hbase-client/src/main/java/org/apache/hadoop/hbase/client/Connection.java

   1 /**
   2  * Licensed to the Apache Software Foundation (ASF) under one
   3  * or more contributor license agreements.  See the NOTICE file
   4  * distributed with this work for additional information
   5  * regarding copyright ownership.  The ASF licenses this file
   6  * to you under the Apache License, Version 2.0 (the
   7  * "License"); you may not use this file except in compliance
   8  * with the License.  You may obtain a copy of the License at
   9  *
  10  *     http://www.apache.org/licenses/LICENSE-2.0
  11  *
  12  * Unless required by applicable law or agreed to in writing, software
  13  * distributed under the License is distributed on an "AS IS" BASIS,
  14  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  15  * See the License for the specific language governing permissions and
  16  * limitations under the License.
  17  */
  18 package org.apache.hadoop.hbase.client;
  19
  20 import java.io.Closeable;
  21 import java.io.IOException;
  22 import java.util.concurrent.ExecutorService;
  23 import org.apache.hadoop.conf.Configuration;
  24 import org.apache.hadoop.hbase.Abortable;
  25 import org.apache.hadoop.hbase.HBaseInterfaceAudience;
  26 import org.apache.hadoop.hbase.ServerName;
  27 import org.apache.hadoop.hbase.TableName;
  28 import org.apache.hadoop.hbase.util.FutureUtils;
  29 import org.apache.yetus.audience.InterfaceAudience;
  30
  31 /**
  32  * A cluster connection encapsulating lower level individual connections to actual servers and
  33  * a connection to zookeeper. Connections are instantiated through the {@link ConnectionFactory}
  34  * class. The lifecycle of the connection is managed by the caller, who has to {@link #close()}
  35  * the connection to release the resources.
  36  *
  37  * <p> The connection object contains logic to find the master, locate regions out on the cluster,
  38  * keeps a cache of locations and then knows how to re-calibrate after they move. The individual
  39  * connections to servers, meta cache, zookeeper connection, etc are all shared by the
  40  * {@link Table} and {@link Admin} instances obtained from this connection.
  41  *
  42  * <p> Connection creation is a heavy-weight operation. Connection implementations are thread-safe,
  43  * so that the client can create a connection once, and share it with different threads.
  44  * {@link Table} and {@link Admin} instances, on the other hand, are light-weight and are not
  45  * thread-safe.  Typically, a single connection per client application is instantiated and every
  46  * thread will obtain its own Table instance. Caching or pooling of {@link Table} and {@link Admin}
  47  * is not recommended.
  48  *
  49  * @see ConnectionFactory
  50  * @since 0.99.0
  51  */
  52 @InterfaceAudience.Public
  53 public interface Connection extends Abortable, Closeable {
  54
  55   /*
  56    * Implementation notes:
  57    *  - Only allow new style of interfaces:
  58    *   -- All table names are passed as TableName. No more byte[] and string arguments
  59    *   -- Most of the classes with names H is deprecated in favor of non-H versions
  60    *   (Table, Connection, etc)
  61    *   -- Only real client-facing public methods are allowed
  62    *  - Connection should contain only getTable(), getAdmin() kind of general methods.
  63    */
  64
  65   /**
  66    * @return Configuration instance being used by this Connection instance.
  67    */
  68   Configuration getConfiguration();
  69
  70   /**
  71    * Retrieve a Table implementation for accessing a table.
  72    * The returned Table is not thread safe, a new instance should be created for each using thread.
  73    * This is a lightweight operation, pooling or caching of the returned Table
  74    * is neither required nor desired.
  75    * <p>
  76    * The caller is responsible for calling {@link Table#close()} on the returned
  77    * table instance.
  78    * <p>
  79    * Since 0.98.1 this method no longer checks table existence. An exception
  80    * will be thrown if the table does not exist only when the first operation is
  81    * attempted.
  82    * @param tableName the name of the table
  83    * @return a Table to use for interactions with this table
  84    */
  85   default Table getTable(TableName tableName) throws IOException {
  86     return getTable(tableName, null);
  87   }
  88
  89   /**
  90    * Retrieve a Table implementation for accessing a table.
  91    * The returned Table is not thread safe, a new instance should be created for each using thread.
  92    * This is a lightweight operation, pooling or caching of the returned Table
  93    * is neither required nor desired.
  94    * <p>
  95    * The caller is responsible for calling {@link Table#close()} on the returned
  96    * table instance.
  97    * <p>
  98    * Since 0.98.1 this method no longer checks table existence. An exception
  99    * will be thrown if the table does not exist only when the first operation is
 100    * attempted.
 101    *
 102    * @param tableName the name of the table
 103    * @param pool The thread pool to use for batch operations, null to use a default pool.
 104    * @return a Table to use for interactions with this table
 105    */
 106   default Table getTable(TableName tableName, ExecutorService pool) throws IOException {
 107     return getTableBuilder(tableName, pool).build();
 108   }
 109
 110   /**
 111    * <p>
 112    * Retrieve a {@link BufferedMutator} for performing client-side buffering of writes. The
 113    * {@link BufferedMutator} returned by this method is thread-safe. This BufferedMutator will
 114    * use the Connection's ExecutorService. This object can be used for long lived operations.
 115    * </p>
 116    * <p>
 117    * The caller is responsible for calling {@link BufferedMutator#close()} on
 118    * the returned {@link BufferedMutator} instance.
