Step 2: Test connectivity to the ledger

Important

End of support notice: Existing customers will be able to use Amazon QLDB until end of support on 07/31/2025. For more details, see Migrate an Amazon QLDB Ledger to Amazon Aurora PostgreSQL.

In this step, you verify that you can connect to the vehicle-registration ledger in Amazon QLDB using the transactional data API endpoint.

To test connectivity to the ledger

1. Use the following program (connect_to_ledger.py) to create a data session connection to the vehicle-registration ledger.

   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 <https://boto3.amazonaws.com/v1/documentation/api/latest/reference/core/session.html#boto3.session.Session.client>`.
       """
       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()

   Note

   • To run data transactions on your ledger, you must create a QLDB driver object to connect to a specific ledger. This is a different client object than the qldb_client object that you used in the previous step to create the ledger. That previous client is only used to run the management API operations listed in the Amazon QLDB API reference.

   • You must specify a ledger name when you create this driver object.

   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 <https://boto3.amazonaws.com/v1/documentation/api/latest/reference/core/session.html#boto3.session.Session.client>`.
       """
       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.')

   Note

   • To run data transactions on your ledger, you must create a QLDB driver object to connect to a specific ledger. This is a different client object than the qldb_client object that you used in the previous step to create the ledger. That previous client is only used to run the management API operations listed in the Amazon QLDB API reference.

   • First, create a pooled QLDB driver object. You must specify a ledger name when you create this driver.

   • Then, you can create sessions from this pooled driver object.

2. To run the program, enter the following command.

   python connect_to_ledger.py

To create tables in the vehicle-registration ledger, proceed to Step 3: Create tables, indexes, and sample data.