看主机名为bogon

修改 /etc/hosts添加一行

bogon 当前主机的ip

比如 58.131机器上添加 bogon 192.168.58.131

启动后访问

http://192.168.58.131:8080/uuid/cn.et.dubbo.DemoService?wsdl

http://192.168.58.132:8080/uuid/cn.et.dubbo.DemoService?wsdl

使用zkcli客户端查看zookeeper注册中心注册信息

[zk: 192.168.58.1:2181(CONNECTED) 258] ls /dubbo/cn.et.dubbo.DemoService/providers
[webservice%3A%2F%2F192.168.58.132%3A8080%2Fcn.et.dubbo.DemoService%3Fanyhost%3D
true%26application%3Duuid%26dubbo%3D2.4.7%26interface%3Dcn.et.dubbo.DemoService%
26methods%3DsayHello%26pid%3D4664%26server%3Dservlet%26side%3Dprovider%26timesta
mp%3D1495539889340, webservice%3A%2F%2F192.168.58.131%3A8080%2Fcn.et.dubbo.DemoS
ervice%3Fanyhost%3Dtrue%26application%3Duuid%26dubbo%3D2.4.7%26interface%3Dcn.et
.dubbo.DemoService%26methods%3DsayHello%26pid%3D4494%26server%3Dservlet%26side%3
Dprovider%26timestamp%3D1495539894062]
[zk: localhost:2181(CONNECTED) 259]

【注意点1】

<dubbo:registry address="192.168.58.1:2181" protocol="zookeeper" session="5000" timeout="1">

这里设置的session超时时间和连接timeout 都是无效的需要自己重写部分api

在dubbojar包 dubbo/internal/com.alibaba.dubbo.remoting.zookeeper.ZookeeperTrasporter资源文件里面定义了使用不同客户端调用zookeer的代码

里面有使用zkclient和curator的代码

zkclient=com.alibaba.dubbo.remoting.zookeeper.zkclient.ZkclientZookeeperTransporter

我们在自己的项目中新建一个相同的类代码拷贝相同

package cn.et.dubbo;

import com.alibaba.dubbo.common.URL;
import com.alibaba.dubbo.remoting.zookeeper.ZookeeperClient;
import com.alibaba.dubbo.remoting.zookeeper.ZookeeperTransporter;


public class ZkclientZookeeperTransporter implements ZookeeperTransporter {

	public ZookeeperClient connect(URL url) {
		return new ZkclientZookeeperClient(url);
	}

}

重写 ZkclientZookeeperClient类

package cn.et.dubbo;

import java.util.List;

import org.I0Itec.zkclient.IZkChildListener;
import org.I0Itec.zkclient.IZkStateListener;
import org.I0Itec.zkclient.ZkClient;
import org.I0Itec.zkclient.exception.ZkNoNodeException;
import org.I0Itec.zkclient.exception.ZkNodeExistsException;
import org.apache.zookeeper.Watcher.Event.KeeperState;

import com.alibaba.dubbo.common.URL;
import com.alibaba.dubbo.remoting.zookeeper.ChildListener;
import com.alibaba.dubbo.remoting.zookeeper.StateListener;
import com.alibaba.dubbo.remoting.zookeeper.support.AbstractZookeeperClient;

public class ZkclientZookeeperClient  extends AbstractZookeeperClient<IZkChildListener>  {

	private final ZkClient client;

	private volatile KeeperState state = KeeperState.SyncConnected;

	public ZkclientZookeeperClient(URL url) {
		super(url);

                //默认的代码是client = new ZkClient(url.getBackupAddress())

		client = new ZkClient(url.getBackupAddress(),5000,1000);//这里自己设置这个超时和连接时间
		client.subscribeStateChanges(new IZkStateListener() {
			public void handleStateChanged(KeeperState state) throws Exception {
				ZkclientZookeeperClient.this.state = state;
				if (state == KeeperState.Disconnected) {
					stateChanged(StateListener.DISCONNECTED);
				} else if (state == KeeperState.SyncConnected) {
					stateChanged(StateListener.CONNECTED);
				}
			}
			public void handleNewSession() throws Exception {
				stateChanged(StateListener.RECONNECTED);
			}
		});
	}

	public void createPersistent(String path) {
		try {
			client.createPersistent(path, true);
		} catch (ZkNodeExistsException e) {
		}
	}

