com.alibaba.wasp.zookeeper.ZKUtil.java Source code

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/**
 *
 * 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.DeserializationException;
import com.alibaba.wasp.ServerName;
import org.apache.commons.lang.StringUtils;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.EmptyWatcher;
import org.apache.hadoop.hbase.HConstants;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.hadoop.hbase.util.Threads;
import org.apache.hadoop.hbase.zookeeper.ZKConfig;
import org.apache.zookeeper.AsyncCallback;
import org.apache.zookeeper.CreateMode;
import org.apache.zookeeper.KeeperException;
import org.apache.zookeeper.Watcher;
import org.apache.zookeeper.ZooDefs.Ids;
import org.apache.zookeeper.ZooKeeper;
import org.apache.zookeeper.data.ACL;
import org.apache.zookeeper.data.Stat;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.InetSocketAddress;
import java.net.Socket;
import java.util.ArrayList;
import java.util.List;
import java.util.Properties;

/**
 * Internal Wasp utility class for ZooKeeper.
 * 
 * <p>
 * Contains only static methods and constants.
 * 
 * <p>
 * Methods all throw {@link org.apache.zookeeper.KeeperException} if there is an unexpected zookeeper
 * exception, so callers of these methods must handle appropriately. If ZK is
 * required for the operation, the server will need to be aborted.
 */
public class ZKUtil {
    private static final Log LOG = LogFactory.getLog(ZKUtil.class);

    // TODO: Replace this with ZooKeeper constant when ZOOKEEPER-277 is resolved.
    private static final char ZNODE_PATH_SEPARATOR = '/';
    private static int zkDumpConnectionTimeOut;

    /**
     * Creates a new connection to ZooKeeper, pulling settings and ensemble config
     * from the specified configuration object using methods from {@link org.apache.hadoop.hbase.zookeeper.ZKConfig}
     * .
     *
     * Sets the connection status monitoring watcher to the specified watcher.
     *
     * @param conf
     *          configuration to pull ensemble and other settings from
     * @param watcher
     *          watcher to monitor connection changes
     * @return connection to zookeeper
     * @throws java.io.IOException
     *           if unable to connect to zk or config problem
     */
    public static RecoverableZooKeeper connect(Configuration conf, Watcher watcher) throws IOException {
        Properties properties = ZKConfig.makeZKProps(conf);
        String ensemble = ZKConfig.getZKQuorumServersString(properties);
        return connect(conf, ensemble, watcher);
    }

    public static RecoverableZooKeeper connect(Configuration conf, String ensemble, Watcher watcher)
            throws IOException {
        return connect(conf, ensemble, watcher, "");
    }

    public static RecoverableZooKeeper connect(Configuration conf, String ensemble, Watcher watcher,
            final String descriptor) throws IOException {
        if (ensemble == null) {
            throw new IOException("Unable to determine ZooKeeper ensemble");
        }
        int timeout = conf.getInt(HConstants.ZK_SESSION_TIMEOUT, HConstants.DEFAULT_ZK_SESSION_TIMEOUT);
        LOG.debug(descriptor + " opening connection to ZooKeeper with ensemble (" + ensemble + ")");
        int retry = conf.getInt("zookeeper.recovery.retry", 3);
        int retryIntervalMillis = conf.getInt("zookeeper.recovery.retry.intervalmill", 1000);
        zkDumpConnectionTimeOut = conf.getInt("zookeeper.dump.connection.timeout", 1000);
        return new RecoverableZooKeeper(ensemble, timeout, watcher, retry, retryIntervalMillis);
    }

    //
    // Helper methods
    //

    /**
     * Join the prefix znode name with the suffix znode name to generate a proper
     * full znode name.
     *
     * Assumes prefix does not end with slash and suffix does not begin with it.
     *
     * @param prefix
     *          beginning of znode name
     * @param suffix
     *          ending of znode name
     * @return result of properly joining prefix with suffix
     */
    public static String joinZNode(String prefix, String suffix) {
        return prefix + ZNODE_PATH_SEPARATOR + suffix;
    }

    /**
     * Returns the full path of the immediate parent of the specified node.
     *
     * @param node
     *          path to get parent of
     * @return parent of path, null if passed the root node or an invalid node
     */
    public static String getParent(String node) {
        int idx = node.lastIndexOf(ZNODE_PATH_SEPARATOR);
        return idx <= 0 ? null : node.substring(0, idx);
    }

    /**
     * Get the name of the current node from the specified fully-qualified path.
     *
     * @param path
     *          fully-qualified path
     * @return name of the current node
     */
    public static String getNodeName(String path) {
        return path.substring(path.lastIndexOf("/") + 1);
    }

    /**
     * Get the key to the ZK ensemble for this configuration without adding a name
     * at the end
     *
     * @param conf
     *          Configuration to use to build the key
     * @return ensemble key without a name
     */
    public static String getZooKeeperClusterKey(Configuration conf) {
        return getZooKeeperClusterKey(conf, null);
    }

