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# Etapa 2: Testar a conectividade com o ledger
**Importante**
Aviso de fim do suporte: os clientes existentes poderão usar o Amazon QLDB até o final do suporte em 31/07/2025. Para obter mais detalhes, consulte [Migrar um Amazon QLDB Ledger para o Amazon](https://aws.amazon.com/blogs/database/migrate-an-amazon-qldb-ledger-to-amazon-aurora-postgresql/) Aurora PostgreSQL.
Nesta etapa, você verifica se pode se conectar ao ledger `vehicle-registration` no Amazon QLDB usando o endpoint de API de dados transacionais.
**Para testar a conexão com o ledger**
1. Use o programa a seguir (`connect_to_ledger.py`) para criar uma conexão de sessão de dados com o ledger `vehicle-registration`.
------
#### [ 3.x ]
```
# Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
# SPDX-License-Identifier: MIT-0
#
# Permission is hereby granted, free of charge, to any person obtaining a copy of this
# software and associated documentation files (the "Software"), to deal in the Software
# without restriction, including without limitation the rights to use, copy, modify,
# merge, publish, distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
# INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
# PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
# HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
# OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
# SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
#
# This code expects that you have AWS credentials setup per:
# https://boto3.amazonaws.com/v1/documentation/api/latest/guide/quickstart.html
from logging import basicConfig, getLogger, INFO
from botocore.exceptions import ClientError
from pyqldb.driver.qldb_driver import QldbDriver
from pyqldbsamples.constants import Constants
logger = getLogger(__name__)
basicConfig(level=INFO)
def create_qldb_driver(ledger_name=Constants.LEDGER_NAME, region_name=None, endpoint_url=None, boto3_session=None):
"""
Create a QLDB driver for executing transactions.
:type ledger_name: str
:param ledger_name: The QLDB ledger name.
:type region_name: str
:param region_name: See [1].
:type endpoint_url: str
:param endpoint_url: See [1].
:type boto3_session: :py:class:`boto3.session.Session`
:param boto3_session: The boto3 session to create the client with (see [1]).
:rtype: :py:class:`pyqldb.driver.qldb_driver.QldbDriver`
:return: A QLDB driver object.
[1]: `Boto3 Session.client Reference `.
"""
qldb_driver = QldbDriver(ledger_name=ledger_name, region_name=region_name, endpoint_url=endpoint_url,
boto3_session=boto3_session)
return qldb_driver
def main(ledger_name=Constants.LEDGER_NAME):
"""
Connect to a given ledger using default settings.
"""
try:
with create_qldb_driver(ledger_name) as driver:
logger.info('Listing table names ')
for table in driver.list_tables():
logger.info(table)
except ClientError as ce:
logger.exception('Unable to list tables.')
raise ce
if __name__ == '__main__':
main()
```
**nota**
Para executar transações de dados em seu ledger, você deve criar um objeto de driver QLDB para se conectar a um ledger específico. Esse é um objeto cliente diferente do objeto `qldb_client` que você usou na etapa anterior para criar o ledger. Esse cliente anterior só é usado para executar as operações da API de gerenciamento listadas no [Referência da API do Amazon QLDB](api-reference.md).
Você deve especificar um nome de ledger ao criar esse objeto de driver.
------
#### [ 2.x ]
```
# Copyright 2019 Amazon.com, Inc. or its affiliates. All Rights Reserved.
# SPDX-License-Identifier: MIT-0
#
# Permission is hereby granted, free of charge, to any person obtaining a copy of this
# software and associated documentation files (the "Software"), to deal in the Software
# without restriction, including without limitation the rights to use, copy, modify,
# merge, publish, distribute, sublicense, and/or sell copies of the Software, and to
# permit persons to whom the Software is furnished to do so.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED,
# INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A
# PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
# HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
# OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
# SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
#
# This code expects that you have AWS credentials setup per:
# https://boto3.amazonaws.com/v1/documentation/api/latest/guide/quickstart.html
from logging import basicConfig, getLogger, INFO
from botocore.exceptions import ClientError
from pyqldb.driver.pooled_qldb_driver import PooledQldbDriver
from pyqldbsamples.constants import Constants
logger = getLogger(__name__)
basicConfig(level=INFO)
def create_qldb_driver(ledger_name=Constants.LEDGER_NAME, region_name=None, endpoint_url=None, boto3_session=None):
"""
Create a QLDB driver for creating sessions.
:type ledger_name: str
:param ledger_name: The QLDB ledger name.
:type region_name: str
:param region_name: See [1].
:type endpoint_url: str
:param endpoint_url: See [1].
:type boto3_session: :py:class:`boto3.session.Session`
:param boto3_session: The boto3 session to create the client with (see [1]).
:rtype: :py:class:`pyqldb.driver.pooled_qldb_driver.PooledQldbDriver`
:return: A pooled QLDB driver object.
[1]: `Boto3 Session.client Reference `.
"""
qldb_driver = PooledQldbDriver(ledger_name=ledger_name, region_name=region_name, endpoint_url=endpoint_url,
boto3_session=boto3_session)
return qldb_driver
def create_qldb_session():
"""
Retrieve a QLDB session object.
:rtype: :py:class:`pyqldb.session.pooled_qldb_session.PooledQldbSession`
:return: A pooled QLDB session object.
"""
qldb_session = pooled_qldb_driver.get_session()
return qldb_session
pooled_qldb_driver = create_qldb_driver()
if __name__ == '__main__':
"""
Connect to a session for a given ledger using default settings.
"""
try:
qldb_session = create_qldb_session()
logger.info('Listing table names ')
for table in qldb_session.list_tables():
logger.info(table)
except ClientError:
logger.exception('Unable to create session.')
```
**nota**
Para executar transações de dados em seu ledger, você deve criar um objeto de driver QLDB para se conectar a um ledger específico. Esse é um objeto cliente diferente do objeto `qldb_client` que você usou na etapa anterior para criar o ledger. Esse cliente anterior só é usado para executar as operações da API de gerenciamento listadas no [Referência da API do Amazon QLDB](api-reference.md).
Primeiro, crie um objeto de driver QLDB em pool. Você deve especificar um nome de ledger ao criar esse objeto de driver.
Em seguida, você pode criar sessões a partir desse objeto de driver agrupado.
------
1. Para executar o programa, digite o comando a seguir.
```
python connect_to_ledger.py
```
Para criar tabelas no ledger `vehicle-registration`, vá para [Etapa 3: criar tabelas, índices e dados de amostra](getting-started.python.step-3.md).