/**
*
* 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.
*/
package org.apache.hadoop.hbase.client.example;
import com.google.common.util.concurrent.ThreadFactoryBuilder;
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;
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;
/**
* 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);
}
}