content: package com.alibaba.otter.canal.client.impl.running;
  
  import java.net.InetSocketAddress;
  import java.text.MessageFormat;
  import java.util.concurrent.Executors;
  import java.util.concurrent.ScheduledExecutorService;
  import java.util.concurrent.TimeUnit;
  
  import org.I0Itec.zkclient.IZkDataListener;
  import org.I0Itec.zkclient.exception.ZkException;
  import org.I0Itec.zkclient.exception.ZkInterruptedException;
  import org.I0Itec.zkclient.exception.ZkNoNodeException;
  import org.I0Itec.zkclient.exception.ZkNodeExistsException;
  import org.apache.zookeeper.CreateMode;
  import org.slf4j.Logger;
  import org.slf4j.LoggerFactory;
  import org.slf4j.MDC;
  
  import com.alibaba.otter.canal.client.impl.ServerNotFoundException;
  import com.alibaba.otter.canal.common.AbstractCanalLifeCycle;
  import com.alibaba.otter.canal.common.utils.BooleanMutex;
  import com.alibaba.otter.canal.common.utils.JsonUtils;
  import com.alibaba.otter.canal.common.zookeeper.ZkClientx;
  import com.alibaba.otter.canal.common.zookeeper.ZookeeperPathUtils;
  import com.alibaba.otter.canal.protocol.exception.CanalClientException;
  
  /**
   * clinet running控制
   * 
   * @author jianghang 2012-11-22 下午03:43:01
   * @version 1.0.0
   */
  public class ClientRunningMonitor extends AbstractCanalLifeCycle {
  
      private static final Logger        logger       = LoggerFactory.getLogger(ClientRunningMonitor.class);
      private ZkClientx                  zkClient;
      private String                     destination;
      private ClientRunningData          clientData;
      private IZkDataListener            dataListener;
      private BooleanMutex               mutex        = new BooleanMutex(false);
      private volatile boolean           release      = false;
      private volatile ClientRunningData activeData;
      private ScheduledExecutorService   delayExector = Executors.newScheduledThreadPool(1);
      private ClientRunningListener      listener;
      private int                        delayTime    = 5;
  
      public ClientRunningMonitor(){
          dataListener = new IZkDataListener() {
  
              public void handleDataChange(String dataPath, Object data) throws Exception {
                  MDC.put("destination", destination);
                  ClientRunningData runningData = JsonUtils.unmarshalFromByte((byte[]) data, ClientRunningData.class);
                  if (!isMine(runningData.getAddress())) {
                      mutex.set(false);
                  }
  
                  if (!runningData.isActive() && isMine(runningData.getAddress())) { // 说明出现了主动释放的操作，并且本机之前是active
                      release = true;
                      releaseRunning();// 彻底释放mainstem
                  }
  
                  activeData = (ClientRunningData) runningData;
              }
  
              public void handleDataDeleted(String dataPath) throws Exception {
                  MDC.put("destination", destination);
                  mutex.set(false);
                  // 触发一下退出,可能是人为干预的释放操作或者网络闪断引起的session expired timeout
                  processActiveExit();
                  if (!release && activeData != null && isMine(activeData.getAddress())) {
                      // 如果上一次active的状态就是本机，则即时触发一下active抢占
                      initRunning();
                  } else {
                      // 否则就是等待delayTime，避免因网络瞬端或者zk异常，导致出现频繁的切换操作
                      delayExector.schedule(() -> initRunning(), delayTime, TimeUnit.SECONDS);
                  }
              }
  
          };
  
      }
  
      public void start() {
          super.start();
  
          String path = ZookeeperPathUtils.getDestinationClientRunning(this.destination, clientData.getClientId());
          zkClient.subscribeDataChanges(path, dataListener);
          initRunning();
      }
  
      public void stop() {
          super.stop();
  
          String path = ZookeeperPathUtils.getDestinationClientRunning(this.destination, clientData.getClientId());
          zkClient.unsubscribeDataChanges(path, dataListener);
          releaseRunning(); // 尝试一下release
          // Fix issue #697
          if (delayExector != null) {
              delayExector.shutdown();
          }
      }
  
      // 改动记录：
      // 1,在方法上加synchronized关键字,保证同步顺序执行;
      // 2,判断Zk上已经存在的activeData是否是本机，是的话把mutex重置为true，否则会导致死锁
      // 3,增加异常处理，保证出现异常时，running节点能被删除,否则会导致死锁
      public synchronized void initRunning() {
          if (!isStart()) {
              return;
          }
  
