content: /**
   *
   * Licensed to the Apache Software Foundation (ASF) under one
   * or more contributor license agreements.  See the NOTICE file
   * distributed with this work for additional information
   * regarding copyright ownership.  The ASF licenses this file
   * to you under the Apache License, Version 2.0 (the
   * "License"); you may not use this file except in compliance
   * with the License.  You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  package com.alibaba.wasp.zookeeper;
  
  import com.alibaba.wasp.FConstants;
  import com.alibaba.wasp.ZooKeeperConnectionException;
  import org.apache.commons.logging.Log;
  import org.apache.commons.logging.LogFactory;
  import org.apache.hadoop.conf.Configuration;
  import org.apache.hadoop.hbase.Abortable;
  import org.apache.hadoop.hbase.util.Threads;
  import org.apache.zookeeper.KeeperException;
  import org.apache.zookeeper.WatchedEvent;
  import org.apache.zookeeper.Watcher;
  import org.apache.zookeeper.ZooDefs;
  import org.apache.zookeeper.data.ACL;
  
  import java.io.Closeable;
  import java.io.IOException;
  import java.util.ArrayList;
  import java.util.List;
  import java.util.concurrent.CopyOnWriteArrayList;
  import java.util.concurrent.CountDownLatch;
  
  /**
   * Acts as the single ZooKeeper Watcher. One instance of this is instantiated
   * for each Master, FServer, and client process.
   * 
   * <p>
   * This is the only class that implements {@link org.apache.zookeeper.Watcher}. Other internal
   * classes which need to be notified of ZooKeeper events must register with the
   * local instance of this watcher via {@link #registerListener}.
   *
   * <p>
   * This class also holds and manages the connection to ZooKeeper. Code to deal
   * with connection related events and exceptions are handled here.
   */
  public class ZooKeeperWatcher implements Watcher, Abortable, Closeable {
    private static final Log LOG = LogFactory.getLog(ZooKeeperWatcher.class);
  
    // Identifier for this watcher (for logging only). It is made of the prefix
    // passed on construction and the zookeeper sessionid.
    private String identifier;
  
    // zookeeper quorum
    private String quorum;
  
    // zookeeper connection
    private RecoverableZooKeeper recoverableZooKeeper;
  
    // abortable in case of zk failure
    protected Abortable abortable;
  
    // listeners to be notified
    private final List<ZooKeeperListener> listeners = new CopyOnWriteArrayList<ZooKeeperListener>();
  
    // Used by ZKUtil:waitForZKConnectionIfAuthenticating to wait for SASL
    // negotiation to complete
    public CountDownLatch saslLatch = new CountDownLatch(1);
  
    // node names
  
    // base znode for this cluster
    public String baseZNode;
    // znode containing ephemeral nodes of the fservers
    public String fsZNode;
    // znode containing ephemeral nodes of the draining fservers
    public String drainingZNode;
    // znode of currently active master
    private String masterAddressZNode;
    // znode of this master in backup master directory, if not the active master
    public String backupMasterAddressesZNode;
    // znode containing the current cluster state
    public String clusterStateZNode;
    // znode used for entityGroup transitioning and assignment
    public String assignmentZNode;
    // znode used for table disabling/enabling
    public String tableZNode;
    // znode containing the unique cluster ID
    public String clusterIdZNode;
    // znode containing the state of the load balancer
    public String balancerZNode;
  
    // Certain ZooKeeper nodes need to be world-readable
    public static final ArrayList<ACL> CREATOR_ALL_AND_WORLD_READABLE = new ArrayList<ACL>() {
      {
        add(new ACL(ZooDefs.Perms.READ, ZooDefs.Ids.ANYONE_ID_UNSAFE));
        add(new ACL(ZooDefs.Perms.ALL, ZooDefs.Ids.AUTH_IDS));
      }
    };
  
    private final Configuration conf;
  
    private final Exception constructorCaller;
  
    /**
     * Instantiate a ZooKeeper connection and watcher.
     * @param descriptor Descriptive string that is added to zookeeper sessionid
     *          and used as identifier for this instance.
     * @throws java.io.IOException
     * @throws com.alibaba.wasp.ZooKeeperConnectionException
     */
    public ZooKeeperWatcher(Configuration conf, String descriptor,
        Abortable abortable) throws ZooKeeperConnectionException, IOException {
      this(conf, descriptor, abortable, false);
    }
  
