001/*
002 *
003 * Licensed to the Apache Software Foundation (ASF) under one
004 * or more contributor license agreements.  See the NOTICE file
005 * distributed with this work for additional information
006 * regarding copyright ownership.  The ASF licenses this file
007 * to you under the Apache License, Version 2.0 (the
008 * "License"); you may not use this file except in compliance
009 * with the License.  You may obtain a copy of the License at
010 *
011 *     http://www.apache.org/licenses/LICENSE-2.0
012 *
013 * Unless required by applicable law or agreed to in writing, software
014 * distributed under the License is distributed on an "AS IS" BASIS,
015 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
016 * See the License for the specific language governing permissions and
017 * limitations under the License.
018 */
019package org.apache.hadoop.hbase;
020
021import org.apache.hadoop.conf.Configuration;
022import org.apache.hadoop.fs.FileSystem;
023import org.apache.hadoop.hbase.client.ClusterConnection;
024import org.apache.hadoop.hbase.client.Connection;
025import org.apache.hadoop.hbase.zookeeper.MetaTableLocator;
026import org.apache.hadoop.hbase.zookeeper.ZKWatcher;
027import org.apache.yetus.audience.InterfaceAudience;
028
029import java.io.IOException;
030
031/**
032 * Defines a curated set of shared functions implemented by HBase servers (Masters
033 * and RegionServers). For use internally only. Be judicious adding API. Changes cause ripples
034 * through the code base.
035 */
036@InterfaceAudience.Private
037public interface Server extends Abortable, Stoppable {
038  /**
039   * Gets the configuration object for this server.
040   */
041  Configuration getConfiguration();
042
043  /**
044   * Gets the ZooKeeper instance for this server.
045   */
046  ZKWatcher getZooKeeper();
047
048  /**
049   * Returns a reference to the servers' connection.
050   *
051   * Important note: this method returns a reference to Connection which is managed
052   * by Server itself, so callers must NOT attempt to close connection obtained.
053   */
054  Connection getConnection();
055
056  Connection createConnection(Configuration conf) throws IOException;
057
058  /**
059   * Returns a reference to the servers' cluster connection. Prefer {@link #getConnection()}.
060   *
061   * Important note: this method returns a reference to Connection which is managed
062   * by Server itself, so callers must NOT attempt to close connection obtained.
063   */
064  ClusterConnection getClusterConnection();
065
066  /**
067   * Returns instance of {@link org.apache.hadoop.hbase.zookeeper.MetaTableLocator}
068   * running inside this server. This MetaServerLocator is started and stopped by server, clients
069   * shouldn't manage it's lifecycle.
070   * @return instance of {@link MetaTableLocator} associated with this server.
071   */
072  MetaTableLocator getMetaTableLocator();
073
074  /**
075   * @return The unique server name for this server.
076   */
077  ServerName getServerName();
078
079  /**
080   * Get CoordinatedStateManager instance for this server.
081   */
082  CoordinatedStateManager getCoordinatedStateManager();
083
084  /**
085   * @return The {@link ChoreService} instance for this server
086   */
087  ChoreService getChoreService();
088
089  /**
090   * @return Return the FileSystem object used (can return null!).
091   */
092  // TODO: On Master, return Master's. On RegionServer, return RegionServers. The FileSystems
093  // may differ. TODO.
094  default FileSystem getFileSystem() {
095    // This default is pretty dodgy!
096    Configuration c = getConfiguration();
097    FileSystem fs = null;
098    try {
099      if (c != null) {
100        fs = FileSystem.get(c);
101      }
102    } catch (IOException e) {
103      // If an exception, just return null
104    }
105    return fs;
106  };
107
108  /**
109   * @return True is the server is Stopping
110   */
111  // Note: This method is not part of the Stoppable Interface.
112  default boolean isStopping() {
113    return false;
114  }
115}