• zookeeper学习【6】负载均衡


    负载均衡是一种手段,用来把对某种资源的访问分摊给不同的设备,从而减轻单点的压力。

    架构图

    图中左侧为ZooKeeper集群,右侧上方为工作服务器,下面为客户端。每台工作服务器在启动时都会去zookeeper的servers节点下注册临时节点,每台客户端在启动时都会去servers节点下取得所有可用的工作服务器列表,并通过一定的负载均衡算法计算得出一台工作服务器,并与之建立网络连接。网络连接我们采用开源框架netty。

    流程图

    负载均衡客户端流程

     

    服务端主体流程

     

    类图

    Server端核心类


    每个服务端对应一个Server接口,ServiceImpl是服务端的实现类。把服务端启动时的注册过程抽出为一个接口RegistProvider,并给予一个默认实现DefaultRegistProvider,它将用到一个上下文的类ZooKeeperRegistContext。我们的服务端是给予Netty的,它需要ServerHandler来处理与客户端之间的连接,当有客户端建立或失去连接时,我们都需要去修改当前服务器的负载信息,我们把修改负载信息的过程也抽出为一个接口BalanceUpdateProvider,并且给予了一个默认实现DefaultBalanceUpdateProvider。ServerRunner是调度类,负责调度我们的Server。

    Client端核心类


    每个客户端都需要实现一个Client接口,ClientImpl是实现,Client需要ClientHandler来处理与服务器之前的通讯,同时它需要BalanceProvider为它提供负载均衡的算法。BalanceProvider是接口,它有2个实现类,一个是抽象的实现AbstractBalanceProvider,一个是默认的实现DefaultBalanceProvider。ServerData是服务端和客户端共用的一个类,服务端会把自己的基本信息,包括负载信息,打包成ServerData并写入到zookeeper中,客户端在计算负载的时候需要到zookeeper中拿到ServerData,并取得服务端的地址和负载信息。ClientRunner是客户端的调度类,负责启动客户端。

    服务端代码:

    public interface BalanceUpdateProvider {
    
        // 增加负载
        public boolean addBalance(Integer step);
    
        // 减少负载
        public boolean reduceBalance(Integer step);
    
    }
    package com.test.cbd.zookeeper.loadbalance;
    
    import org.I0Itec.zkclient.ZkClient;
    import org.I0Itec.zkclient.exception.ZkBadVersionException;
    import org.apache.zookeeper.data.Stat;
    
    public class DefaultBalanceUpdateProvider implements BalanceUpdateProvider {
    
        private String serverPath;
        private ZkClient zc;
    
        public DefaultBalanceUpdateProvider(String serverPath, ZkClient zkClient) {
            this.serverPath = serverPath;
            this.zc = zkClient;
        }
    
        public boolean addBalance(Integer step) {
            Stat stat = new Stat();
            ServerData sd;
    
            // 增加负载:读取服务器的信息ServerData,增加负载,并写回zookeeper
            while (true) {
                try {
                    sd = zc.readData(this.serverPath, stat);
                    sd.setBalance(sd.getBalance() + step);
                    // 带上版本,因为可能有其他客户端连接到服务器修改了负载
                    zc.writeData(this.serverPath, sd, stat.getVersion());
                    return true;
                } catch (ZkBadVersionException e) {
                    // ignore
                } catch (Exception e) {
                    return false;
                }
            }
    
        }
    
        public boolean reduceBalance(Integer step) {
            Stat stat = new Stat();
            ServerData sd;
    
            while (true) {
                try {
                    sd = zc.readData(this.serverPath, stat);
                    final Integer currBalance = sd.getBalance();
                    sd.setBalance(currBalance>step?currBalance-step:0);
                    zc.writeData(this.serverPath, sd, stat.getVersion());
                    return true;
                } catch (ZkBadVersionException e) {
                    // ignore
                } catch (Exception e) {
                    return false;
                }
            }
        }
    
