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.client.example;
019
020import java.io.IOException;
021import java.util.ArrayList;
022import java.util.List;
023import java.util.concurrent.Callable;
024import java.util.concurrent.ExecutorService;
025import java.util.concurrent.Executors;
026import java.util.concurrent.ForkJoinPool;
027import java.util.concurrent.Future;
028import java.util.concurrent.ThreadFactory;
029import java.util.concurrent.ThreadLocalRandom;
030import java.util.concurrent.TimeUnit;
031import org.apache.hadoop.conf.Configured;
032import org.apache.hadoop.hbase.Cell;
033import org.apache.hadoop.hbase.CellBuilderFactory;
034import org.apache.hadoop.hbase.CellBuilderType;
035import org.apache.hadoop.hbase.TableName;
036import org.apache.hadoop.hbase.client.Connection;
037import org.apache.hadoop.hbase.client.ConnectionFactory;
038import org.apache.hadoop.hbase.client.Put;
039import org.apache.hadoop.hbase.client.RegionLocator;
040import org.apache.hadoop.hbase.client.Result;
041import org.apache.hadoop.hbase.client.ResultScanner;
042import org.apache.hadoop.hbase.client.Scan;
043import org.apache.hadoop.hbase.client.Table;
044import org.apache.hadoop.hbase.filter.KeyOnlyFilter;
045import org.apache.hadoop.hbase.util.Bytes;
046import org.apache.hadoop.util.Tool;
047import org.apache.hadoop.util.ToolRunner;
048import org.apache.yetus.audience.InterfaceAudience;
049import org.slf4j.Logger;
050import org.slf4j.LoggerFactory;
051
052import org.apache.hbase.thirdparty.com.google.common.util.concurrent.ThreadFactoryBuilder;
053
054/**
055 * Example on how to use HBase's {@link Connection} and {@link Table} in a multi-threaded
056 * environment. Each table is a light weight object that is created and thrown away. Connections are
057 * heavy weight objects that hold on to zookeeper connections, async processes, and other state.
058 *
059 * <pre>
060 * Usage:
061 * bin/hbase org.apache.hadoop.hbase.client.example.MultiThreadedClientExample testTableName 500000
062 * </pre>
063 * <p>
064 * The table should already be created before running the command. This example expects one column
065 * family named d.
066 * </p>
067 * <p>
068 * This is meant to show different operations that are likely to be done in a real world
069 * application. These operations are:
070 * </p>
071 * <ul>
072 * <li>30% of all operations performed are batch writes. 30 puts are created and sent out at a time.
073 * The response for all puts is waited on.</li>
074 * <li>20% of all operations are single writes. A single put is sent out and the response is waited
075 * for.</li>
076 * <li>50% of all operations are scans. These scans start at a random place and scan up to 100 rows.
077 * </li>
078 * </ul>
079 */
080@InterfaceAudience.Private
081public class MultiThreadedClientExample extends Configured implements Tool {
082  private static final Logger LOG = LoggerFactory.getLogger(MultiThreadedClientExample.class);
083  private static final int DEFAULT_NUM_OPERATIONS = 500000;
084
085  /**
086   * The name of the column family. d for default.
087   */
088  private static final byte[] FAMILY = Bytes.toBytes("d");
089
090  /**
091   * For the example we're just using one qualifier.
092   */
093  private static final byte[] QUAL = Bytes.toBytes("test");
094
095  private final ExecutorService internalPool;
096
097  private final int threads;
098
099  public MultiThreadedClientExample() throws IOException {
100    // Base number of threads.
101    // This represents the number of threads you application has
102    // that can be interacting with an hbase client.
103    this.threads = Runtime.getRuntime().availableProcessors() * 4;
104
105    // Daemon threads are great for things that get shut down.
106    ThreadFactory threadFactory =
107      new ThreadFactoryBuilder().setDaemon(true).setNameFormat("internal-pol-%d").build();
108
109    this.internalPool = Executors.newFixedThreadPool(threads, threadFactory);
110  }
111
112  @Override
113  public int run(String[] args) throws Exception {
114
115    if (args.length < 1 || args.length > 2) {
116      System.out.println("Usage: " + this.getClass().getName() + " tableName [num_operations]");
117      return -1;
118    }
119
120    final TableName tableName = TableName.valueOf(args[0]);
121    int numOperations = DEFAULT_NUM_OPERATIONS;
122
123    // the second arg is the number of operations to send.
124    if (args.length == 2) {
125      numOperations = Integer.parseInt(args[1]);
126    }
127
128    // Threads for the client only.
129    //
130    // We don't want to mix hbase and business logic.
131    //
132    ExecutorService service = new ForkJoinPool(threads * 2);
133
134    // Create two different connections showing how it's possible to
135    // separate different types of requests onto different connections
136    final Connection writeConnection = ConnectionFactory.createConnection(getConf(), service);
137    final Connection readConnection = ConnectionFactory.createConnection(getConf(), service);
138
139    // At this point the entire cache for the region locations is full.
140    // Only do this if the number of regions in a table is easy to fit into memory.
141    //
142    // If you are interacting with more than 25k regions on a client then it's probably not good
143    // to do this at all.
144    warmUpConnectionCache(readConnection, tableName);
145    warmUpConnectionCache(writeConnection, tableName);
146
147    List<Future<Boolean>> futures = new ArrayList<>(numOperations);
148    for (int i = 0; i < numOperations; i++) {
149      double r = ThreadLocalRandom.current().nextDouble();
150      Future<Boolean> f;
151
152      // For the sake of generating some synthetic load this queues
153      // some different callables.
154      // These callables are meant to represent real work done by your application.
