Java tutorial
package learn.jersey.services; import java.io.IOException; import java.util.ArrayList; import java.util.List; import java.util.concurrent.Callable; import java.util.concurrent.ExecutorService; import java.util.concurrent.Executors; import java.util.concurrent.ForkJoinPool; import java.util.concurrent.Future; import java.util.concurrent.ThreadFactory; import java.util.concurrent.ThreadLocalRandom; import java.util.concurrent.TimeUnit; import org.apache.commons.logging.Log; import org.apache.commons.logging.LogFactory; import org.apache.hadoop.conf.Configured; import org.apache.hadoop.hbase.TableName; import org.apache.hadoop.hbase.client.Connection; import org.apache.hadoop.hbase.client.ConnectionFactory; import org.apache.hadoop.hbase.client.Put; import org.apache.hadoop.hbase.client.RegionLocator; import org.apache.hadoop.hbase.client.Result; import org.apache.hadoop.hbase.client.ResultScanner; import org.apache.hadoop.hbase.client.Scan; import org.apache.hadoop.hbase.client.Table; import org.apache.hadoop.hbase.filter.KeyOnlyFilter; import org.apache.hadoop.hbase.util.Bytes; import org.apache.hadoop.util.Tool; import org.apache.hadoop.util.ToolRunner; /** * * 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. */ import com.google.common.util.concurrent.ThreadFactoryBuilder; /** * Example on how to use HBase's {@link Connection} and {@link Table} in a * multi-threaded environment. Each table is a light weight object that is * created and thrown away. Connections are heavy weight objects that hold on to * zookeeper connections, async processes, and other state. * * <pre> * Usage: * bin/hbase org.apache.hadoop.hbase.client.example.MultiThreadedClientExample testTableName 500000 * </pre> * * <p> * The table should already be created before running the command. This example * expects one column family named d. * </p> * <p> * This is meant to show different operations that are likely to be done in a * real world application. These operations are: * </p> * * <ul> * <li>30% of all operations performed are batch writes. 30 puts are created and * sent out at a time. The response for all puts is waited on.</li> * <li>20% of all operations are single writes. A single put is sent out and the * response is waited for.</li> * <li>50% of all operations are scans. These scans start at a random place and * scan up to 100 rows.</li> * </ul> * */ public class MultiThreadedClientExample extends Configured implements Tool { private static final Log LOG = LogFactory.getLog(MultiThreadedClientExample.class); private static final int DEFAULT_NUM_OPERATIONS = 500000; /** * The name of the column family. * * d for default. */ private static final byte[] FAMILY = Bytes.toBytes("d"); /** * For the example we're just using one qualifier. */ private static final byte[] QUAL = Bytes.toBytes("test"); private final ExecutorService internalPool; private final int threads; public MultiThreadedClientExample() throws IOException { // Base number of threads. // This represents the number of threads you application has // that can be interacting with an hbase client. this.threads = Runtime.getRuntime().availableProcessors() * 4; // Daemon threads are great for things that get shut down. ThreadFactory threadFactory = new ThreadFactoryBuilder().setDaemon(true).setNameFormat("internal-pol-%d") .build(); this.internalPool = Executors.newFixedThreadPool(threads, threadFactory); } @Override public int run(String[] args) throws Exception { if (args.length < 1 || args.length > 2) { System.out.println("Usage: " + this.getClass().getName() + " tableName [num_operations]"); return -1; } final TableName tableName = TableName.valueOf(args[0]); int numOperations = DEFAULT_NUM_OPERATIONS; // the second arg is the number of operations to send. if (args.length == 2) { numOperations = Integer.parseInt(args[1]); } // Threads for the client only. // // We don't want to mix hbase and business logic. // ExecutorService service = new ForkJoinPool(threads * 2); // Create two different connections showing how it's possible to // separate different types of requests onto different connections final Connection writeConnection = ConnectionFactory.createConnection(getConf(), service); final Connection readConnection = ConnectionFactory.createConnection(getConf(), service); // At this point the entire cache for the region locations is full. // Only do this if the number of regions in a table is easy to fit into // memory. // // If you are interacting with more than 25k regions on a client then // it's probably not good // to do this at all. warmUpConnectionCache(readConnection, tableName); warmUpConnectionCache(writeConnection, tableName); List<Future<Boolean>> futures = new ArrayList<>(numOperations); for (int i = 0; i < numOperations; i++) { double r = ThreadLocalRandom.current().nextDouble(); Future<Boolean> f; // For the sake of generating some synthetic load this queues // some different callables. // These callables are meant to represent real work done by your // application. if (r < .30) { f = internalPool.submit(new WriteExampleCallable(writeConnection, tableName)); } else if (r < .50) { f = internalPool.submit(new SingleWriteExampleCallable(writeConnection, tableName)); } else { f = internalPool.submit(new ReadExampleCallable(writeConnection, tableName)); } futures.add(f); } // Wait a long time for all the reads/writes to complete for (Future<Boolean> f : futures) { f.get(10, TimeUnit.MINUTES); } // Clean up after our selves for cleanliness internalPool.shutdownNow(); service.shutdownNow(); return 0; } private void warmUpConnectionCache(Connection connection, TableName tn) throws IOException { try (RegionLocator locator = connection.getRegionLocator(tn)) { LOG.info( "Warmed up region location cache for " + tn + " got " + locator.getAllRegionLocations().size()); } } /** * Class that will show how to send batches of puts at the same time. */ public static class WriteExampleCallable implements Callable<Boolean> { private final Connection connection; private final TableName tableName; public WriteExampleCallable(Connection connection, TableName tableName) { this.connection = connection; this.tableName = tableName; } @Override public Boolean call() throws Exception { // Table implements Closable so we use the try with resource // structure here. // https://docs.oracle.com/javase/tutorial/essential/exceptions/tryResourceClose.html try (Table t = connection.getTable(tableName)) { byte[] value = Bytes.toBytes(Double.toString(ThreadLocalRandom.current().nextDouble())); int rows = 30; // Array to put the batch ArrayList<Put> puts = new ArrayList<>(rows); for (int i = 0; i < 30; i++) { byte[] rk = Bytes.toBytes(ThreadLocalRandom.current().nextLong()); Put p = new Put(rk); p.addImmutable(FAMILY, QUAL, value); puts.add(p); } // now that we've assembled the batch it's time to push it to // hbase. t.put(puts); } return true; } } /** * Class to show how to send a single put. */ public static class SingleWriteExampleCallable implements Callable<Boolean> { private final Connection connection; private final TableName tableName; public SingleWriteExampleCallable(Connection connection, TableName tableName) { this.connection = connection; this.tableName = tableName; } @Override public Boolean call() throws Exception { try (Table t = connection.getTable(tableName)) { byte[] value = Bytes.toBytes(Double.toString(ThreadLocalRandom.current().nextDouble())); byte[] rk = Bytes.toBytes(ThreadLocalRandom.current().nextLong()); Put p = new Put(rk); p.addImmutable(FAMILY, QUAL, value); t.put(p); } return true; } } /** * Class to show how to scan some rows starting at a random location. */ public static class ReadExampleCallable implements Callable<Boolean> { private final Connection connection; private final TableName tableName; public ReadExampleCallable(Connection connection, TableName tableName) { this.connection = connection; this.tableName = tableName; } @Override public Boolean call() throws Exception { // total length in bytes of all read rows. int result = 0; // Number of rows the scan will read before being considered done. int toRead = 100; try (Table t = connection.getTable(tableName)) { byte[] rk = Bytes.toBytes(ThreadLocalRandom.current().nextLong()); Scan s = new Scan(rk); // This filter will keep the values from being sent accross the // wire. // This is good for counting or other scans that are checking // for // existence and don't rely on the value. s.setFilter(new KeyOnlyFilter()); // Don't go back to the server for every single row. // We know these rows are small. So ask for 20 at a time. // This would be application specific. // // The goal is to reduce round trips but asking for too // many rows can lead to GC problems on client and server sides. s.setCaching(20); // Don't use the cache. While this is a silly test program it's // still good to be // explicit that scans normally don't use the block cache. s.setCacheBlocks(false); // Open up the scanner and close it automatically when done. try (ResultScanner rs = t.getScanner(s)) { // Now go through rows. for (Result r : rs) { // Keep track of things size to simulate doing some real // work. result += r.getRow().length; toRead -= 1; // Most online applications won't be // reading the entire table so this break // simulates small to medium size scans, // without needing to know an end row. if (toRead <= 0) { break; } } } } return result > 0; } } public static void main(String[] args) throws Exception { ToolRunner.run(new MultiThreadedClientExample(), args); } }