    }
    package com.test.cbd.zookeeper.loadbalance;
    
    import org.I0Itec.zkclient.ZkClient;
    import org.I0Itec.zkclient.exception.ZkNoNodeException;
    
    public class DefaultRegistProvider implements RegistProvider {
    
        // 在zookeeper中创建临时节点并写入信息
        public void regist(Object context) throws Exception {
    
            // Server在zookeeper中注册自己,需要在zookeeper的目标节点上创建临时节点并写入自己
            // 将需要的以下3个信息包装成上下文传入
            // 1:path
            // 2:zkClient
            // 3:serverData
    
            ZooKeeperRegistContext registContext = (ZooKeeperRegistContext) context;
            String path = registContext.getPath();
            ZkClient zc = registContext.getZkClient();
    
            try {
                zc.createEphemeral(path, registContext.getData());
            } catch (ZkNoNodeException e) {
                String parentDir = path.substring(0, path.lastIndexOf('/'));
                zc.createPersistent(parentDir, true);
                regist(registContext);
            }
        }
    
        public void unRegist(Object context) throws Exception {
            return;
        }
    
    }
    package com.test.cbd.zookeeper.loadbalance;
    
    public interface RegistProvider {
    
        public void regist(Object context) throws Exception;
    
        public void unRegist(Object context) throws Exception;
    }
    package com.test.cbd.zookeeper.loadbalance;
    
    public interface Server {
    
        public void bind();
    }
    package com.test.cbd.zookeeper.loadbalance;
    
    import java.io.Serializable;
    
    public class ServerData implements Serializable,Comparable<ServerData> {
    
        private static final long serialVersionUID = -8892569870391530906L;
    
    
        private Integer balance;
        private String host;
        private Integer port;
    
    
        public Integer getBalance() {
            return balance;
        }
        public void setBalance(Integer balance) {
            this.balance = balance;
        }
        public String getHost() {
            return host;
        }
        public void setHost(String host) {
            this.host = host;
        }
        public Integer getPort() {
            return port;
        }
        public void setPort(Integer port) {
            this.port = port;
        }
    
    
        @Override
        public String toString() {
            return "ServerData [balance=" + balance + ", host=" + host + ", port="
                    + port + "]";
        }
        public int compareTo(ServerData o) {
            return this.getBalance().compareTo(o.getBalance());
        }
    
    }
    package com.test.cbd.zookeeper.loadbalance;
    
    import io.netty.channel.ChannelHandlerAdapter;
    import io.netty.channel.ChannelHandlerContext;
    
    /**
     * 处理服务端与客户端之间的通信
     */
    public class ServerHandler extends ChannelHandlerAdapter {
    
        private final BalanceUpdateProvider balanceUpdater;
        private static final Integer BALANCE_STEP = 1;
    
    
        public ServerHandler(BalanceUpdateProvider balanceUpdater){
            this.balanceUpdater = balanceUpdater;
    
        }
    
        public BalanceUpdateProvider getBalanceUpdater() {
            return balanceUpdater;
        }
    
        // 建立连接时增加负载
        @Override
        public void channelActive(ChannelHandlerContext ctx) throws Exception {
            System.out.println("one client connect...");
            balanceUpdater.addBalance(BALANCE_STEP);
        }
    
        // 断开连接时减少负载
        @Override
        public void channelInactive(ChannelHandlerContext ctx) throws Exception {
            balanceUpdater.reduceBalance(BALANCE_STEP);
        }
    
        @Override
        public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
            cause.printStackTrace();
            ctx.close();
        }
    
    
    }
    package com.test.cbd.zookeeper.loadbalance;
    
    import io.netty.bootstrap.ServerBootstrap;
    import io.netty.channel.*;
    import io.netty.channel.nio.NioEventLoopGroup;
    import io.netty.channel.socket.SocketChannel;
    import io.netty.channel.socket.nio.NioServerSocketChannel;
    import org.I0Itec.zkclient.ZkClient;
    import org.I0Itec.zkclient.serialize.SerializableSerializer;
    
    
    public class ServerImpl implements Server {
    
        private EventLoopGroup bossGroup = new NioEventLoopGroup();
        private EventLoopGroup workGroup = new NioEventLoopGroup();
        private ServerBootstrap bootStrap = new ServerBootstrap();
        private ChannelFuture cf;
        private String zkAddress;
        private String serversPath;
        private String currentServerPath;
        private ServerData sd;
    
        private volatile boolean binded = false;
    
        private final ZkClient zc;
        private final RegistProvider registProvider;
    
        private static final Integer SESSION_TIME_OUT = 10000;
        private static final Integer CONNECT_TIME_OUT = 10000;
    