    /**
     * Get the key to the ZK ensemble for this configuration and append a name at
     * the end
     *
     * @param conf
     *          Configuration to use to build the key
     * @param name
     *          Name that should be appended at the end if not empty or null
     * @return ensemble key with a name (if any)
     */
    public static String getZooKeeperClusterKey(Configuration conf, String name) {
        String ensemble = conf.get(HConstants.ZOOKEEPER_QUORUM.replaceAll("[\\t\\n\\x0B\\f\\r]", ""));
        StringBuilder builder = new StringBuilder(ensemble);
        builder.append(":");
        builder.append(conf.get(HConstants.ZOOKEEPER_CLIENT_PORT));
        builder.append(":");
        builder.append(conf.get(HConstants.ZOOKEEPER_ZNODE_PARENT));
        if (name != null && !name.isEmpty()) {
            builder.append(",");
            builder.append(name);
        }
        return builder.toString();
    }

    /**
     * Apply the settings in the given key to the given configuration, this is
     * used to communicate with distant clusters
     *
     * @param conf
     *          configuration object to configure
     * @param key
     *          string that contains the 3 required configuratins
     * @throws java.io.IOException
     */
    public static void applyClusterKeyToConf(Configuration conf, String key) throws IOException {
        String[] parts = transformClusterKey(key);
        conf.set(HConstants.ZOOKEEPER_QUORUM, parts[0]);
        conf.set(HConstants.ZOOKEEPER_CLIENT_PORT, parts[1]);
        conf.set(HConstants.ZOOKEEPER_ZNODE_PARENT, parts[2]);
    }

    /**
     * Separate the given key into the three configurations it should contain:
     * hbase.zookeeper.quorum, hbase.zookeeper.client.port and
     * zookeeper.znode.parent
     *
     * @param key
     * @return the three configuration in the described order
     * @throws java.io.IOException
     */
    public static String[] transformClusterKey(String key) throws IOException {
        String[] parts = key.split(":");
        if (parts.length != 3) {
            throw new IOException("Cluster key invalid, the format should be:" + HConstants.ZOOKEEPER_QUORUM
                    + ":hbase.zookeeper.client.port:" + HConstants.ZOOKEEPER_ZNODE_PARENT);
        }
        return parts;
    }

    //
    // Existence checks and watches
    //

    /**
     * Watch the specified znode for delete/create/change events. The watcher is
     * set whether or not the node exists. If the node already exists, the method
     * returns true. If the node does not exist, the method returns false.
     *
     * @param zkw
     *          zk reference
     * @param znode
     *          path of node to watch
     * @return true if znode exists, false if does not exist or error
     * @throws org.apache.zookeeper.KeeperException
     *           if unexpected zookeeper exception
     */
    public static boolean watchAndCheckExists(ZooKeeperWatcher zkw, String znode) throws KeeperException {
        try {
            Stat s = zkw.getRecoverableZooKeeper().exists(znode, zkw);
            boolean exists = s != null ? true : false;
            if (exists) {
                LOG.debug(zkw.prefix("Set watcher on existing znode " + znode));
            } else {
                LOG.debug(zkw.prefix(znode + " does not exist. Watcher is set."));
            }
            return exists;
        } catch (KeeperException e) {
            LOG.warn(zkw.prefix("Unable to set watcher on znode " + znode), e);
            zkw.keeperException(e);
            return false;
        } catch (InterruptedException e) {
            LOG.warn(zkw.prefix("Unable to set watcher on znode " + znode), e);
            zkw.interruptedException(e);
            return false;
        }
    }

    /**
     * Check if the specified node exists. Sets no watches.
     *
     * @param zkw
     *          zk reference
     * @param znode
     *          path of node to watch
     * @return version of the node if it exists, -1 if does not exist
     * @throws org.apache.zookeeper.KeeperException
     *           if unexpected zookeeper exception
     */
    public static int checkExists(ZooKeeperWatcher zkw, String znode) throws KeeperException {
        try {
            Stat s = zkw.getRecoverableZooKeeper().exists(znode, null);
            return s != null ? s.getVersion() : -1;
        } catch (KeeperException e) {
            LOG.warn(zkw.prefix("Unable to set watcher on znode (" + znode + ")"), e);
            zkw.keeperException(e);
            return -1;
        } catch (InterruptedException e) {
            LOG.warn(zkw.prefix("Unable to set watcher on znode (" + znode + ")"), e);
            zkw.interruptedException(e);
            return -1;
        }
    }

