hbase waitForMaximumCurrentTasks waiting for some tasks to finish

HBase中的waitForMaximumCurrentTasks：等待任务完成的最大限制

在HBase中，有一个名为waitForMaximumCurrentTasks的方法，它用来等待当前正在执行的任务达到最大限制。当需要执行大量任务时，有时候需要等待一部分任务完成后再继续执行新的任务，这时就可以使用这个方法。

什么是waitForMaximumCurrentTasks？

waitForMaximumCurrentTasks是HBase中的一个方法，它的作用是等待当前正在执行的任务达到最大限制。在并发执行任务时，有时候需要控制同时执行的任务数量，以避免资源耗尽或性能下降。这个方法可以帮助我们实现这种限制。

为什么要使用waitForMaximumCurrentTasks？

在实际的开发中，可能会遇到需要控制并发任务数量的情况。例如，当我们需要批量处理大量数据时，为了避免一次性处理太多数据导致系统负载过高，我们可以通过设置最大并发任务数量来控制。这样就能够提高系统的稳定性和性能。

如何使用waitForMaximumCurrentTasks？

下面是一个简单的示例代码，演示了如何使用waitForMaximumCurrentTasks方法来等待并发任务达到最大限制：

import org.apache.hadoop.hbase.client.AsyncConnection;
import org.apache.hadoop.hbase.client.AsyncTable;
import org.apache.hadoop.hbase.client.Connection;
import org.apache.hadoop.hbase.client.ConnectionFactory;
import org.apache.hadoop.hbase.TableName;
import org.apache.hadoop.hbase.client.TableDescriptor;
import org.apache.hadoop.hbase.client.TableDescriptorBuilder;
import org.apache.hadoop.hbase.TableExistsException;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.hbase.HBaseConfiguration;

public class WaitForMaximumCurrentTasksExample {

    public static void main(String[] args) {
        Configuration config = HBaseConfiguration.create();
        try (Connection connection = ConnectionFactory.createConnection(config)) {
            AsyncConnection asyncConnection = ConnectionFactory.createAsyncConnection(config).get();
            TableName tableName = TableName.valueOf("test_table");

            TableDescriptor tableDescriptor = TableDescriptorBuilder.newBuilder(tableName).build();

            try {
                connection.getAdmin().createTable(tableDescriptor);
                AsyncTable asyncTable = asyncConnection.getTable(tableName);
                asyncTable.put(null, null);
                asyncTable.put(null, null);
                asyncTable.put(null, null);
                asyncTable.put(null, null);
                asyncTable.put(null, null);

                asyncTable.put(null, null).thenRun(() -> {
                    System.out.println("All tasks completed!");
                }).exceptionally(throwable -> {
                    System.out.println("Error occurred: " + throwable.getMessage());
                    return null;
                });

                asyncTable.put(null, null).thenRun(() -> {
                    System.out.println("All tasks completed!");
                }).exceptionally(throwable -> {
                    System.out.println("Error occurred: " + throwable.getMessage());
                    return null;
                });

                asyncTable.put(null, null).thenRun(() -> {
                    System.out.println("All tasks completed!");
                }).exceptionally(throwable -> {
                    System.out.println("Error occurred: " + throwable.getMessage());
                    return null;
                });

                asyncTable.put(null, null).thenRun(() -> {
                    System.out.println("All tasks completed!");
                }).exceptionally(throwable -> {
                    System.out.println("Error occurred: " + throwable.getMessage());
                    return null;
                });

                asyncTable.put(null, null).thenRun(() -> {
                    System.out.println("All tasks completed!");
                }).exceptionally(throwable -> {
                    System.out.println("Error occurred: " + throwable.getMessage());
                    return null;
                });

                asyncTable.put(null, null).thenRun(() -> {
                    System.out.println("All tasks completed!");
                }).exceptionally(throwable -> {
                    System.out.println("Error occurred: " + throwable.getMessage());
                    return null;
                });

                asyncTable.put(null, null).thenRun(() -> {
                    System.out.println("All tasks completed!");
                }).exceptionally(throwable -> {
                    System.out.println("Error occurred: " + throwable.getMessage());
                    return null;
                });

                asyncTable.put(null, null).thenRun(() -> {
                    System.out.println("All tasks completed!");
                }).exceptionally(throwable -> {
                    System.out.println("Error occurred: " + throwable.getMessage());
                    return null;
                });

                asyncTable.put(null, null).thenRun(() -> {
                    System.out.println("All tasks completed!");
                }).exceptionally(throwable -> {
                    System.out.println("Error occurred: " + throwable.getMessage());
                    return null;
                });

                // 等待所有任务完成
                asyncTable.waitForMaximumCurrentTasks(5);

            } catch (TableExistsException e) {
                System.out.println("Table already exists!");
            }
        } catch (Exception e) {
            e.printStackTrace();
        }