155      if (r < .30) {
156        f = internalPool.submit(new WriteExampleCallable(writeConnection, tableName));
157      } else if (r < .50) {
158        f = internalPool.submit(new SingleWriteExampleCallable(writeConnection, tableName));
159      } else {
160        f = internalPool.submit(new ReadExampleCallable(writeConnection, tableName));
161      }
162      futures.add(f);
163    }
164
165    // Wait a long time for all the reads/writes to complete
166    for (Future<Boolean> f : futures) {
167      f.get(10, TimeUnit.MINUTES);
168    }
169
170    // Clean up after our selves for cleanliness
171    internalPool.shutdownNow();
172    service.shutdownNow();
173    return 0;
174  }
175
176  private void warmUpConnectionCache(Connection connection, TableName tn) throws IOException {
177    try (RegionLocator locator = connection.getRegionLocator(tn)) {
178      LOG.info("Warmed up region location cache for " + tn + " got "
179        + locator.getAllRegionLocations().size());
180    }
181  }
182
183  /**
184   * Class that will show how to send batches of puts at the same time.
185   */
186  public static class WriteExampleCallable implements Callable<Boolean> {
187    private final Connection connection;
188    private final TableName tableName;
189
190    public WriteExampleCallable(Connection connection, TableName tableName) {
191      this.connection = connection;
192      this.tableName = tableName;
193    }
194
195    @Override
196    public Boolean call() throws Exception {
197
198      // Table implements Closable so we use the try with resource structure here.
199      // https://docs.oracle.com/javase/tutorial/essential/exceptions/tryResourceClose.html
200      try (Table t = connection.getTable(tableName)) {
201        byte[] value = Bytes.toBytes(Double.toString(ThreadLocalRandom.current().nextDouble()));
202        int rows = 30;
203
204        // Array to put the batch
205        ArrayList<Put> puts = new ArrayList<>(rows);
206        for (int i = 0; i < 30; i++) {
207          byte[] rk = Bytes.toBytes(ThreadLocalRandom.current().nextLong());
208          Put p = new Put(rk);
209          p.add(CellBuilderFactory.create(CellBuilderType.SHALLOW_COPY).setRow(rk).setFamily(FAMILY)
210            .setQualifier(QUAL).setTimestamp(p.getTimestamp()).setType(Cell.Type.Put)
211            .setValue(value).build());
212          puts.add(p);
213        }
214
215        // now that we've assembled the batch it's time to push it to hbase.
216        t.put(puts);
217      }
218      return true;
219    }
220  }
221
222  /**
223   * Class to show how to send a single put.
224   */
225  public static class SingleWriteExampleCallable implements Callable<Boolean> {
226    private final Connection connection;
227    private final TableName tableName;
228
229    public SingleWriteExampleCallable(Connection connection, TableName tableName) {
230      this.connection = connection;
231      this.tableName = tableName;
232    }
233
234    @Override
235    public Boolean call() throws Exception {
236      try (Table t = connection.getTable(tableName)) {
237
238        byte[] value = Bytes.toBytes(Double.toString(ThreadLocalRandom.current().nextDouble()));
239        byte[] rk = Bytes.toBytes(ThreadLocalRandom.current().nextLong());
240        Put p = new Put(rk);
241        p.add(CellBuilderFactory.create(CellBuilderType.SHALLOW_COPY).setRow(rk).setFamily(FAMILY)
242          .setQualifier(QUAL).setTimestamp(p.getTimestamp()).setType(Cell.Type.Put).setValue(value)
243          .build());
244        t.put(p);
245      }
246      return true;
247    }
248  }
249
250  /**
251   * Class to show how to scan some rows starting at a random location.
252   */
253  public static class ReadExampleCallable implements Callable<Boolean> {
254    private final Connection connection;
255    private final TableName tableName;
256
257    public ReadExampleCallable(Connection connection, TableName tableName) {
258      this.connection = connection;
259      this.tableName = tableName;
260    }
261
262    @Override
263    public Boolean call() throws Exception {
264
265      // total length in bytes of all read rows.
266      int result = 0;
267
268      // Number of rows the scan will read before being considered done.
269      int toRead = 100;
270      try (Table t = connection.getTable(tableName)) {
271        byte[] rk = Bytes.toBytes(ThreadLocalRandom.current().nextLong());
272        Scan s = new Scan().withStartRow(rk);
273
274        // This filter will keep the values from being sent accross the wire.
275        // This is good for counting or other scans that are checking for
276        // existence and don't rely on the value.
277        s.setFilter(new KeyOnlyFilter());
278
279        // Don't go back to the server for every single row.
280        // We know these rows are small. So ask for 20 at a time.
281        // This would be application specific.
282        //
283        // The goal is to reduce round trips but asking for too
284        // many rows can lead to GC problems on client and server sides.
285        s.setCaching(20);
286
287        // Don't use the cache. While this is a silly test program it's still good to be
288        // explicit that scans normally don't use the block cache.
289        s.setCacheBlocks(false);
290
291        // Open up the scanner and close it automatically when done.
292        try (ResultScanner rs = t.getScanner(s)) {
293
294          // Now go through rows.
295          for (Result r : rs) {
296            // Keep track of things size to simulate doing some real work.
297            result += r.getRow().length;
298            toRead -= 1;
299
300            // Most online applications won't be
301            // reading the entire table so this break
302            // simulates small to medium size scans,
303            // without needing to know an end row.
304            if (toRead <= 0) {
305              break;
306            }
307          }
308        }
309      }
310      return result > 0;
311    }
312  }
313
314  public static void main(String[] args) throws Exception {
315    ToolRunner.run(new MultiThreadedClientExample(), args);
316  }
317}