001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018package org.apache.hadoop.hbase.coprocessor;
019
020import java.io.IOException;
021import org.apache.hadoop.conf.Configuration;
022import org.apache.hadoop.hbase.CoprocessorEnvironment;
023import org.apache.hadoop.hbase.HBaseInterfaceAudience;
024import org.apache.hadoop.hbase.ServerName;
025import org.apache.hadoop.hbase.client.Connection;
026import org.apache.hadoop.hbase.master.MasterServices;
027import org.apache.hadoop.hbase.metrics.MetricRegistry;
028import org.apache.yetus.audience.InterfaceAudience;
029import org.apache.yetus.audience.InterfaceStability;
030
031@InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC)
032@InterfaceStability.Evolving
033public interface MasterCoprocessorEnvironment extends CoprocessorEnvironment<MasterCoprocessor> {
034  /** Returns Hosting Server's ServerName */
035  ServerName getServerName();
036
037  /**
038   * Returns the hosts' Connection to the Cluster. <b>Do not close! This is a shared connection with
039   * the hosting server. Throws {@link UnsupportedOperationException} if you try to close or abort
040   * it</b>. For light-weight usage only. Heavy-duty usage will pull down the hosting RegionServer
041   * responsiveness as well as that of other Coprocessors making use of this Connection. Use to
042   * create table on start or to do administrative operations. Coprocessors should create their own
043   * Connections if heavy usage to avoid impinging on hosting Server operation. To create a
044   * Connection or if a Coprocessor requires a region with a particular Configuration, use
045   * {@link org.apache.hadoop.hbase.client.ConnectionFactory} or
046   * {@link #createConnection(Configuration)}}.
047   * <p>
048   * Be aware that operations that make use of this Connection are executed as the RegionServer
049   * User, the hbase super user that started this server process. Exercise caution running
050   * operations as this User (See {@link #createConnection(Configuration)}} to run as other than the
051   * RegionServer User).
052   * <p>
053   * Be careful RPC'ing from a Coprocessor context. RPC's will fail, stall, retry, and/or crawl
054   * because the remote side is not online, is struggling or it is on the other side of a network
055   * partition. Any use of Connection from inside a Coprocessor must be able to handle all such
056   * hiccups.
057   * @see #createConnection(Configuration)
058   * @return The host's Connection to the Cluster.
059   */
060  Connection getConnection();
061
062  /**
063   * Creates a cluster connection using the passed Configuration. Creating a Connection is a
064   * heavy-weight operation. The resultant Connection's cache of region locations will be empty.
065   * Therefore you should cache and reuse Connections rather than create a Connection on demand.
066   * Create on start of your Coprocessor. You will have to cast the CoprocessorEnvironment
067   * appropriately to get at this API at start time because Coprocessor start method is passed a
068   * subclass of this CoprocessorEnvironment or fetch Connection using a synchronized accessor
069   * initializing the Connection on first access. Close the returned Connection when done to free
070   * resources. Using this API rather than
071   * {@link org.apache.hadoop.hbase.client.ConnectionFactory#createConnection(Configuration)}
072   * returns a Connection that will short-circuit RPC if the target is a local resource. Use
073   * ConnectionFactory if you don't need this ability.
074   * <p>
075   * Be careful RPC'ing from a Coprocessor context. RPC's will fail, stall, retry, and/or crawl
076   * because the remote side is not online, is struggling or it is on the other side of a network
077   * partition. Any use of Connection from inside a Coprocessor must be able to handle all such
078   * hiccups.
079   * @return Connection created using the passed conf.
080   */
081  Connection createConnection(Configuration conf) throws IOException;
082
083  /**
084   * Returns a MetricRegistry that can be used to track metrics at the master level.
085   * <p>
086   * See ExampleMasterObserverWithMetrics class in the hbase-examples modules for examples of how
087   * metrics can be instantiated and used.
088   * </p>
089   * @return A MetricRegistry for the coprocessor class to track and export metrics.
090   */
091  MetricRegistry getMetricRegistryForMaster();
092
093  MasterServices getMasterServices();
094}