基于zookeeper的MySQL主主负载均衡的简单实现

1.先上原理图

2.说明

两个mysql采用主主同步的方式进行部署。

在安装mysql的服务器上安装客户端（目前是这么做，以后想在zookeeper扩展集成），客户端实时监控mysql应用的可用性，可用时想zookeepercreateNode，当网络不可用或者mysql应用不可用时，建立的znode消失。

在客户端，通过改造proxool数据库连接池的方式，在建立连接之前，从zookeeper中去取真实的数据库URL，如果有多个URL，即有多个服务时，采用随机算法去拿连接（以后准备扩展权重）。当连接不可用时，数据库连接池将重建连接，这时候又回去zookeeper拿连接，因为agent建立的临时znode消失了，就不能拿到已经失效的url了。

这个方案只是初步的实验和实现了，还有很多后续的问题，主要为了解决lvs+keepalived只能在同一个区域内的问题。

3.部分实现

1).agent

/** * 数据库可用性检测 * @author tomsnail * @date 2015年4月3日 上午10:11:51 */public class TestMySQL {  public static boolean test(String url){     Connection conn = null;     Statement stmt = null;     ResultSet rs  = null;     String sql = ConfigHelp.getLocalConifg("jdbc_inventory.house-keeping-test-sql", "select 0");      try {        Class.forName(ConfigHelp.getLocalConifg("jdbc_inventory.driver-class", "com.mysql.jdbc.Driver"));// 动态加载mysql驱动        conn = DriverManager.getConnection(url);        stmt = conn.createStatement();        rs = stmt.executeQuery(sql);        while (rs.next()) {        }        return true;      } catch (SQLException e) {        e.printStackTrace();      } catch (Exception e) {        e.printStackTrace();      } finally {        try {          if(rs!=null){            rs.close();          }          if(stmt!=null){            stmt.close();          }          if(conn!=null)            conn.close();        } catch (SQLException e) {          e.printStackTrace();        }      }    return false;  }}

/** * zookeeper客户端 * @author tomsnail * @date 2015年4月3日 上午10:11:51 */public class TestServer {  private static final Logger logger = LoggerFactory      .getLogger(TestServer.class);  private static ZooKeeper zk;  private String path;  //同步锁  private Lock _lock = new ReentrantLock();  // 用于等待 SyncConnected 事件触发后继续执行当前线程  private CountDownLatch latch = new CountDownLatch(1);  public TestServer() {    zk = connectServer();    new Thread(new Runnable() {      @Override      public void run() {        while (true) {          try {            Thread.currentThread().sleep(3000);          } catch (InterruptedException e) {            e.printStackTrace();          }          //logger.info("check zk...");          _lock.lock();          if (zk != null) {            if (zk.getState().isAlive()                && zk.getState().isConnected()) {              //logger.info("zk is ok");              _lock.unlock();              continue;            }          }          close();          logger.info("reConnectServer ...");          zk = connectServer();          logger.info("reConnectServer ok");          _lock.unlock();        }      }      private void close() {        if(zk!=null){          try {            zk.close();          } catch (InterruptedException e) {            e.printStackTrace();          }          zk = null;        }      }    }).start();  }  // 连接 ZooKeeper 服务器  private ZooKeeper connectServer() {    ZooKeeper zk = null;    try {      zk = new ZooKeeper(ConfigHelp.ZK_CONNECTION_STRING,          ConfigHelp.ZK_SESSION_TIMEOUT, new Watcher() {            @Override            public void process(WatchedEvent event) {              if (event.getState() == Event.KeeperState.SyncConnected) {                latch.countDown(); // 唤醒当前正在执行的线程              }            }          });      latch.await(); // 使当前线程处于等待状态    } catch (Exception e) {      logger.error("", e);    }    if (zk != null) {      try {        Stat stat = zk.exists(ConfigHelp.ZK_ROOT_PATH, false);        if (stat == null) {          String path = zk.create(ConfigHelp.ZK_ROOT_PATH,              "".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE,              CreateMode.PERSISTENT); // 创建一个临时性且有序的 ZNode          logger.info("create zookeeper node ({})", path);        }        stat = zk.exists(ConfigHelp.ZK_RMI_PATH, false);        if (stat == null) {          String path = zk.create(ConfigHelp.ZK_RMI_PATH,              "".getBytes(), ZooDefs.Ids.OPEN_ACL_UNSAFE,              CreateMode.PERSISTENT); // 创建一个临时性且有序的 ZNode          logger.info("create zookeeper node ({})", path);        }      } catch (Exception e) {        e.printStackTrace();      }    }    return zk;  }  // 创建 ZNode  public void createNode(String url) {    _lock.lock();    try {      byte[] data = url.getBytes();      path = zk.create(ConfigHelp.ZK_RMI_PATH + "/", data,          ZooDefs.Ids.OPEN_ACL_UNSAFE,          CreateMode.EPHEMERAL_SEQUENTIAL); // 创建一个临时性且有序的 ZNode      logger.info("create zookeeper node ({} => {})", path, url);    } catch (Exception e) {      logger.error("", e);      e.printStackTrace();    }    _lock.unlock();  }  public void deleteNode(String url){    _lock.lock();    try {      Stat stat = zk.exists(path, false);      if(stat!=null){        zk.delete(url, stat.getVersion());      }    } catch (Exception e) {      e.printStackTrace();    }    _lock.unlock();  }}