    //
    // Znode listings
    //

    /**
     * Lists the children znodes of the specified znode. Also sets a watch on the
     * specified znode which will capture a NodeDeleted event on the specified
     * znode as well as NodeChildrenChanged if any children of the specified znode
     * are created or deleted.
     *
     * Returns null if the specified node does not exist. Otherwise returns a list
     * of children of the specified node. If the node exists but it has no
     * children, an empty list will be returned.
     *
     * @param zkw
     *          zk reference
     * @param znode
     *          path of node to list and watch children of
     * @return list of children of the specified node, an empty list if the node
     *         exists but has no children, and null if the node does not exist
     * @throws org.apache.zookeeper.KeeperException
     *           if unexpected zookeeper exception
     */
    public static List<String> listChildrenAndWatchForNewChildren(ZooKeeperWatcher zkw, String znode)
            throws KeeperException {
        try {
            List<String> children = zkw.getRecoverableZooKeeper().getChildren(znode, zkw);
            return children;
        } catch (KeeperException.NoNodeException ke) {
            LOG.debug(zkw.prefix("Unable to list children of znode " + znode + " "
                    + "because node does not exist (not an error)"));
            return null;
        } catch (KeeperException e) {
            LOG.warn(zkw.prefix("Unable to list children of znode " + znode + " "), e);
            zkw.keeperException(e);
            return null;
        } catch (InterruptedException e) {
            LOG.warn(zkw.prefix("Unable to list children of znode " + znode + " "), e);
            zkw.interruptedException(e);
            return null;
        }
    }

    /**
     * List all the children of the specified znode, setting a watch for children
     * changes and also setting a watch on every individual child in order to get
     * the NodeCreated and NodeDeleted events.
     *
     * @param zkw
     *          zookeeper reference
     * @param znode
     *          node to get children of and watch
     * @return list of znode names, null if the node doesn't exist
     * @throws org.apache.zookeeper.KeeperException
     */
    public static List<String> listChildrenAndWatchThem(ZooKeeperWatcher zkw, String znode) throws KeeperException {
        List<String> children = listChildrenAndWatchForNewChildren(zkw, znode);
        if (children == null) {
            return null;
        }
        for (String child : children) {
            watchAndCheckExists(zkw, joinZNode(znode, child));
        }
        return children;
    }

    /**
     * Lists the children of the specified znode without setting any watches.
     *
     * Used to list the currently online fservers and their addresses.
     *
     * Sets no watches at all, this method is best effort.
     *
     * Returns an empty list if the node has no children. Returns null if the
     * parent node itself does not exist.
     *
     * @param zkw
     *          zookeeper reference
     * @param znode
     *          node to get children of as addresses
     * @return list of data of children of specified znode, empty if no children,
     *         null if parent does not exist
     * @throws org.apache.zookeeper.KeeperException
     *           if unexpected zookeeper exception
     */
    public static List<String> listChildrenNoWatch(ZooKeeperWatcher zkw, String znode) throws KeeperException {
        List<String> children = null;
        try {
            // List the children without watching
            children = zkw.getRecoverableZooKeeper().getChildren(znode, null);
        } catch (KeeperException.NoNodeException nne) {
            return null;
        } catch (InterruptedException ie) {
            zkw.interruptedException(ie);
        }
        return children;
    }

    /**
     * Checks if the specified znode has any children. Sets no watches.
     *
     * Returns true if the node exists and has children. Returns false if the node
     * does not exist or if the node does not have any children.
     *
     * Used during master initialization to determine if the master is a
     * failed-over-to master or the first master during initial cluster startup.
     * If the directory for fserver ephemeral nodes is empty then this is a
     * cluster startup, if not then it is not cluster startup.
     *
     * @param zkw
     *          zk reference
     * @param znode
     *          path of node to check for children of
     * @return true if node has children, false if not or node does not exist
     * @throws org.apache.zookeeper.KeeperException
     *           if unexpected zookeeper exception
     */
    public static boolean nodeHasChildren(ZooKeeperWatcher zkw, String znode) throws KeeperException {
        try {
            return !zkw.getRecoverableZooKeeper().getChildren(znode, null).isEmpty();
        } catch (KeeperException.NoNodeException ke) {
            LOG.debug(zkw.prefix("Unable to list children of znode " + znode + " "
                    + "because node does not exist (not an error)"));
            return false;
        } catch (KeeperException e) {
            LOG.warn(zkw.prefix("Unable to list children of znode " + znode), e);
            zkw.keeperException(e);
            return false;
        } catch (InterruptedException e) {
            LOG.warn(zkw.prefix("Unable to list children of znode " + znode), e);
            zkw.interruptedException(e);
            return false;
        }
    }

    /**
     * Get the number of children of the specified node.
     *
     * If the node does not exist or has no children, returns 0.
     *
     * Sets no watches at all.
     *
     * @param zkw
     *          zk reference
     * @param znode
     *          path of node to count children of
     * @return number of children of specified node, 0 if none or parent does not
     *         exist
     * @throws org.apache.zookeeper.KeeperException
     *           if unexpected zookeeper exception
     */
    public static int getNumberOfChildren(ZooKeeperWatcher zkw, String znode) throws KeeperException {
        try {
            Stat stat = zkw.getRecoverableZooKeeper().exists(znode, null);
            return stat == null ? 0 : stat.getNumChildren();
        } catch (KeeperException e) {
            LOG.warn(zkw.prefix("Unable to get children of node " + znode));
            zkw.keeperException(e);
        } catch (InterruptedException e) {
            zkw.interruptedException(e);
        }
        return 0;
    }