    
    
        public String getCurrentServerPath() {
            return currentServerPath;
        }
    
        public String getZkAddress() {
            return zkAddress;
        }
    
        public String getServersPath() {
            return serversPath;
        }
    
        public ServerData getSd() {
            return sd;
        }
    
        public void setSd(ServerData sd) {
            this.sd = sd;
        }
    
        public ServerImpl(String zkAddress, String serversPath, ServerData sd){
            this.zkAddress = zkAddress;
            this.serversPath = serversPath;
            this.zc = new ZkClient(this.zkAddress,SESSION_TIME_OUT,CONNECT_TIME_OUT,new SerializableSerializer());
            this.registProvider = new DefaultRegistProvider();
            this.sd = sd;
        }
    
        //初始化服务端
        private void initRunning() throws Exception {
            String mePath = serversPath.concat("/").concat(sd.getPort().toString());
            //注册到zookeeper
            registProvider.regist(new ZooKeeperRegistContext(mePath,zc,sd));
            currentServerPath = mePath;
        }
    
        public void bind() {
    
            if (binded){
                return;
            }
    
            System.out.println(sd.getPort()+":binding...");
    
            try {
                initRunning();
            } catch (Exception e) {
                e.printStackTrace();
                return;
            }
    
            bootStrap.group(bossGroup,workGroup)
                    .channel(NioServerSocketChannel.class)
                    .option(ChannelOption.SO_BACKLOG, 1024)
                    .childHandler(new ChannelInitializer<SocketChannel>() {
                        @Override
                        public void initChannel(SocketChannel ch) throws Exception {
                            ChannelPipeline p = ch.pipeline();
                            p.addLast(new ServerHandler(new DefaultBalanceUpdateProvider(currentServerPath,zc)));
                        }
                    });
    
            try {
                cf =  bootStrap.bind(sd.getPort()).sync();
                binded = true;
                System.out.println(sd.getPort()+":binded...");
                cf.channel().closeFuture().sync();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }finally{
                bossGroup.shutdownGracefully();
                workGroup.shutdownGracefully();
            }
    
        }
    
    }
    package com.test.cbd.zookeeper.loadbalance;
    
    import java.util.ArrayList;
    import java.util.List;
    
    /**
     * 用于测试,负责启动Work Server
     */
    public class ServerRunner {
    
        private static final int  SERVER_QTY = 2;
        private static final String  ZOOKEEPER_SERVER = "192.168.1.105:2181";
        private static final String  SERVERS_PATH = "/servers";
    
        public static void main(String[] args) {
    
            List<Thread> threadList = new ArrayList<Thread>();
    
            for(int i=0; i<SERVER_QTY; i++){
    
                final Integer count = i;
                Thread thread = new Thread(new Runnable() {
    
                    public void run() {
                        ServerData sd = new ServerData();
                        sd.setBalance(0);
                        sd.setHost("127.0.0.1");
                        sd.setPort(6000+count);
                        Server server = new ServerImpl(ZOOKEEPER_SERVER,SERVERS_PATH,sd);
                        server.bind();
                    }
                });
                threadList.add(thread);
                thread.start();
            }
    
            for (int i=0; i<threadList.size(); i++){
                try {
                    threadList.get(i).join();
                } catch (InterruptedException ignore) {
                    //
                }
    