/** * 数据库检测测试主类 * @author tomsnail * @date 2015年4月3日 上午10:11:51 */public class TestMain {  private static TestServer testServer = new TestServer();  public static void main(String[] args) {    String url = ConfigHelp.getLocalConifg("jdbc_inventory.driver-url", "select 0");    boolean isOK = false;    while(true){      if(TestMySQL.test(url)){        if(isOK){        }else{          testServer.createNode(url);//建立znode        }        isOK = true;      }else{        isOK = false;        testServer.deleteNode(url);//删除znode      }      try {        Thread.currentThread().sleep(2000);      } catch (InterruptedException e) {        e.printStackTrace();      }    }  }}

2).proxool

/** * zookeeper信息定义类 * @author tomsnail * @date 2015年4月2日 下午6:49:13 */public class ZkInfoDefinition {  public static final String PREFIX_ZK = "zookeeper";  public static final String ZK_URL = "zkUrl";  public static final String ZK_SESSION_TIMEOUT = "sessionTimeout";  public static final String ZK_PATH = "zkPath";  public static final String ZK_ENABLE = "zkEnable";  public static String zkUrl="192.168.102.1:31315";  public static int sessionTimeout = 5000;  public static boolean isEnable = false;  public static String zkPath = "/root/db";  public String getZkUrl() {    return zkUrl;  }  public void setZkUrl(String zkUrl) {    this.zkUrl = zkUrl;  }  public int getSessionTimeout() {    return sessionTimeout;  }  public void setSessionTimeout(int sessionTimeout) {    this.sessionTimeout = sessionTimeout;  }  public String getZkPath() {    return zkPath;  }  public void setZkPath(String zkPath) {    this.zkPath = zkPath;  }  public ZkInfoDefinition(String zkUrl, int sessionTimeout, String zkPath) {    super();    this.zkUrl = zkUrl;    this.sessionTimeout = sessionTimeout;    this.zkPath = zkPath;  }  public ZkInfoDefinition(){  }}