    //
    // Data retrieval
    //

    /**
     * Get znode data. Does not set a watcher.
     *
     * @return ZNode data, null if the node does not exist or if there is an
     *         error.
     */
    public static byte[] getData(ZooKeeperWatcher zkw, String znode) throws KeeperException {
        try {
            byte[] data = zkw.getRecoverableZooKeeper().getData(znode, null, null);
            logRetrievedMsg(zkw, znode, data, false);
            return data;
        } catch (KeeperException.NoNodeException e) {
            LOG.debug(zkw.prefix(
                    "Unable to get data of znode " + znode + " " + "because node does not exist (not an error)"));
            return null;
        } catch (KeeperException e) {
            LOG.warn(zkw.prefix("Unable to get data of znode " + znode), e);
            zkw.keeperException(e);
            return null;
        } catch (InterruptedException e) {
            LOG.warn(zkw.prefix("Unable to get data of znode " + znode), e);
            zkw.interruptedException(e);
            return null;
        }
    }

    /**
     * Get the data at the specified znode and set a watch.
     *
     * Returns the data and sets a watch if the node exists. Returns null and no
     * watch is set if the node does not exist or there is an exception.
     *
     * @param zkw
     *          zk reference
     * @param znode
     *          path of node
     * @return data of the specified znode, or null
     * @throws org.apache.zookeeper.KeeperException
     *           if unexpected zookeeper exception
     */
    public static byte[] getDataAndWatch(ZooKeeperWatcher zkw, String znode) throws KeeperException {
        return getDataInternal(zkw, znode, null, true);
    }

    /**
     * Get the data at the specified znode and set a watch.
     *
     * Returns the data and sets a watch if the node exists. Returns null and no
     * watch is set if the node does not exist or there is an exception.
     *
     * @param zkw
     *          zk reference
     * @param znode
     *          path of node
     * @param stat
     *          object to populate the version of the znode
     * @return data of the specified znode, or null
     * @throws org.apache.zookeeper.KeeperException
     *           if unexpected zookeeper exception
     */
    public static byte[] getDataAndWatch(ZooKeeperWatcher zkw, String znode, Stat stat) throws KeeperException {
        return getDataInternal(zkw, znode, stat, true);
    }

    private static byte[] getDataInternal(ZooKeeperWatcher zkw, String znode, Stat stat, boolean watcherSet)
            throws KeeperException {
        try {
            byte[] data = zkw.getRecoverableZooKeeper().getData(znode, zkw, stat);
            logRetrievedMsg(zkw, znode, data, watcherSet);
            return data;
        } catch (KeeperException.NoNodeException e) {
            // This log can get pretty annoying when we cycle on 100ms waits.
            // Enable trace if you really want to see it.
            LOG.trace(zkw.prefix(
                    "Unable to get data of znode " + znode + " " + "because node does not exist (not an error)"));
            return null;
        } catch (KeeperException e) {
            LOG.warn(zkw.prefix("Unable to get data of znode " + znode), e);
            zkw.keeperException(e);
            return null;
        } catch (InterruptedException e) {
            LOG.warn(zkw.prefix("Unable to get data of znode " + znode), e);
            zkw.interruptedException(e);
            return null;
        }
    }

    /**
     * Get the data at the specified znode without setting a watch.
     *
     * Returns the data if the node exists. Returns null if the node does not
     * exist.
     *
     * Sets the stats of the node in the passed Stat object. Pass a null stat if
     * not interested.
     *
     * @param zkw
     *          zk reference
     * @param znode
     *          path of node
     * @param stat
     *          node status to get if node exists
     * @return data of the specified znode, or null if node does not exist
     * @throws org.apache.zookeeper.KeeperException
     *           if unexpected zookeeper exception
     */
    public static byte[] getDataNoWatch(ZooKeeperWatcher zkw, String znode, Stat stat) throws KeeperException {
        try {
            byte[] data = zkw.getRecoverableZooKeeper().getData(znode, null, stat);
            logRetrievedMsg(zkw, znode, data, false);
            return data;
        } catch (KeeperException.NoNodeException e) {
            LOG.debug(zkw.prefix("Unable to get data of znode " + znode + " "
                    + "because node does not exist (not necessarily an error)"));
            return null;
        } catch (KeeperException e) {
            LOG.warn(zkw.prefix("Unable to get data of znode " + znode), e);
            zkw.keeperException(e);
            return null;
        } catch (InterruptedException e) {
            LOG.warn(zkw.prefix("Unable to get data of znode " + znode), e);
            zkw.interruptedException(e);
            return null;
        }
    }

    //
    // Data setting
    //

    /**
     * Sets the data of the existing znode to be the specified data. Ensures that
     * the current data has the specified expected version.
     *
     * <p>
     * If the node does not exist, a {@link org.apache.zookeeper.KeeperException.NoNodeException} will be thrown.
     *
     * <p>
     * If their is a version mismatch, method returns null.
     *
     * <p>
     * No watches are set but setting data will trigger other watchers of this
     * node.
     *
     * <p>
     * If there is another problem, a KeeperException will be thrown.
     *
     * @param zkw
     *          zk reference
     * @param znode
     *          path of node
     * @param data
     *          data to set for node
     * @param expectedVersion
     *          version expected when setting data
     * @return true if data set, false if version mismatch
     * @throws org.apache.zookeeper.KeeperException
     *           if unexpected zookeeper exception
     */
    public static boolean setData(ZooKeeperWatcher zkw, String znode, byte[] data, int expectedVersion)
            throws KeeperException, KeeperException.NoNodeException {
        try {
            return zkw.getRecoverableZooKeeper().setData(znode, data, expectedVersion) != null;
        } catch (InterruptedException e) {
            zkw.interruptedException(e);
            return false;
        }
    }

