示例:通过 HappyBase API 运行 Python 版“Hello World”应用

本示例是一个非常简单的“hello world”应用,采用 Python 编写而成,旨在说明如何实现以下操作:

  • 连接到 Cloud Bigtable 实例。
  • 新建一个表。
  • 将数据写入表中。
  • 重新读取这些数据。
  • 删除表。

运行示例

本示例使用 Python 版 Google Cloud 客户端库HappyBase 软件包HappyBase API 的一种实现)与 Cloud Bigtable 进行通信。如果您需要将现有 HBase 工作负载移至 Cloud Bigtable,请使用 HappyBase 软件包。对于新应用,请参阅使用 Cloud Bigtable 软件包的“hello world”示例

要运行此示例程序,请按照 GitHub 上的示例说明执行操作。

将 HappyBase API 与 Cloud Bigtable 搭配使用

示例应用会连接到 Cloud Bigtable 并演示一些简单操作。

安装和导入客户端库

您可以使用 PIP 将所需的 Python 软件包安装到 virtualenv 环境中。该示例包含一个需求文件,其中定义了所需的软件包。

google-cloud-happybase==0.33.0

然后可以导入模块。

from google.cloud import bigtable
from google.cloud import happybase

连接到 Cloud Bigtable

bigtable.Client 传递到 happybase.Connection 即可连接到 Cloud Bigtable。

# The client must be created with admin=True because it will create a
# table.
client = bigtable.Client(project=project_id, admin=True)
instance = client.instance(instance_id)
connection = happybase.Connection(instance=instance)

创建表

使用 Connection.create_table() 创建表及其列族。

print('Creating the {} table.'.format(table_name))
column_family_name = 'cf1'
connection.create_table(
    table_name,
    {
        column_family_name: dict()  # Use default options.
    })

将行写入表

使用 Connection.table() 获取现有 Table。然后使用 Table.put() 向该表中写入一行。

print('Writing some greetings to the table.')
table = connection.table(table_name)
column_name = '{fam}:greeting'.format(fam=column_family_name)
greetings = [
    'Hello World!',
    'Hello Cloud Bigtable!',
    'Hello HappyBase!',
]

for i, value in enumerate(greetings):
    # Note: This example uses sequential numeric IDs for simplicity,
    # but this can result in poor performance in a production
    # application.  Since rows are stored in sorted order by key,
    # sequential keys can result in poor distribution of operations
    # across nodes.
    #
    # For more information about how to design a Bigtable schema for
    # the best performance, see the documentation:
    #
    #     https://cloud.google.com/bigtable/docs/schema-design
    row_key = 'greeting{}'.format(i)
    table.put(
        row_key, {column_name.encode('utf-8'): value.encode('utf-8')}
    )

按行键读取行

通过 Table.row() 使用行键直接获取行。

print('Getting a single greeting by row key.')
key = 'greeting0'.encode('utf-8')
row = table.row(key)
print('\t{}: {}'.format(key, row[column_name.encode('utf-8')]))

扫描所有表行

使用 Table.scan() 获取一定范围的行。

print('Scanning for all greetings:')

for key, row in table.scan():
    print('\t{}: {}'.format(key, row[column_name.encode('utf-8')]))

删除表

使用 Connection.delete_table() 删除表。

print('Deleting the {} table.'.format(table_name))
connection.delete_table(table_name)

综合应用

以下为不包含注释的完整示例。



"""Demonstrates how to connect to Cloud Bigtable and run some basic operations.

Prerequisites:

- Create a Cloud Bigtable cluster.
  https://cloud.google.com/bigtable/docs/creating-cluster
- Set your Google Application Default Credentials.
  https://developers.google.com/identity/protocols/application-default-credentials
"""

import argparse

from google.cloud import bigtable
from google.cloud import happybase

def main(project_id, instance_id, table_name):
    client = bigtable.Client(project=project_id, admin=True)
    instance = client.instance(instance_id)
    connection = happybase.Connection(instance=instance)

    try:
        print('Creating the {} table.'.format(table_name))
        column_family_name = 'cf1'
        connection.create_table(
            table_name,
            {
                column_family_name: dict()  # Use default options.
            })

        print('Writing some greetings to the table.')
        table = connection.table(table_name)
        column_name = '{fam}:greeting'.format(fam=column_family_name)
        greetings = [
            'Hello World!',
            'Hello Cloud Bigtable!',
            'Hello HappyBase!',
        ]

        for i, value in enumerate(greetings):
            row_key = 'greeting{}'.format(i)
            table.put(
                row_key, {column_name.encode('utf-8'): value.encode('utf-8')}
            )

        print('Getting a single greeting by row key.')
        key = 'greeting0'.encode('utf-8')
        row = table.row(key)
        print('\t{}: {}'.format(key, row[column_name.encode('utf-8')]))

        print('Scanning for all greetings:')

        for key, row in table.scan():
            print('\t{}: {}'.format(key, row[column_name.encode('utf-8')]))

        print('Deleting the {} table.'.format(table_name))
        connection.delete_table(table_name)

    finally:
        connection.close()

if __name__ == '__main__':
    parser = argparse.ArgumentParser(
        description=__doc__,
        formatter_class=argparse.ArgumentDefaultsHelpFormatter)
    parser.add_argument('project_id', help='Your Cloud Platform project ID.')
    parser.add_argument(
        'instance_id', help='ID of the Cloud Bigtable instance to connect to.')
    parser.add_argument(
        '--table',
        help='Table to create and destroy.',
        default='Hello-Bigtable')

    args = parser.parse_args()
    main(args.project_id, args.instance_id, args.table)