/** * zookeeper客户端 * @author tomsnail * @date 2015年4月3日 上午10:15:11 */public class ZkClient {     private static final Logger logger = LoggerFactory.getLogger(ZkClient.class);    // 用于等待 SyncConnected 事件触发后继续执行当前线程    private CountDownLatch latch = new CountDownLatch(1);    // 定义一个 volatile 成员变量，用于保存最新的 RMI 地址（考虑到该变量或许会被其它线程所修改，一旦修改后，该变量的值会影响到所有线程）    private volatile List<String> dataList = new ArrayList<String>();    private Lock _lock = new ReentrantLock();    private static  ZooKeeper zk;    private LBUrl lbUrl;    public ZkClient(){      this(new BasicLBUrl());    }    // 构造器    public ZkClient(LBUrl lbUrl) {      this.lbUrl = lbUrl;      zk = connectServer(); // 连接 ZooKeeper 服务器并获取 ZooKeeper 对象      watchNode();      new Thread(new Runnable() {        @Override        public void run() {          while (true) {            try {              Thread.currentThread().sleep(3000);            } catch (InterruptedException e) {              e.printStackTrace();            }            _lock.lock();            if (zk != null) {              if (zk.getState().isAlive()                  && zk.getState().isConnected()) {                _lock.unlock();                continue;              }            }            if(zk!=null){              try {                zk.close();              } catch (InterruptedException e) {                e.printStackTrace();              }              zk = null;            }            zk = connectServer();            _lock.unlock();          }        }      }).start();    }    // 查找 URL 服务    public String getUrl() {      if (dataList!=null&&dataList.size()>0) {         return this.lbUrl.getUrl(dataList);      }      return null;    }    public List<String> getUrls(){      return dataList;    }    // 连接 ZooKeeper 服务器    private ZooKeeper connectServer() {      ZooKeeper zk = null;      try {        zk = new ZooKeeper(ZkInfoDefinition.zkUrl, ZkInfoDefinition.sessionTimeout, new Watcher() {          @Override          public void process(WatchedEvent event) {            if (event.getState() == Event.KeeperState.SyncConnected) {              latch.countDown(); // 唤醒当前正在执行的线程            }          }        });        latch.await(); // 使当前线程处于等待状态      } catch (Exception e) {        logger.error("", e);      }      return zk;    }    // 观察 /registry 节点下所有子节点是否有变化    private void watchNode() {      _lock.lock();      if(zk!=null&&zk.getState().isAlive()&&zk.getState().isConnected()){      }else{        if(zk!=null){          try {            zk.close();          } catch (InterruptedException e) {            e.printStackTrace();          }          zk = null;        }        zk = connectServer();      }      try {        List<String> nodeList = zk.getChildren(ZkInfoDefinition.zkPath, new Watcher() {          @Override          public void process(WatchedEvent event) {            if (event.getType() == Event.EventType.NodeChildrenChanged) {              watchNode(); // 若子节点有变化，则重新调用该方法（为了获取最新子节点中的数据）            }          }        });        List<String> dataList = new ArrayList<String>(); // 用于存放 /registry 所有子节点中的数据        for (String node : nodeList) {          byte[] data = zk.getData(ZkInfoDefinition.zkPath + "/" + node, false, null); // 获取 /registry 的子节点中的数据          dataList.add(new String(data));        }        logger.debug("node data: {}", dataList);        this.dataList = dataList;      } catch (Exception e) {        logger.error("", e);      }      _lock.unlock();    }    public static void main(String[] args) {      ZkClient client = new ZkClient();      System.out.println(client.getUrl());    }}

View Code

/** * 从zookeeper获得URL连接操作类 * @author tomsnail * @date 2015年4月2日 下午6:56:06 */public class ZkUrlOperation {  private static final ZkUrlOperation instance = new ZkUrlOperation();  private static ZkInfoDefinition zkInfoDefinition;  private static ZkClient zkClient;  private static final byte[] _lock = new byte[0];  private  ZkUrlOperation(){  }  public static ZkUrlOperation getInstance(){    return instance;  }  public  void addZkInfoDefinition(ZkInfoDefinition zkInfoDefinition){    ZkUrlOperation.zkInfoDefinition = zkInfoDefinition;  }  public  void addZkInfoDefinition(String key,String value){    if(ZkUrlOperation.zkInfoDefinition==null){      ZkUrlOperation.zkInfoDefinition = new ZkInfoDefinition();    }    if(key.contains(ZkInfoDefinition.ZK_PATH)){      ZkUrlOperation.zkInfoDefinition.setZkPath(value);    }    if(key.contains(ZkInfoDefinition.ZK_SESSION_TIMEOUT)){      ZkUrlOperation.zkInfoDefinition.setSessionTimeout(Integer.valueOf(value));;    }    if(key.contains(ZkInfoDefinition.ZK_URL)){      ZkUrlOperation.zkInfoDefinition.setZkUrl(value);;    }    if(key.contains(ZkInfoDefinition.ZK_ENABLE)){      ZkUrlOperation.zkInfoDefinition.isEnable = Boolean.valueOf(value);    }  }  public String getUrl(){    synchronized (_lock) {      if(zkInfoDefinition.isEnable){        if(zkClient==null){          zkClient = new ZkClient();        }        String url = zkClient.getUrl();        return url;      }else{        return "";      }    }  }  public boolean isAvailUrl(String url){    synchronized (_lock) {      if(zkInfoDefinition.isEnable){        if(zkClient==null){          zkClient = new ZkClient();        }        List<String> urls = zkClient.getUrls();        for(int i=0;i<urls.size();i++){          if(url.equals(urls.get(i))){            return true;          }        }        return false;      }      return false;    }  }}