    /**
     * Set data into node creating node if it doesn't yet exist. Does not set
     * watch.
     *
     * @param zkw
     *          zk reference
     * @param znode
     *          path of node
     * @param data
     *          data to set for node
     * @throws org.apache.zookeeper.KeeperException
     */
    public static void createSetData(final ZooKeeperWatcher zkw, final String znode, final byte[] data)
            throws KeeperException {
        if (checkExists(zkw, znode) == -1) {
            ZKUtil.createWithParents(zkw, znode);
        }
        ZKUtil.setData(zkw, znode, data);
    }

    /**
     * Sets the data of the existing znode to be the specified data. The node must
     * exist but no checks are done on the existing data or version.
     *
     * <p>
     * If the node does not exist, a {@link org.apache.zookeeper.KeeperException.NoNodeException} will be thrown.
     *
     * <p>
     * No watches are set but setting data will trigger other watchers of this
     * node.
     *
     * <p>
     * If there is another problem, a KeeperException will be thrown.
     *
     * @param zkw
     *          zk reference
     * @param znode
     *          path of node
     * @param data
     *          data to set for node
     * @throws org.apache.zookeeper.KeeperException
     *           if unexpected zookeeper exception
     */
    public static void setData(ZooKeeperWatcher zkw, String znode, byte[] data)
            throws KeeperException, KeeperException.NoNodeException {
        setData(zkw, znode, data, -1);
    }

    public static boolean isSecureZooKeeper(Configuration conf) {
        // TODO: We need a better check for security enabled ZooKeeper. Currently
        // the secure ZooKeeper client is set up using a supplied JaaS
        // configuration file. But if the system property for the JaaS
        // configuration file is set, this may not be an exclusive indication
        // that HBase should set ACLs on znodes. As an alternative, we could do
        // this more like Hadoop and build a JaaS configuration programmatically
        // based on a site conf setting. The scope of such a change will be
        // addressed in HBASE-4791.
        return (System.getProperty("java.security.auth.login.config") != null);
    }

    private static ArrayList<ACL> createACL(ZooKeeperWatcher zkw, String node) {
        if (isSecureZooKeeper(zkw.getConfiguration())) {
            // Certain znodes are accessed directly by the client,
            // so they must be readable by non-authenticated clients
            if ((node.equals(zkw.baseZNode) == true) || (node.equals(zkw.getMasterAddressZNode()) == true)
                    || (node.equals(zkw.clusterIdZNode) == true) || (node.equals(zkw.fsZNode) == true)
                    || (node.equals(zkw.backupMasterAddressesZNode) == true)
                    || (node.startsWith(zkw.tableZNode) == true)) {
                return ZooKeeperWatcher.CREATOR_ALL_AND_WORLD_READABLE;
            }
            return Ids.CREATOR_ALL_ACL;
        } else {
            return Ids.OPEN_ACL_UNSAFE;
        }
    }

    public static void waitForZKConnectionIfAuthenticating(ZooKeeperWatcher zkw) throws InterruptedException {
        if (isSecureZooKeeper(zkw.getConfiguration())) {
            LOG.debug("Waiting for ZooKeeperWatcher to authenticate");
            zkw.saslLatch.await();
            LOG.debug("Done waiting.");
        }
    }

    //
    // Node creation
    //

    /**
     *
     * Set the specified znode to be an ephemeral node carrying the specified
     * data.
     *
     * If the node is created successfully, a watcher is also set on the node.
     *
     * If the node is not created successfully because it already exists, this
     * method will also set a watcher on the node.
     *
     * If there is another problem, a KeeperException will be thrown.
     *
     * @param zkw
     *          zk reference
     * @param znode
     *          path of node
     * @param data
     *          data of node
     * @return true if node created, false if not, watch set in both cases
     * @throws org.apache.zookeeper.KeeperException
     *           if unexpected zookeeper exception
     */
    public static boolean createEphemeralNodeAndWatch(ZooKeeperWatcher zkw, String znode, byte[] data)
            throws KeeperException {
        try {
            waitForZKConnectionIfAuthenticating(zkw);
            zkw.getRecoverableZooKeeper().create(znode, data, createACL(zkw, znode), CreateMode.EPHEMERAL);
        } catch (KeeperException.NodeExistsException nee) {
            if (!watchAndCheckExists(zkw, znode)) {
                // It did exist but now it doesn't, try again
                return createEphemeralNodeAndWatch(zkw, znode, data);
            }
            return false;
        } catch (InterruptedException e) {
            LOG.info("Interrupted", e);
            Thread.currentThread().interrupt();
        }
        return true;
    }