            }
    
    
        }
    
    }
    package com.test.cbd.zookeeper.loadbalance;
    
    import org.I0Itec.zkclient.ZkClient;
    
    public class ZooKeeperRegistContext {
    
        private String path;
        private ZkClient zkClient;
        private Object data;
    
        public ZooKeeperRegistContext(String path, ZkClient zkClient, Object data) {
            super();
            this.path = path;
            this.zkClient = zkClient;
            this.data = data;
        }
        public String getPath() {
            return path;
        }
        public void setPath(String path) {
            this.path = path;
        }
        public ZkClient getZkClient() {
            return zkClient;
        }
        public void setZkClient(ZkClient zkClient) {
            this.zkClient = zkClient;
        }
        public Object getData() {
            return data;
        }
        public void setData(Object data) {
            this.data = data;
        }
    
    }

    客户端代码:

    package com.test.cbd.zookeeper.loadbalance.client;
    
    import java.util.List;
    
    public abstract class AbstractBalanceProvider<T> implements BalanceProvider<T> {
    
        protected abstract T balanceAlgorithm(List<T> items);
        protected abstract List<T> getBalanceItems();
    
        public T getBalanceItem(){
            return balanceAlgorithm(getBalanceItems());
        }
    
    }
    package com.test.cbd.zookeeper.loadbalance.client;
    
    public interface BalanceProvider<T> {
    
        public T getBalanceItem();
    
    }
    package com.test.cbd.zookeeper.loadbalance.client;
    
    public interface Client {
    
        // 连接服务器
        public void connect() throws Exception;
        // 断开服务器
        public void disConnect() throws Exception;
    
    }
    package com.test.cbd.zookeeper.loadbalance.client;
    
    import io.netty.channel.ChannelHandlerAdapter;
    import io.netty.channel.ChannelHandlerContext;
    
    public class ClientHandler extends ChannelHandlerAdapter {
    
        @Override
        public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
            // Close the connection when an exception is raised.
            cause.printStackTrace();
            ctx.close();
        }
    }
    package com.test.cbd.zookeeper.loadbalance.client;
    
    import com.test.cbd.zookeeper.loadbalance.ServerData;
    import io.netty.bootstrap.Bootstrap;
    import io.netty.channel.Channel;
    import io.netty.channel.EventLoopGroup;
    import io.netty.channel.nio.NioEventLoopGroup;
    import io.netty.channel.socket.nio.NioSocketChannel;
    import org.slf4j.Logger;
    import org.slf4j.LoggerFactory;
    import io.netty.channel.*;
    import io.netty.channel.socket.SocketChannel;
    
    public class ClientImpl implements Client {
    
        private final BalanceProvider<ServerData> provider;
        private EventLoopGroup group = null;
        private Channel channel = null;
    
        private final Logger log = LoggerFactory.getLogger(getClass());
    
        public ClientImpl(BalanceProvider<ServerData> provider) {
            this.provider = provider;
        }
    
        public BalanceProvider<ServerData> getProvider() {
            return provider;
        }
    
        public void connect(){
    
            try{
    
                ServerData serverData = provider.getBalanceItem(); // 获取负载最小的服务器信息,并与之建立连接
    
                System.out.println("connecting to "+serverData.getHost()+":"+serverData.getPort()+", it's balance:"+serverData.getBalance());
    
                group = new NioEventLoopGroup();
                Bootstrap b = new Bootstrap();
                b.group(group)
                        .channel(NioSocketChannel.class)
                        .handler(new ChannelInitializer<SocketChannel>() {
                            @Override
                            public void initChannel(SocketChannel ch) throws Exception {
                                ChannelPipeline p = ch.pipeline();
                                p.addLast(new ClientHandler());
                            }
                        });
                ChannelFuture f = b.connect(serverData.getHost(),serverData.getPort()).syncUninterruptibly();
                channel = f.channel();
    
                System.out.println("started success!");
    
            }catch(Exception e){
    
                System.out.println("连接异常:"+e.getMessage());
    
            }
    
        }
    
        public void disConnect(){
    
            try{
    
                if (channel!=null)
                    channel.close().syncUninterruptibly();
    
                group.shutdownGracefully();
                group = null;
    
                log.debug("disconnected!");
    
