/**
*
* 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.client;
import java.io.Closeable;
import java.io.IOException;
import java.util.concurrent.ExecutorService;
import org.apache.hadoop.hbase.classification.InterfaceAudience;
import org.apache.hadoop.hbase.classification.InterfaceStability;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.Abortable;
import org.apache.hadoop.hbase.TableName;
/**
* A cluster connection encapsulating lower level individual connections to actual servers and
* a connection to zookeeper. Connections are instantiated through the {@link ConnectionFactory}
* class. The lifecycle of the connection is managed by the caller, who has to {@link #close()}
* the connection to release the resources.
*
* <p> The connection object contains logic to find the master, locate regions out on the cluster,
* keeps a cache of locations and then knows how to re-calibrate after they move. The individual
* connections to servers, meta cache, zookeeper connection, etc are all shared by the
* {@link Table} and {@link Admin} instances obtained from this connection.
*
* <p> Connection creation is a heavy-weight operation. Connection implementations are thread-safe,
* so that the client can create a connection once, and share it with different threads.
* {@link Table} and {@link Admin} instances, on the other hand, are light-weight and are not
* thread-safe. Typically, a single connection per client application is instantiated and every
* thread will obtain its own Table instance. Caching or pooling of {@link Table} and {@link Admin}
* is not recommended.
*
* <p>This class replaces {@link HConnection}, which is now deprecated.
* @see ConnectionFactory
* @since 0.99.0
*/
@InterfaceAudience.Public
@InterfaceStability.Evolving
public interface Connection extends Abortable, Closeable {
/*
* Implementation notes:
* - Only allow new style of interfaces:
* -- All table names are passed as TableName. No more byte[] and string arguments
* -- Most of the classes with names H is deprecated in favor of non-H versions
* (Table, Connection vs HConnection, etc)
* -- Only real client-facing public methods are allowed
* - Connection should contain only getTable(), getAdmin() kind of general methods.
*/
/**
* @return Configuration instance being used by this Connection instance.
*/
Configuration getConfiguration();
/**
* Retrieve a Table implementation for accessing a table.
* The returned Table is not thread safe, a new instance should be created for each using thread.
* This is a lightweight operation, pooling or caching of the returned Table
* is neither required nor desired.
* <br>
* The caller is responsible for calling {@link Table#close()} on the returned
* table instance.
*
* @param tableName the name of the table
* @return a Table to use for interactions with this table
*/
Table getTable(TableName tableName) throws IOException;
/**
* Retrieve a Table implementation for accessing a table.
* The returned Table is not thread safe, a new instance should be created for each using thread.
* This is a lightweight operation, pooling or caching of the returned Table
* is neither required nor desired.
* <br>
* The caller is responsible for calling {@link Table#close()} on the returned
* table instance.
*
* @param tableName the name of the table
* @param pool The thread pool to use for batch operations, null to use a default pool.
* @return a Table to use for interactions with this table
*/
Table getTable(TableName tableName, ExecutorService pool) throws IOException;
/**
* <p>
* Retrieve a {@link BufferedMutator} for performing client-side buffering of writes. The
* {@link BufferedMutator} returned by this method is thread-safe. This BufferedMutator will
* use the Connection's ExecutorService. This object can be used for long lived operations.
* </p>
* <p>
* The caller is responsible for calling {@link BufferedMutator#close()} on
* the returned {@link BufferedMutator} instance.
* </p>
* <p>
* This accessor will use the connection's ExecutorService and will throw an
* exception in the main thread when an asynchronous exception occurs.
*
* @param tableName the name of the table
*
* @return a {@link BufferedMutator} for the supplied tableName.
*/
public BufferedMutator getBufferedMutator(TableName tableName) throws IOException;
/**
* Retrieve a {@link BufferedMutator} for performing client-side buffering of writes. The
* {@link BufferedMutator} returned by this method is thread-safe. This object can be used for
* long lived table operations. The caller is responsible for calling
* {@link BufferedMutator#close()} on the returned {@link BufferedMutator} instance.
*
* @param params details on how to instantiate the {@code BufferedMutator}.
* @return a {@link BufferedMutator} for the supplied tableName.
*/
public BufferedMutator getBufferedMutator(BufferedMutatorParams params) throws IOException;
/**
* Retrieve a RegionLocator implementation to inspect region information on a table. The returned
* RegionLocator is not thread-safe, so a new instance should be created for each using thread.
*
* This is a lightweight operation. Pooling or caching of the returned RegionLocator is neither
* required nor desired.
* <br>
* The caller is responsible for calling {@link RegionLocator#close()} on the returned
* RegionLocator instance.
*
* RegionLocator needs to be unmanaged
*
* @param tableName Name of the table who's region is to be examined
* @return A RegionLocator instance
*/
public RegionLocator getRegionLocator(TableName tableName) throws IOException;
/**
* Retrieve an Admin implementation to administer an HBase cluster.
* The returned Admin is not guaranteed to be thread-safe. A new instance should be created for
* each using thread. This is a lightweight operation. Pooling or caching of the returned
* Admin is not recommended.
* <br>
* The caller is responsible for calling {@link Admin#close()} on the returned
* Admin instance.
*
* @return an Admin instance for cluster administration
*/
Admin getAdmin() throws IOException;
@Override
public void close() throws IOException;
/**
* Returns whether the connection is closed or not.
* @return true if this connection is closed
*/
boolean isClosed();
}