    /**
     * Creates the specified znode to be a persistent node carrying the specified
     * data.
     *
     * Returns true if the node was successfully created, false if the node
     * already existed.
     *
     * If the node is created successfully, a watcher is also set on the node.
     *
     * If the node is not created successfully because it already exists, this
     * method will also set a watcher on the node but return false.
     *
     * If there is another problem, a KeeperException will be thrown.
     *
     * @param zkw
     *          zk reference
     * @param znode
     *          path of node
     * @param data
     *          data of node
     * @return true if node created, false if not, watch set in both cases
     * @throws org.apache.zookeeper.KeeperException
     *           if unexpected zookeeper exception
     */
    public static boolean createNodeIfNotExistsAndWatch(ZooKeeperWatcher zkw, String znode, byte[] data)
            throws KeeperException {
        try {
            waitForZKConnectionIfAuthenticating(zkw);
            zkw.getRecoverableZooKeeper().create(znode, data, createACL(zkw, znode), CreateMode.PERSISTENT);
        } catch (KeeperException.NodeExistsException nee) {
            try {
                zkw.getRecoverableZooKeeper().exists(znode, zkw);
            } catch (InterruptedException e) {
                zkw.interruptedException(e);
                return false;
            }
            return false;
        } catch (InterruptedException e) {
            zkw.interruptedException(e);
            return false;
        }
        return true;
    }

    /**
     * Creates the specified node with the specified data and watches it.
     *
     * <p>
     * Throws an exception if the node already exists.
     *
     * <p>
     * The node created is persistent and open access.
     *
     * <p>
     * Returns the version number of the created node if successful.
     *
     * @param zkw
     *          zk reference
     * @param znode
     *          path of node to create
     * @param data
     *          data of node to create
     * @return version of node created
     * @throws org.apache.zookeeper.KeeperException
     *           if unexpected zookeeper exception
     * @throws org.apache.zookeeper.KeeperException.NodeExistsException
     *           if node already exists
     */
    public static int createAndWatch(ZooKeeperWatcher zkw, String znode, byte[] data)
            throws KeeperException, KeeperException.NodeExistsException {
        try {
            waitForZKConnectionIfAuthenticating(zkw);
            zkw.getRecoverableZooKeeper().create(znode, data, createACL(zkw, znode), CreateMode.PERSISTENT);
            return zkw.getRecoverableZooKeeper().exists(znode, zkw).getVersion();
        } catch (InterruptedException e) {
            zkw.interruptedException(e);
            return -1;
        }
    }

    /**
     * Async creates the specified node with the specified data.
     *
     * <p>
     * Throws an exception if the node already exists.
     *
     * <p>
     * The node created is persistent and open access.
     *
     * @param zkw
     *          zk reference
     * @param znode
     *          path of node to create
     * @param data
     *          data of node to create
     * @param cb
     * @param ctx
     * @throws org.apache.zookeeper.KeeperException
     *           if unexpected zookeeper exception
     * @throws org.apache.zookeeper.KeeperException.NodeExistsException
     *           if node already exists
     */
    public static void asyncCreate(ZooKeeperWatcher zkw, String znode, byte[] data,
            final AsyncCallback.StringCallback cb, final Object ctx) {
        try {
            waitForZKConnectionIfAuthenticating(zkw);
            zkw.getRecoverableZooKeeper().getZooKeeper().create(znode, data, createACL(zkw, znode),
                    CreateMode.PERSISTENT, cb, ctx);
        } catch (InterruptedException e) {
            zkw.interruptedException(e);
        }
    }

    /**
     * Creates the specified node, if the node does not exist. Does not set a
     * watch and fails silently if the node already exists.
     *
     * The node created is persistent and open access.
     *
     * @param zkw
     *          zk reference
     * @param znode
     *          path of node
     * @throws org.apache.zookeeper.KeeperException
     *           if unexpected zookeeper exception
     */
    public static void createAndFailSilent(ZooKeeperWatcher zkw, String znode) throws KeeperException {
        try {
            RecoverableZooKeeper zk = zkw.getRecoverableZooKeeper();
            waitForZKConnectionIfAuthenticating(zkw);
            if (zk.exists(znode, false) == null) {
                zk.create(znode, new byte[0], createACL(zkw, znode), CreateMode.PERSISTENT);
            }
        } catch (KeeperException.NodeExistsException nee) {
        } catch (KeeperException.NoAuthException nee) {
            try {
                if (null == zkw.getRecoverableZooKeeper().exists(znode, false)) {
                    // If we failed to create the file and it does not already exist.
                    throw (nee);
                }
            } catch (InterruptedException ie) {
                zkw.interruptedException(ie);
            }

        } catch (InterruptedException ie) {
            zkw.interruptedException(ie);
        }
    }