	public void createEphemeral(String path) {
		try {
			/*
				这里  %2F为 /  重写添加上下文路径  
				也就是/cn.et.dubbo.DemoService 替换为 /uuid/cn.et.dubbo.DemoService
				订阅者 从 zookeeper中获取可以访问的服务器webservice地址  注册时不会添加上下文路径 所以我们
				需要添加上下文路径 才能正常调用
				如果在提供者 spring.xml中添加 
				<dubbo:protocol name="webservice" port="8080" server="servlet" path="uuid"/>
				dubbo在上下文路径后在加上一层 uuid
				访问编程了 http://localhost:8080/uuid/uuid/cn.et.dubbo.DemoService?wsdl
			 * */
			if(path.indexOf("%2Fcn.et.dubbo.DemoService")>0){
				path=path.replaceAll("%2Fcn.et.dubbo.DemoService", "%2Fuuid%2Fcn.et.dubbo.DemoService");
			}
			client.createEphemeral(path);
		} catch (ZkNodeExistsException e) {
		}
	}

	public void delete(String path) {
		try {
			client.delete(path);
		} catch (ZkNoNodeException e) {
		}
	}

	public List<String> getChildren(String path) {
		try {
			return client.getChildren(path);
        } catch (ZkNoNodeException e) {
            return null;
        }
	}

	public boolean isConnected() {
		return state == KeeperState.SyncConnected;
	}

	public void doClose() {
		client.close();
	}

	public IZkChildListener createTargetChildListener(String path, final ChildListener listener) {
		return new IZkChildListener() {
			public void handleChildChange(String parentPath, List<String> currentChilds)
					throws Exception {
				listener.childChanged(parentPath, currentChilds);
			}
		};
	}

	public List<String> addTargetChildListener(String path, final IZkChildListener listener) {
		return client.subscribeChildChanges(path, listener);
	}

	public void removeTargetChildListener(String path, IZkChildListener listener) {
		client.unsubscribeChildChanges(path,  listener);
	}

}

修改完成将编译好的类添加到jar包中修改jar包中dubbo/internal/com.alibaba.dubbo.remoting.zookeeper.ZookeeperTrasporter文件

zkclient=cn.et.dubbo。ZkclientZookeeperTransporter

【注意点2】实际访问地址为192.168.58.132:8080//uuid/cn.et.dubbo.DemoService?wsdl 前面带了上下文路径

zookeeper中注册的确实192.168.58.132:8080/cn.et.dubbo.DemoService 订阅者（客户端）获取这个地址肯定无法调用（上面ZkclientZookeeperClient类

createEphemeral标红的部分就解决了 上下文路径注册的问题

）

客户端调用的配置

spring.xml

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans"
	xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" 
	xmlns:dubbo="http://code.alibabatech.com/schema/dubbo"
	xsi:schemaLocation="
    http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans-4.0.xsd
    http://code.alibabatech.com/schema/dubbo http://code.alibabatech.com/schema/dubbo/dubbo.xsd
    ">
	<!-- 提供方应用信息，用于计算依赖关系 -->
	<dubbo:application name="uuid" />
    <dubbo:registry address="192.168.58.1:2181"  protocol="zookeeper" session="5000" timeout="1" >
    </dubbo:registry>
	<!-- 声明需要暴露的服务接口 -->
	<dubbo:reference interface="cn.et.dubbo.DemoService" id="mydemo"  >
	</dubbo:reference>
    
</beans>

pom.xml 依赖和服务器端一致

java调用代码

package cn.et.dubbo;

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class Provider {

	/**
	 *时间：2017-5-25 下午08:20:17
	 *作者： LM
	 *联系方式：973465719@qq.com
	 * @param args
	 */
	public static void main(String[] args) throws Exception {
        ClassPathXmlApplicationContext context = new ClassPathXmlApplicationContext(new String[] {"/spring.xml"});
        DemoService demo=(DemoService)context.getBean("mydemo");
        System.out.println(demo.sayHello("jiaozi"));
        System.in.read(); // 按任意键退出
    }

}

此时交换停止 58.131和 58.132 运行客户端main方法测试webservice是否能够调用我这里正常调用

转载于:https://www.cnblogs.com/liaomin416100569/p/9331220.html