    /**
     * Instantiate a ZooKeeper connection and watcher.
     * @param descriptor Descriptive string that is added to zookeeper sessionid
     *          and used as identifier for this instance.
     * @throws java.io.IOException
     * @throws com.alibaba.wasp.ZooKeeperConnectionException
     */
    public ZooKeeperWatcher(Configuration conf, String descriptor,
        Abortable abortable, boolean canCreateBaseZNode) throws IOException,
        ZooKeeperConnectionException {
      this.conf = conf;
      // Capture a stack trace now. Will print it out later if problem so we can
      // distingush amongst the myriad ZKWs.
      try {
        throw new Exception("ZKW CONSTRUCTOR STACK TRACE FOR DEBUGGING");
      } catch (Exception e) {
        this.constructorCaller = e;
      }
      this.quorum = ZKConfig.getZKQuorumServersString(conf);
      // Identifier will get the session id appended later below down when we
      // handle the sync connect event.
      this.identifier = descriptor;
      this.abortable = abortable;
      setNodeNames(conf);
      this.recoverableZooKeeper = ZKUtil.connect(conf, quorum, this, descriptor);
      if (canCreateBaseZNode) {
        createBaseZNodes();
      }
    }
  
    private void createBaseZNodes() throws ZooKeeperConnectionException {
      try {
        // Create all the necessary "directories" of znodes
        ZKUtil.createAndFailSilent(this, baseZNode);
        ZKUtil.createAndFailSilent(this, assignmentZNode);
        ZKUtil.createAndFailSilent(this, fsZNode);
        ZKUtil.createAndFailSilent(this, drainingZNode);
        ZKUtil.createAndFailSilent(this, tableZNode);
        ZKUtil.createAndFailSilent(this, backupMasterAddressesZNode);
      } catch (KeeperException e) {
        throw new ZooKeeperConnectionException(
            prefix("Unexpected KeeperException creating base node"), e);
      }
    }
  
    @Override
    public String toString() {
      return this.identifier;
    }
  
    /**
     * Adds this instance's identifier as a prefix to the passed <code>str</code>
     * @param str String to amend.
     * @return A new string with this instance's identifier as prefix: e.g. if
     *         passed 'hello world', the returned string could be
     */
    public String prefix(final String str) {
      return this.toString() + " " + str;
    }
  
    /**
     * Set the local variable node names using the specified configuration.
     */
    private void setNodeNames(Configuration conf) {
      baseZNode = conf.get(FConstants.ZOOKEEPER_ZNODE_PARENT,
          FConstants.DEFAULT_ZOOKEEPER_ZNODE_PARENT);
      fsZNode = ZKUtil.joinZNode(baseZNode, conf.get("zookeeper.znode.fs", "fs"));
      drainingZNode = ZKUtil.joinZNode(baseZNode,
          conf.get("zookeeper.znode.draining.fs", "draining"));
      masterAddressZNode = ZKUtil.joinZNode(baseZNode,
          conf.get("zookeeper.znode.master", "master"));
      backupMasterAddressesZNode = ZKUtil.joinZNode(baseZNode,
          conf.get("zookeeper.znode.backup.masters", "backup-masters"));
      clusterStateZNode = ZKUtil.joinZNode(baseZNode,
          conf.get("zookeeper.znode.state", "shutdown"));
      assignmentZNode = ZKUtil.joinZNode(baseZNode,
          conf.get("zookeeper.znode.unassigned", "unassigned"));
      tableZNode = ZKUtil.joinZNode(baseZNode,
          conf.get("zookeeper.znode.tableEnableDisable", "table"));
      clusterIdZNode = ZKUtil.joinZNode(baseZNode,
          conf.get("zookeeper.znode.clusterId", "waspid"));
      balancerZNode = ZKUtil.joinZNode(baseZNode,
          conf.get("zookeeper.znode.balancer", "balancer"));
    }
  
    /**
     * Register the specified listener to receive ZooKeeper events.
     * @param listener
     */
    public void registerListener(ZooKeeperListener listener) {
      listeners.add(listener);
    }
  
    /**
     * Register the specified listener to receive ZooKeeper events and add it as
     * the first in the list of current listeners.
     * @param listener
     */
    public void registerListenerFirst(ZooKeeperListener listener) {
      listeners.add(0, listener);
    }
  
    /**
     * Get the connection to ZooKeeper.
     * @return connection reference to zookeeper
     */
    public RecoverableZooKeeper getRecoverableZooKeeper() {
      return recoverableZooKeeper;
    }
  
    public void reconnectAfterExpiration() throws IOException,
        InterruptedException {
      recoverableZooKeeper.reconnectAfterExpiration();
    }
  
    /**
     * Get the quorum address of this instance.
     * @return quorum string of this zookeeper connection instance
     */
    public String getQuorum() {
      return quorum;
    }
  
    /**
     * Method called from ZooKeeper for events and connection status.
     * <p>
     * Valid events are passed along to listeners. Connection status changes are
     * dealt with locally.
     */
    @Override
    public void process(WatchedEvent event) {
      LOG.debug(prefix("Received ZooKeeper Event, " + "type=" + event.getType()
          + ", " + "state=" + event.getState() + ", " + "path=" + event.getPath()));
  
      switch (event.getType()) {
  
        // If event type is NONE, this is a connection status change
        case None: {
          connectionEvent(event);
          break;
        }
  
          // Otherwise pass along to the listeners
  
        case NodeCreated: {
          for (ZooKeeperListener listener : listeners) {
            listener.nodeCreated(event.getPath());
          }
          break;
        }
  
        case NodeDeleted: {
          for (ZooKeeperListener listener : listeners) {
            listener.nodeDeleted(event.getPath());
          }
          break;
        }
  
        case NodeDataChanged: {
          for (ZooKeeperListener listener : listeners) {
            listener.nodeDataChanged(event.getPath());
          }
          break;
        }
  
        case NodeChildrenChanged: {
          for (ZooKeeperListener listener : listeners) {
            listener.nodeChildrenChanged(event.getPath());
          }
          break;
        }
      }
    }
  
