RootRegionTracker.java

/**
 * Copyright 2010 The Apache Software Foundation
 *
 * 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 org.apache.hadoop.hbase.zookeeper;

import org.apache.hadoop.hbase.Abortable;
import org.apache.hadoop.hbase.ServerName;
import org.apache.hadoop.hbase.catalog.RootLocationEditor;
import org.apache.hadoop.hbase.util.Addressing;
import org.apache.hadoop.hbase.util.Bytes;
import org.apache.zookeeper.KeeperException;

/**
 * Tracks the root region server location node in zookeeper.
 * Root region location is set by {@link RootLocationEditor} usually called
 * out of <code>RegionServerServices</code>.
 * This class has a watcher on the root location and notices changes.
 */
public class RootRegionTracker extends ZooKeeperNodeTracker {
  /**
   * Creates a root region location tracker.
   *
   * <p>After construction, use {@link #start} to kick off tracking.
   *
   * @param watcher
   * @param abortable
   */
  public RootRegionTracker(ZooKeeperWatcher watcher, Abortable abortable) {
    super(watcher, watcher.rootServerZNode, abortable);
  }

  /**
   * Checks if the root region location is available.
   * @return true if root region location is available, false if not
   */
  public boolean isLocationAvailable() {
    return super.getData(true) != null;
  }

  /**
   * Gets the root region location, if available.  Null if not.  Does not block.
   * @return server name
   * @throws InterruptedException
   */
  public ServerName getRootRegionLocation() throws InterruptedException {
    return dataToServerName(super.getData(true));
  }

  /**
   * Gets the root region location, if available, and waits for up to the
   * specified timeout if not immediately available.
   * Given the zookeeper notification could be delayed, we will try to
   * get the latest data.
   * @param timeout maximum time to wait, in millis
   * @return server name for server hosting root region formatted as per
   * {@link ServerName}, or null if none available
   * @throws InterruptedException if interrupted while waiting
   */
  public ServerName waitRootRegionLocation(long timeout)
  throws InterruptedException {
    if (false == checkIfBaseNodeAvailable()) {
      String errorMsg = "Check the value configured in 'zookeeper.znode.parent'. "
          + "There could be a mismatch with the one configured in the master.";
      LOG.error(errorMsg);
      throw new IllegalArgumentException(errorMsg);
    }
    return dataToServerName(super.blockUntilAvailable(timeout, true));
  }

  /*
   * @param data
   * @return Returns null if <code>data</code> is null else converts passed data
   * to a ServerName instance.
   */
  private static ServerName dataToServerName(final byte [] data) {
    // The str returned could be old style -- pre hbase-1502 -- which was
    // hostname and port seperated by a colon rather than hostname, port and
    // startcode delimited by a ','.
    if (data == null || data.length <= 0) return null;
    String str = Bytes.toString(data);
    int index = str.indexOf(ServerName.SERVERNAME_SEPARATOR);
    if (index != -1) {
      // Presume its ServerName.toString() format.
      return ServerName.parseServerName(str);
    }
    // Presume it a hostname:port format.
    String hostname = Addressing.parseHostname(str);
    int port = Addressing.parsePort(str);
    return new ServerName(hostname, port, -1L);
  }
}