            }catch(Exception e){
    
                log.error(e.getMessage());
    
            }
        }
    
    }
    package com.test.cbd.zookeeper.loadbalance.client;
    
    import com.test.cbd.zookeeper.loadbalance.ServerData;
    
    import java.io.BufferedReader;
    import java.io.InputStreamReader;
    import java.util.ArrayList;
    import java.util.List;
    
    public class ClientRunner {
    
        private static final int  CLIENT_QTY = 3;
        private static final String  ZOOKEEPER_SERVER = "192.168.1.105:2181";
        private static final String  SERVERS_PATH = "/servers";
    
        public static void main(String[] args) {
    
            List<Thread> threadList = new ArrayList<Thread>(CLIENT_QTY);
            final List<Client> clientList = new ArrayList<Client>();
            final BalanceProvider<ServerData> balanceProvider = new DefaultBalanceProvider(ZOOKEEPER_SERVER, SERVERS_PATH);
    
            try{
    
                for(int i=0; i<CLIENT_QTY; i++){
    
                    Thread thread = new Thread(new Runnable() {
    
                        public void run() {
                            Client client = new ClientImpl(balanceProvider);
                            clientList.add(client);
                            try {
                                client.connect();
                            } catch (Exception e) {
                                e.printStackTrace();
                            }
                        }
                    });
                    threadList.add(thread);
                    thread.start();
                    //延时
                    Thread.sleep(2000);
    
                }
    
                System.out.println("敲回车键退出!
    ");
                new BufferedReader(new InputStreamReader(System.in)).readLine();
    
    
            }catch(Exception e){
    
                e.printStackTrace();
    
            }finally{
                //关闭客户端
                for (int i=0; i<clientList.size(); i++){
                    try {
                        clientList.get(i);
                        clientList.get(i).disConnect();
                    } catch (Exception ignore) {
                        //ignore
                    }
                }
                //关闭线程
                for (int i=0; i<threadList.size(); i++){
                    threadList.get(i).interrupt();
                    try{
                        threadList.get(i).join();
                    }catch (InterruptedException e){
                        //ignore
                    }
                }
            }
        }
    }
    package com.test.cbd.zookeeper.loadbalance.client;
    
    import com.test.cbd.zookeeper.loadbalance.ServerData;
    import org.I0Itec.zkclient.ZkClient;
    import org.I0Itec.zkclient.serialize.SerializableSerializer;
    
    import java.util.ArrayList;
    import java.util.Collections;
    import java.util.List;
    
    public class DefaultBalanceProvider extends AbstractBalanceProvider<ServerData> {
    
        private final String zkServer; // zookeeper服务器地址
        private final String serversPath; // servers节点路径
        private final ZkClient zc;
    
        private static final Integer SESSION_TIME_OUT = 10000;
        private static final Integer CONNECT_TIME_OUT = 10000;
    
        public DefaultBalanceProvider(String zkServer, String serversPath) {
            this.serversPath = serversPath;
            this.zkServer = zkServer;
    
            this.zc = new ZkClient(this.zkServer, SESSION_TIME_OUT, CONNECT_TIME_OUT,
                    new SerializableSerializer());
    
        }
    
        @Override
        protected ServerData balanceAlgorithm(List<ServerData> items) {
            if (items.size()>0){
                Collections.sort(items); // 根据负载由小到大排序
                return items.get(0); // 返回负载最小的那个
            }else{
                return null;
            }
        }
    
        /**
         * 从zookeeper中拿到所有工作服务器的基本信息
         */
        @Override
        protected List<ServerData> getBalanceItems() {
    
            List<ServerData> sdList = new ArrayList<ServerData>();
            List<String> children = zc.getChildren(this.serversPath);
            for(int i=0; i<children.size();i++){
                ServerData sd = zc.readData(serversPath+"/"+children.get(i));
                sdList.add(sd);
            }
            return sdList;
    
        }
    
    }
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  • 原文地址:https://www.cnblogs.com/tinyj/p/10029299.html
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