    // Connection management
  
    /**
     * Called when there is a connection-related event via the Watcher callback.
     * <p>
     * If Disconnected or Expired, this should shutdown the cluster. But, since we
     * send a KeeperException.SessionExpiredException along with the abort call,
     * it's possible for the Abortable to catch it and try to create a new session
     * with ZooKeeper. This is what the client does in HCM.
     * <p>
     * @param event
     */
    private void connectionEvent(WatchedEvent event) {
      switch (event.getState()) {
        case SyncConnected:
          // Now, this callback can be invoked before the this.zookeeper is set.
          // Wait a little while.
          long finished = System.currentTimeMillis()
              + this.conf.getLong("hbase.zookeeper.watcher.sync.connected.wait",
                  2000);
          while (System.currentTimeMillis() < finished) {
            Threads.sleep(1);
            if (this.recoverableZooKeeper != null)
              break;
          }
          if (this.recoverableZooKeeper == null) {
            LOG.error("ZK is null on connection event -- see stack trace "
                + "for the stack trace when constructor was called on this zkw",
                this.constructorCaller);
            throw new NullPointerException("ZK is null");
          }
          this.identifier = this.identifier + "-0x"
              + Long.toHexString(this.recoverableZooKeeper.getSessionId());
          // Update our identifier. Otherwise ignore.
          LOG.debug(this.identifier + " connected");
          break;
  
        case AuthFailed:
          if (ZKUtil.isSecureZooKeeper(this.conf)) {
            // We could not be authenticated, but clients should proceed anyway.
            // Only access to znodes that require SASL authentication will be
            // denied. The client may never need to access them.
            saslLatch.countDown();
          }
          break;
  
        // Abort the server if Disconnected or Expired
        case Disconnected:
          LOG.debug(prefix("Received Disconnected from ZooKeeper, ignoring"));
          break;
  
        case Expired:
          if (ZKUtil.isSecureZooKeeper(this.conf)) {
            // We consider Expired equivalent to AuthFailed for this
            // connection. Authentication is never going to complete. The
            // client should proceed to do cleanup.
            saslLatch.countDown();
          }
          String msg = prefix(this.identifier + " received expired from "
              + "ZooKeeper, aborting");
          // TODO: One thought is to add call to ZooKeeperListener so say,
          // ZooKeeperNodeTracker can zero out its data values.
          if (this.abortable != null)
            this.abortable.abort(msg,
                new KeeperException.SessionExpiredException());
          break;
  
        default:
          throw new IllegalStateException("Received event is not valid.");
      }
    }
  
    /**
     * Forces a synchronization of this ZooKeeper client connection.
     * <p>
     * Executing this method before running other methods will ensure that the
     * subsequent operations are up-to-date and consistent as of the time that the
     * sync is complete.
     * <p>
     * This is used for compareAndSwap type operations where we need to read the
     * data of an existing node and delete or transition that node, utilizing the
     * previously read version and data. We want to ensure that the version read
     * is up-to-date from when we begin the operation.
     */
    public void sync(String path) {
      this.recoverableZooKeeper.sync(path, null, null);
    }
  
    /**
     * Handles KeeperExceptions in client calls.
     * <p>
     * This may be temporary but for now this gives one place to deal with these.
     * <p>
     * TODO: Currently this method rethrows the exception to let the caller handle
     * <p>
     * @param ke
     * @throws org.apache.zookeeper.KeeperException
     */
    public void keeperException(KeeperException ke) throws KeeperException {
      LOG.error(
          prefix("Received unexpected KeeperException, re-throwing exception"),
          ke);
      throw ke;
    }
  
    /**
     * Handles InterruptedExceptions in client calls.
     * <p>
     * This may be temporary but for now this gives one place to deal with these.
     * <p>
     * TODO: Currently, this method does nothing. Is this ever expected to happen?
     * Do we abort or can we let it run? Maybe this should be logged as WARN? It
     * shouldn't happen?
     * <p>
     * @param ie
     */
    public void interruptedException(InterruptedException ie) {
      LOG.debug(prefix("Received InterruptedException, doing nothing here"), ie);
      // At least preserver interrupt.
      Thread.currentThread().interrupt();
      // no-op
    }
  
    /**
     * Close the connection to ZooKeeper.
     * 
     * @throws InterruptedException
     */
    public void close() {
      try {
        if (recoverableZooKeeper != null) {
          recoverableZooKeeper.close();
        }
      } catch (InterruptedException e) {
        Thread.currentThread().interrupt();
      }
    }
  
    public Configuration getConfiguration() {
      return conf;
    }
  
    @Override
    public void abort(String why, Throwable e) {
      this.abortable.abort(why, e);
    }
  
    @Override
    public boolean isAborted() {
      return this.abortable.isAborted();
    }
  
    /**
     * @return Path to the currently active master.
     */
    public String getMasterAddressZNode() {
      return this.masterAddressZNode;
    }
  }
  