    /**
     * Creates the specified node and all parent nodes required for it to exist.
     *
     * No watches are set and no errors are thrown if the node already exists.
     *
     * The nodes created are persistent and open access.
     *
     * @param zkw
     *          zk reference
     * @param znode
     *          path of node
     * @throws org.apache.zookeeper.KeeperException
     *           if unexpected zookeeper exception
     */
    public static void createWithParents(ZooKeeperWatcher zkw, String znode) throws KeeperException {
        try {
            if (znode == null) {
                return;
            }
            waitForZKConnectionIfAuthenticating(zkw);
            zkw.getRecoverableZooKeeper().create(znode, new byte[0], createACL(zkw, znode), CreateMode.PERSISTENT);
        } catch (KeeperException.NodeExistsException nee) {
            return;
        } catch (KeeperException.NoNodeException nne) {
            createWithParents(zkw, getParent(znode));
            createWithParents(zkw, znode);
        } catch (InterruptedException ie) {
            zkw.interruptedException(ie);
        }
    }

    //
    // Deletes
    //

    /**
     * Delete the specified node. Sets no watches. Throws all exceptions.
     */
    public static void deleteNode(ZooKeeperWatcher zkw, String node) throws KeeperException {
        deleteNode(zkw, node, -1);
    }

    /**
     * Delete the specified node with the specified version. Sets no watches.
     * Throws all exceptions.
     */
    public static boolean deleteNode(ZooKeeperWatcher zkw, String node, int version) throws KeeperException {
        try {
            zkw.getRecoverableZooKeeper().delete(node, version);
            return true;
        } catch (KeeperException.BadVersionException bve) {
            return false;
        } catch (InterruptedException ie) {
            zkw.interruptedException(ie);
            return false;
        }
    }

    /**
     * Deletes the specified node. Fails silent if the node does not exist.
     *
     * @param zkw
     * @param node
     * @throws org.apache.zookeeper.KeeperException
     */
    public static void deleteNodeFailSilent(ZooKeeperWatcher zkw, String node) throws KeeperException {
        try {
            zkw.getRecoverableZooKeeper().delete(node, -1);
        } catch (KeeperException.NoNodeException nne) {
        } catch (InterruptedException ie) {
            zkw.interruptedException(ie);
        }
    }

    /**
     * Delete the specified node and all of it's children.
     * <p>
     * If the node does not exist, just returns.
     * <p>
     * Sets no watches. Throws all exceptions besides dealing with deletion of
     * children.
     */
    public static void deleteNodeRecursively(ZooKeeperWatcher zkw, String node) throws KeeperException {
        try {
            List<String> children = ZKUtil.listChildrenNoWatch(zkw, node);
            // the node is already deleted, so we just finish
            if (children == null)
                return;

            if (!children.isEmpty()) {
                for (String child : children) {
                    deleteNodeRecursively(zkw, joinZNode(node, child));
                }
            }
            zkw.getRecoverableZooKeeper().delete(node, -1);
        } catch (InterruptedException ie) {
            zkw.interruptedException(ie);
        }
    }

    /**
     * Delete all the children of the specified node but not the node itself.
     *
     * Sets no watches. Throws all exceptions besides dealing with deletion of
     * children.
     */
    public static void deleteChildrenRecursively(ZooKeeperWatcher zkw, String node) throws KeeperException {
        List<String> children = ZKUtil.listChildrenNoWatch(zkw, node);
        if (children == null || children.isEmpty())
            return;
        for (String child : children) {
            deleteNodeRecursively(zkw, joinZNode(node, child));
        }
    }

    //
    // ZooKeeper cluster information
    //

    /** @return String dump of everything in ZooKeeper. */
    public static String dump(ZooKeeperWatcher zkw) {
        StringBuilder sb = new StringBuilder();
        try {
            sb.append("Wasp is rooted at ").append(zkw.baseZNode);
            sb.append("\nActive master address: ");
            try {
                sb.append(MasterAddressTracker.getMasterAddress(zkw));
            } catch (IOException e) {
                sb.append("<<FAILED LOOKUP: " + e.getMessage() + ">>");
            }
            sb.append("\nBackup master addresses:");
            for (String child : listChildrenNoWatch(zkw, zkw.backupMasterAddressesZNode)) {
                sb.append("\n ").append(child);
            }
            sb.append("\nFServers:");
            for (String child : listChildrenNoWatch(zkw, zkw.fsZNode)) {
                sb.append("\n ").append(child);
            }
            sb.append("\nQuorum Server Statistics:");
            String[] servers = zkw.getQuorum().split(",");
            for (String server : servers) {
                sb.append("\n ").append(server);
                try {
                    String[] stat = getServerStats(server, ZKUtil.zkDumpConnectionTimeOut);

                    if (stat == null) {
                        sb.append("[Error] invalid quorum server: " + server);
                        break;
                    }

                    for (String s : stat) {
                        sb.append("\n  ").append(s);
                    }
                } catch (Exception e) {
                    sb.append("\n  ERROR: ").append(e.getMessage());
                }
            }
        } catch (KeeperException ke) {
            sb.append("\nFATAL ZooKeeper Exception!\n");
            sb.append("\n" + ke.getMessage());
        }
        return sb.toString();
    }

    /**
     * Gets the statistics from the given server.
     *
     * @param server
     *          The server to get the statistics from.
     * @param timeout
     *          The socket timeout to use.
     * @return The array of response strings.
     * @throws java.io.IOException
     *           When the socket communication fails.
     */
    public static String[] getServerStats(String server, int timeout) throws IOException {
        String[] sp = server.split(":");
        if (sp == null || sp.length == 0) {
            return null;
        }