          String path = ZookeeperPathUtils.getDestinationClientRunning(this.destination, clientData.getClientId());
          // 序列化
          byte[] bytes = JsonUtils.marshalToByte(clientData);
          try {
              mutex.set(false);
              zkClient.create(path, bytes, CreateMode.EPHEMERAL);
              processActiveEnter();// 触发一下事件
              activeData = clientData;
              mutex.set(true);
          } catch (ZkNodeExistsException e) {
              bytes = zkClient.readData(path, true);
              if (bytes == null) {// 如果不存在节点，立即尝试一次
                  initRunning();
              } else {
                  activeData = JsonUtils.unmarshalFromByte(bytes, ClientRunningData.class);
                  // 如果发现已经存在,判断一下是否自己,避免活锁
                  if (activeData.getAddress().contains(":") && isMine(activeData.getAddress())) {
                      mutex.set(true);
                  }
              }
          } catch (ZkNoNodeException e) {
              zkClient.createPersistent(ZookeeperPathUtils.getClientIdNodePath(this.destination, clientData.getClientId()),
                  true); // 尝试创建父节点
              initRunning();
          } catch (Throwable t) {
              logger.error(MessageFormat.format("There is an error when execute initRunning method, with destination [{0}].",
                  destination),
                  t);
  
              // fixed issue 1220, 针对server节点不工作避免死循环
              if (t instanceof ServerNotFoundException) {
                  try {
                      Thread.sleep(1000);
                  } catch (InterruptedException e) {
                  }
              }
  
              // 出现任何异常尝试release
              releaseRunning();
              throw new CanalClientException("something goes wrong in initRunning method. ", t);
          }
      }
  
      /**
       * 阻塞等待自己成为active，如果自己成为active，立马返回
       * 
       * @throws InterruptedException
       */
      public void waitForActive() throws InterruptedException {
          initRunning();
          mutex.get();
      }
  
      /**
       * 检查当前的状态
       */
      public boolean check() {
          String path = ZookeeperPathUtils.getDestinationClientRunning(this.destination, clientData.getClientId());
          try {
              byte[] bytes = zkClient.readData(path);
              ClientRunningData eventData = JsonUtils.unmarshalFromByte(bytes, ClientRunningData.class);
              activeData = eventData;// 更新下为最新值
              // 检查下nid是否为自己
              boolean result = isMine(activeData.getAddress());
              if (!result) {
                  logger.warn("canal is running in [{}] , but not in [{}]",
                      activeData.getAddress(),
                      clientData.getAddress());
              }
              return result;
          } catch (ZkNoNodeException e) {
              logger.warn("canal is not run any in node");
              return false;
          } catch (ZkInterruptedException e) {
              logger.warn("canal check is interrupt");
              Thread.interrupted();// 清除interrupt标记
              return check();
          } catch (ZkException e) {
              logger.warn("canal check is failed");
              return false;
          }
      }
  
      public boolean releaseRunning() {
          if (check()) {
              String path = ZookeeperPathUtils.getDestinationClientRunning(this.destination, clientData.getClientId());
              zkClient.delete(path);
              mutex.set(false);
              processActiveExit();
              return true;
          }
  
          return false;
      }
  
      // ====================== helper method ======================
  
      private boolean isMine(String address) {
          return address.equals(clientData.getAddress());
      }
  
      private void processActiveEnter() {
          if (listener != null) {
              // 触发回调，建立与server的socket链接
              InetSocketAddress connectAddress = listener.processActiveEnter();
              String address = connectAddress.getAddress().getHostAddress() + ":" + connectAddress.getPort();
              this.clientData.setAddress(address);
  
              String path = ZookeeperPathUtils.getDestinationClientRunning(this.destination,
                  this.clientData.getClientId());
              // 序列化
              byte[] bytes = JsonUtils.marshalToByte(clientData);
              zkClient.writeData(path, bytes);
          }
      }
  
      private void processActiveExit() {
          if (listener != null) {
              listener.processActiveExit();
          }
      }
  
      public void setListener(ClientRunningListener listener) {
          this.listener = listener;
      }
  
      // ===================== setter / getter =======================
  
      public void setDestination(String destination) {
          this.destination = destination;
      }
  
      public void setClientData(ClientRunningData clientData) {
          this.clientData = clientData;
      }
  
      public void setDelayTime(int delayTime) {
          this.delayTime = delayTime;
      }
  
      public void setZkClient(ZkClientx zkClient) {
          this.zkClient = zkClient;
      }
  
  }
  