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.metrics.MetricRegistry;
027import org.apache.yetus.audience.InterfaceAudience;
028import org.apache.yetus.audience.InterfaceStability;
029
030@InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC)
031@InterfaceStability.Evolving
032public interface MasterCoprocessorEnvironment extends CoprocessorEnvironment<MasterCoprocessor> {
033  /** Returns Hosting Server's ServerName */
034  ServerName getServerName();
035
036  /**
037   * Returns the hosts' Connection to the Cluster. <b>Do not close! This is a shared connection with
038   * the hosting server. Throws {@link UnsupportedOperationException} if you try to close or abort
039   * it</b>. For light-weight usage only. Heavy-duty usage will pull down the hosting RegionServer
040   * responsiveness as well as that of other Coprocessors making use of this Connection. Use to
041   * create table on start or to do administrative operations. Coprocessors should create their own
042   * Connections if heavy usage to avoid impinging on hosting Server operation. To create a
043   * Connection or if a Coprocessor requires a region with a particular Configuration, use
044   * {@link org.apache.hadoop.hbase.client.ConnectionFactory} or
045   * {@link #createConnection(Configuration)}}.
046   * <p>
047   * Be aware that operations that make use of this Connection are executed as the RegionServer
048   * User, the hbase super user that started this server process. Exercise caution running
049   * operations as this User (See {@link #createConnection(Configuration)}} to run as other than the
050   * RegionServer User).
051   * <p>
052   * Be careful RPC'ing from a Coprocessor context. RPC's will fail, stall, retry, and/or crawl
053   * because the remote side is not online, is struggling or it is on the other side of a network
054   * partition. Any use of Connection from inside a Coprocessor must be able to handle all such
055   * hiccups.
056   * @see #createConnection(Configuration)
057   * @return The host's Connection to the Cluster.
058   */
059  Connection getConnection();
060
061  /**
062   * Creates a cluster connection using the passed Configuration. Creating a Connection is a
063   * heavy-weight operation. The resultant Connection's cache of region locations will be empty.
064   * Therefore you should cache and reuse Connections rather than create a Connection on demand.
065   * Create on start of your Coprocessor. You will have to cast the CoprocessorEnvironment
066   * appropriately to get at this API at start time because Coprocessor start method is passed a
067   * subclass of this CoprocessorEnvironment or fetch Connection using a synchronized accessor
068   * initializing the Connection on first access. Close the returned Connection when done to free
069   * resources. Using this API rather than
070   * {@link org.apache.hadoop.hbase.client.ConnectionFactory#createConnection(Configuration)}
071   * returns a Connection that will short-circuit RPC if the target is a local resource. Use
072   * ConnectionFactory if you don't need this ability.
073   * <p>
074   * Be careful RPC'ing from a Coprocessor context. RPC's will fail, stall, retry, and/or crawl
075   * because the remote side is not online, is struggling or it is on the other side of a network
076   * partition. Any use of Connection from inside a Coprocessor must be able to handle all such
077   * hiccups.
078   * @return Connection created using the passed conf.
079   */
080  Connection createConnection(Configuration conf) throws IOException;
081
082  /**
083   * Returns a MetricRegistry that can be used to track metrics at the master level.
084   * <p>
085   * See ExampleMasterObserverWithMetrics class in the hbase-examples modules for examples of how
086   * metrics can be instantiated and used.
087   * </p>
088   * @return A MetricRegistry for the coprocessor class to track and export metrics.
089   */
090  MetricRegistry getMetricRegistryForMaster();
091}