        String host = sp[0];
        int port = sp.length > 1 ? Integer.parseInt(sp[1]) : HConstants.DEFAULT_ZOOKEPER_CLIENT_PORT;

        Socket socket = new Socket();
        InetSocketAddress sockAddr = new InetSocketAddress(host, port);
        socket.connect(sockAddr, timeout);

        socket.setSoTimeout(timeout);
        PrintWriter out = new PrintWriter(socket.getOutputStream(), true);
        BufferedReader in = new BufferedReader(new InputStreamReader(socket.getInputStream()));
        out.println("stat");
        out.flush();
        ArrayList<String> res = new ArrayList<String>();
        while (true) {
            String line = in.readLine();
            if (line != null) {
                res.add(line);
            } else {
                break;
            }
        }
        socket.close();
        return res.toArray(new String[res.size()]);
    }

    private static void logRetrievedMsg(final ZooKeeperWatcher zkw, final String znode, final byte[] data,
            final boolean watcherSet) {
        if (!LOG.isDebugEnabled())
            return;
        LOG.debug(zkw.prefix("Retrieved " + ((data == null) ? 0 : data.length) + " byte(s) of data from znode "
                + znode + (watcherSet ? " and set watcher; " : "; data=")
                + (data == null ? "null"
                        : data.length == 0 ? "empty"
                                : (znode.startsWith(zkw.assignmentZNode) ? ZKAssign.toString(data) : // We should not be doing this
                                // reaching into another class
                                        znode.startsWith(zkw.backupMasterAddressesZNode)
                                                ? getServerNameOrEmptyString(data)
                                                : StringUtils.abbreviate(Bytes.toStringBinary(data), 32)))));
    }

    private static String getServerNameOrEmptyString(final byte[] data) {
        try {
            return ServerName.parseFrom(data).toString();
        } catch (DeserializationException e) {
            return "";
        }
    }

    /**
     * Waits for HBase installation's base (parent) znode to become available.
     *
     * @throws java.io.IOException
     *           on ZK errors
     */
    public static void waitForBaseZNode(Configuration conf) throws IOException {
        LOG.info("Waiting until the base znode is available");
        String parentZNode = conf.get(HConstants.ZOOKEEPER_ZNODE_PARENT, HConstants.DEFAULT_ZOOKEEPER_ZNODE_PARENT);
        ZooKeeper zk = new ZooKeeper(ZKConfig.getZKQuorumServersString(conf),
                conf.getInt(HConstants.ZK_SESSION_TIMEOUT, HConstants.DEFAULT_ZK_SESSION_TIMEOUT),
                EmptyWatcher.instance);

        final int maxTimeMs = 10000;
        final int maxNumAttempts = maxTimeMs / HConstants.SOCKET_RETRY_WAIT_MS;

        KeeperException keeperEx = null;
        try {
            try {
                for (int attempt = 0; attempt < maxNumAttempts; ++attempt) {
                    try {
                        if (zk.exists(parentZNode, false) != null) {
                            LOG.info("Parent znode exists: " + parentZNode);
                            keeperEx = null;
                            break;
                        }
                    } catch (KeeperException e) {
                        keeperEx = e;
                    }
                    Threads.sleepWithoutInterrupt(HConstants.SOCKET_RETRY_WAIT_MS);
                }
            } finally {
                zk.close();
            }
        } catch (InterruptedException ex) {
            Thread.currentThread().interrupt();
        }

        if (keeperEx != null) {
            throw new IOException(keeperEx);
        }
    }

    public static byte[] blockUntilAvailable(final ZooKeeperWatcher zkw, final String znode, final long timeout)
            throws InterruptedException {
        if (timeout < 0)
            throw new IllegalArgumentException();
        if (zkw == null)
            throw new IllegalArgumentException();
        if (znode == null)
            throw new IllegalArgumentException();

        byte[] data = null;
        boolean finished = false;
        final long endTime = System.currentTimeMillis() + timeout;
        while (!finished) {
            try {
                data = ZKUtil.getData(zkw, znode);
            } catch (KeeperException e) {
                LOG.warn("Unexpected exception handling blockUntilAvailable", e);
            }

            if (data == null && (System.currentTimeMillis() + HConstants.SOCKET_RETRY_WAIT_MS < endTime)) {
                Thread.sleep(HConstants.SOCKET_RETRY_WAIT_MS);
            } else {
                finished = true;
            }
        }

        return data;
    }

    /**
     * Convert a {@link com.alibaba.wasp.DeserializationException} to a more palatable
     * {@link org.apache.zookeeper.KeeperException}. Used when can't let a
     * {@link com.alibaba.wasp.DeserializationException} out w/o changing public API.
     * 
     * @param e
     *          Exception to convert
     * @return Converted exception
     */
    public static KeeperException convert(final DeserializationException e) {
        KeeperException ke = new KeeperException.DataInconsistencyException();
        ke.initCause(e);
        return ke;
    }
}