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 */
019
020package org.apache.hadoop.hbase.coprocessor;
021
022import java.io.IOException;
023import java.util.concurrent.ConcurrentMap;
024
025import org.apache.hadoop.conf.Configuration;
026import org.apache.hadoop.hbase.CoprocessorEnvironment;
027import org.apache.hadoop.hbase.HBaseInterfaceAudience;
028import org.apache.hadoop.hbase.RawCellBuilder;
029import org.apache.hadoop.hbase.ServerName;
030import org.apache.hadoop.hbase.client.Connection;
031import org.apache.hadoop.hbase.client.RegionInfo;
032import org.apache.hadoop.hbase.metrics.MetricRegistry;
033import org.apache.hadoop.hbase.regionserver.OnlineRegions;
034import org.apache.hadoop.hbase.regionserver.Region;
035import org.apache.yetus.audience.InterfaceAudience;
036import org.apache.yetus.audience.InterfaceStability;
037
038@InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC)
039@InterfaceStability.Evolving
040public interface RegionCoprocessorEnvironment extends CoprocessorEnvironment<RegionCoprocessor> {
041  /** @return the region associated with this coprocessor */
042  Region getRegion();
043
044  /** @return region information for the region this coprocessor is running on */
045  RegionInfo getRegionInfo();
046
047  /**
048   * @return Interface to Map of regions online on this RegionServer {@link #getServerName()}}.
049   */
050  OnlineRegions getOnlineRegions();
051
052  /** @return shared data between all instances of this coprocessor */
053  ConcurrentMap<String, Object> getSharedData();
054
055  /**
056   * @return Hosting Server's ServerName
057   */
058  ServerName getServerName();
059
060  /**
061   * Returns the hosts' Connection to the Cluster. <b>Do not close! This is a shared connection
062   * with the hosting server. Throws {@link UnsupportedOperationException} if you try to close
063   * or abort it</b>.
064   *
065   * For light-weight usage only. Heavy-duty usage will pull down
066   * the hosting RegionServer responsiveness as well as that of other Coprocessors making use of
067   * this Connection. Use to create table on start or to do administrative operations. Coprocessors
068   * should create their own Connections if heavy usage to avoid impinging on hosting Server
069   * operation. To create a Connection or if a Coprocessor requires a region with a particular
070   * Configuration, use {@link org.apache.hadoop.hbase.client.ConnectionFactory} or
071   * {@link #createConnection(Configuration)}}.
072   *
073   * <p>Be aware that operations that make use of this Connection are executed as the RegionServer
074   * User, the hbase super user that started this server process. Exercise caution running
075   * operations as this User (See {@link #createConnection(Configuration)}} to run as other than
076   * the RegionServer User).
077   *
078   * <p>Be careful RPC'ing from a Coprocessor context. RPC's will fail, stall, retry, and/or crawl
079   * because the remote side is not online, is struggling or it is on the other side of a network
080   * partition. Any use of Connection from inside a Coprocessor must be able to handle all such
081   * hiccups.
082   *
083   * @see #createConnection(Configuration)
084   * @return The host's Connection to the Cluster.
085   */
086  Connection getConnection();
087
088  /**
089   * Creates a cluster connection using the passed Configuration.
090   *
091   * Creating a Connection is a heavy-weight operation. The resultant Connection's cache of
092   * region locations will be empty. Therefore you should cache and reuse Connections rather than
093   * create a Connection on demand. Create on start of your Coprocessor. You will have to cast
094   * the CoprocessorEnvironment appropriately to get at this API at start time because
095   * Coprocessor start method is passed a subclass of this CoprocessorEnvironment or fetch
096   * Connection using a synchronized accessor initializing the Connection on first access. Close
097   * the returned Connection when done to free resources. Using this API rather
098   * than {@link org.apache.hadoop.hbase.client.ConnectionFactory#createConnection(Configuration)}
099   * returns a Connection that will short-circuit RPC if the target is a local resource. Use
100   * ConnectionFactory if you don't need this ability.
101   *
102   * <p>Be careful RPC'ing from a Coprocessor context. RPC's will fail, stall, retry, and/or crawl
103   * because the remote side is not online, is struggling or it is on the other side of a network
104   * partition. Any use of Connection from inside a Coprocessor must be able to handle all such
105   * hiccups.
106   * @return Connection created using the passed conf.
107   */
108  Connection createConnection(Configuration conf) throws IOException;
109
110  /**
111   * Returns a MetricRegistry that can be used to track metrics at the region server level. All
112   * metrics tracked at this level will be shared by all the coprocessor instances
113   * of the same class in the same region server process. Note that there will be one
114   * region coprocessor environment per region in the server, but all of these instances will share
115   * the same MetricRegistry. The metric instances (like Counter, Timer, etc) will also be shared
116   * among all of the region coprocessor instances.
117   *
118   * <p>See ExampleRegionObserverWithMetrics class in the hbase-examples modules to see examples of how
119   * metrics can be instantiated and used.</p>
120   * @return A MetricRegistry for the coprocessor class to track and export metrics.
121   */
122  // Note: we are not exposing getMetricRegistryForRegion(). per-region metrics are already costly
123  // so we do not want to allow coprocessors to export metrics at the region level. We can allow
124  // getMetricRegistryForTable() to allow coprocessors to track metrics per-table, per-regionserver.
125  MetricRegistry getMetricRegistryForRegionServer();
126
127  /**
128   * Returns a CellBuilder so that coprocessors can build cells. These cells can also include tags.
129   * Note that this builder does not support updating seqId of the cells
130   * @return the RawCellBuilder
131   */
132  RawCellBuilder getCellBuilder();
133}