zookeeper系列（四）實戰負載均衡

zookeeper系列（一）zookeeper必知
zookeeper系列（二）實戰master選舉
zookeeper系列（三）實戰數據發佈訂閱
zookeeper系列（四）實戰負載均衡
zookeeper系列（五）實戰分佈式鎖
zookeeper系列（六）實戰分佈式隊列
zookeeper系列（七）實戰分佈式命名服務
zookeeper系列（八）zookeeper運維

負載均衡

負載均衡是一種手段，用來把對某種資源的訪問分攤給不一樣的設備，從而減輕單點的壓力。

架構圖

圖中左側爲ZooKeeper集羣，右側上方爲工做服務器，下面爲客戶端。每臺工做服務器在啓動時都會去zookeeper的servers節點下注冊臨時節點，每臺客戶端在啓動時都會去servers節點下取得全部可用的工做服務器列表，並經過必定的負載均衡算法計算得出一臺工做服務器，並與之創建網絡鏈接。網絡鏈接咱們採用開源框架netty。

流程圖

負載均衡客戶端流程

服務端主體流程

類圖

Server端核心類

每一個服務端對應一個Server接口，ServiceImpl是服務端的實現類。把服務端啓動時的註冊過程抽出爲一個接口RegistProvider，並給予一個默認實現DefaultRegistProvider，它將用到一個上下文的類ZooKeeperRegistContext。咱們的服務端是給予Netty的，它須要ServerHandler來處理與客戶端之間的鏈接，當有客戶端創建或失去鏈接時，咱們都須要去修改當前服務器的負載信息，咱們把修改負載信息的過程也抽出爲一個接口BalanceUpdateProvider，而且給予了一個默認實現DefaultBalanceUpdateProvider。ServerRunner是調度類，負責調度咱們的Server。

Client端核心類

每一個客戶端都須要實現一個Client接口，ClientImpl是實現，Client須要ClientHandler來處理與服務器以前的通信，同時它須要BalanceProvider爲它提供負載均衡的算法。BalanceProvider是接口，它有2個實現類，一個是抽象的實現AbstractBalanceProvider，一個是默認的實現DefaultBalanceProvider。ServerData是服務端和客戶端共用的一個類，服務端會把本身的基本信息，包括負載信息，打包成ServerData並寫入到zookeeper中，客戶端在計算負載的時候須要到zookeeper中拿到ServerData，並取得服務端的地址和負載信息。ClientRunner是客戶端的調度類，負責啓動客戶端。

代碼實現

先是Server端的代碼：

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());
    }
    
}

public interface Server {
    
    public void bind();

}

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;
    }    
    
    //初始化服務端
    private void initRunning() throws Exception {
        String mePath = serversPath.concat("/").concat(sd.getPort().toString());
        //註冊到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();
        }
        
    }

}

public interface RegistProvider {
    
    public void regist(Object context) throws Exception;
    
    public void unRegist(Object context) throws Exception;

}

public class DefaultRegistProvider implements RegistProvider {

    // 在zookeeper中建立臨時節點並寫入信息
    public void regist(Object context) throws Exception {

        // Server在zookeeper中註冊本身，須要在zookeeper的目標節點上建立臨時節點並寫入本身
        // 將須要的如下3個信息包裝成上下文傳入
        // 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;
    }

}

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;
    }

}

/**
 * 處理服務端與客戶端之間的通訊
 */
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;
    }    

    // 創建鏈接時增長負載
    @Override
    public void channelActive(ChannelHandlerContext ctx) throws Exception {
        System.out.println("one client connect...");
        balanceUpdater.addBalance(BALANCE_STEP);
    }

    // 斷開鏈接時減小負載
    @Override
    public void channelInactive(ChannelHandlerContext ctx) throws Exception {
        balanceUpdater.reduceBalance(BALANCE_STEP);
    }

    @Override
    public void exceptionCaught(ChannelHandlerContext ctx, Throwable cause) {
        cause.printStackTrace();
        ctx.close();
    }


}

public interface BalanceUpdateProvider {

    // 增長負載
    public boolean addBalance(Integer step);

    // 減小負載
    public boolean reduceBalance(Integer step);

}

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;

        // 增長負載：讀取服務器的信息ServerData，增長負載，並寫回zookeeper
        while (true) {
            try {
                sd = zc.readData(this.serverPath, stat);
                sd.setBalance(sd.getBalance() + step);
                // 帶上版本，由於可能有其餘客戶端鏈接到服務器修改了負載
                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;
            }
        }
    }

}

/**
 * 用於測試,負責啓動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) {
                //
            }
            
        }
        

    }

}

再看Client端的代碼：

public interface Client {

    // 鏈接服務器
    public void connect() throws Exception;
    // 斷開服務器
    public void disConnect() throws Exception;
    
}

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(); // 獲取負載最小的服務器信息，並與之創建鏈接
            
            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("鏈接異常:"+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());
            
        }
    }

}

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();
    }
}

public interface BalanceProvider<T> {
    
    public T getBalanceItem();

}

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());
    }

}

public class DefaultBalanceProvider extends AbstractBalanceProvider<ServerData> {

    private final String zkServer; // zookeeper服務器地址
    private final String serversPath; // servers節點路徑
    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); // 根據負載由小到大排序
            return items.get(0); // 返回負載最小的那個
        }else{
            return null;
        }
    }

    /**
     * 從zookeeper中拿到全部工做服務器的基本信息
     */
    @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;
        
    }

}

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();
                    //延時
                    Thread.sleep(2000);
                    
                }
                
                System.out.println("敲回車鍵退出！\n");
                new BufferedReader(new InputStreamReader(System.in)).readLine();
                
                
            }catch(Exception e){
                
                e.printStackTrace();
            
            }finally{
                //關閉客戶端
                for (int i=0; i<clientList.size(); i++){
                    try {
                        clientList.get(i);
                        clientList.get(i).disConnect();
                    } catch (Exception ignore) {
                        //ignore
                    }                    
                }
                //關閉線程
                for (int i=0; i<threadList.size(); i++){
                    threadList.get(i).interrupt();
                    try{
                        threadList.get(i).join();
                    }catch (InterruptedException e){
                        //ignore
                    }                                
                }                                
            }            
        }
}

咱們先啓動服務端ServerRunner

6000:binding...
6000:binded...
6001:binding...
6001:binded...

再來啓動客戶端ClientRunner

connecting to 127.0.0.1:6000, it's balance 0
started success!
connecting to 127.0.0.1:6001, it's balance 0
started success!
connecting to 127.0.0.1:6000, it's balance 1
started success!
敲回車退出!

zookeeper系列（一）zookeeper必知
zookeeper系列（二）實戰master選舉
zookeeper系列（三）實戰數據發佈訂閱
zookeeper系列（四）實戰負載均衡
zookeeper系列（五）實戰分佈式鎖
zookeeper系列（六）實戰分佈式隊列
zookeeper系列（七）實戰分佈式命名服務
zookeeper系列（八）zookeeper運維