 119    * </p>
 120    * <p>
 121    * This accessor will use the connection's ExecutorService and will throw an
 122    * exception in the main thread when an asynchronous exception occurs.
 123    *
 124    * @param tableName the name of the table
 125    *
 126    * @return a {@link BufferedMutator} for the supplied tableName.
 127    */
 128   default BufferedMutator getBufferedMutator(TableName tableName) throws IOException {
 129     return getBufferedMutator(new BufferedMutatorParams(tableName));
 130   }
 131
 132   /**
 133    * Retrieve a {@link BufferedMutator} for performing client-side buffering of writes. The
 134    * {@link BufferedMutator} returned by this method is thread-safe. This object can be used for
 135    * long lived table operations. The caller is responsible for calling
 136    * {@link BufferedMutator#close()} on the returned {@link BufferedMutator} instance.
 137    *
 138    * @param params details on how to instantiate the {@code BufferedMutator}.
 139    * @return a {@link BufferedMutator} for the supplied tableName.
 140    */
 141   BufferedMutator getBufferedMutator(BufferedMutatorParams params) throws IOException;
 142
 143   /**
 144    * Retrieve a RegionLocator implementation to inspect region information on a table. The returned
 145    * RegionLocator is not thread-safe, so a new instance should be created for each using thread.
 146    *
 147    * This is a lightweight operation.  Pooling or caching of the returned RegionLocator is neither
 148    * required nor desired.
 149    * <br>
 150    * The caller is responsible for calling {@link RegionLocator#close()} on the returned
 151    * RegionLocator instance.
 152    *
 153    * RegionLocator needs to be unmanaged
 154    *
 155    * @param tableName Name of the table who's region is to be examined
 156    * @return A RegionLocator instance
 157    */
 158   RegionLocator getRegionLocator(TableName tableName) throws IOException;
 159
 160   /**
 161    * Clear all the entries in the region location cache, for all the tables.
 162    * <p/>
 163    * If you only want to clear the cache for a specific table, use
 164    * {@link RegionLocator#clearRegionLocationCache()}.
 165    * <p/>
 166    * This may cause performance issue so use it with caution.
 167    */
 168   void clearRegionLocationCache();
 169
 170   /**
 171    * Retrieve an Admin implementation to administer an HBase cluster.
 172    * The returned Admin is not guaranteed to be thread-safe.  A new instance should be created for
 173    * each using thread.  This is a lightweight operation.  Pooling or caching of the returned
 174    * Admin is not recommended.
 175    * <br>
 176    * The caller is responsible for calling {@link Admin#close()} on the returned
 177    * Admin instance.
 178    *
 179    * @return an Admin instance for cluster administration
 180    */
 181   Admin getAdmin() throws IOException;
 182
 183   @Override
 184   void close() throws IOException;
 185
 186   /**
 187    * Returns whether the connection is closed or not.
 188    * @return true if this connection is closed
 189    */
 190   boolean isClosed();
 191
 192   /**
 193    * Returns an {@link TableBuilder} for creating {@link Table}.
 194    * @param tableName the name of the table
 195    * @param pool the thread pool to use for requests like batch and scan
 196    */
 197   TableBuilder getTableBuilder(TableName tableName, ExecutorService pool);
 198
 199   /**
 200    * Convert this connection to an {@link AsyncConnection}.
 201    * <p/>
 202    * Usually we will return the same instance if you call this method multiple times so you can
 203    * consider this as a light-weighted operation.
 204    */
 205   AsyncConnection toAsyncConnection();
 206
 207   /**
 208    * @return the cluster ID unique to this HBase cluster.
 209    */
 210   String getClusterId();
 211
 212   /**
 213    * Retrieve an Hbck implementation to fix an HBase cluster.
 214    * The returned Hbck is not guaranteed to be thread-safe. A new instance should be created by
 215    * each thread. This is a lightweight operation. Pooling or caching of the returned Hbck instance
 216    * is not recommended.
 217    * <br>
 218    * The caller is responsible for calling {@link Hbck#close()} on the returned Hbck instance.
 219    *<br>
 220    * This will be used mostly by hbck tool.
 221    *
 222    * @return an Hbck instance for active master. Active master is fetched from the zookeeper.
 223    */
 224   @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.HBCK)
 225   default Hbck getHbck() throws IOException {
 226     return FutureUtils.get(toAsyncConnection().getHbck());
 227   }
 228
 229   /**
 230    * Retrieve an Hbck implementation to fix an HBase cluster.
 231    * The returned Hbck is not guaranteed to be thread-safe. A new instance should be created by
 232    * each thread. This is a lightweight operation. Pooling or caching of the returned Hbck instance
 233    * is not recommended.
 234    * <br>
 235    * The caller is responsible for calling {@link Hbck#close()} on the returned Hbck instance.
 236    *<br>
 237    * This will be used mostly by hbck tool. This may only be used to by pass getting
 238    * registered master from ZK. In situations where ZK is not available or active master is not
 239    * registered with ZK and user can get master address by other means, master can be explicitly
 240    * specified.
 241    *
 242    * @param masterServer explicit {@link ServerName} for master server
 243    * @return an Hbck instance for a specified master server
 244    */
 245   @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.HBCK)
 246   default Hbck getHbck(ServerName masterServer) throws IOException {
 247     return toAsyncConnection().getHbck(masterServer);
 248   }
 249 }