Source code for pyqldb.driver.base_qldb_driver

# Copyright 2019, Inc. or its affiliates. All Rights Reserved.
# Licensed under the Apache License, Version 2.0 (the "License"). You may not use this file except in compliance with
# the License. A copy of the License is located at
# or in the "license" file accompanying this file. This file 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.
from abc import ABC, abstractmethod
from logging import getLogger

from boto3 import client
from botocore.config import Config
from boto3.session import Session

from .. import __version__
from ..communication.session_client import SessionClient
from ..session.qldb_session import QldbSession

logger = getLogger(__name__)
SERVICE_DESCRIPTION = 'QLDB Driver for Python v{}'.format(__version__)
SERVICE_NAME = 'qldb-session'
SERVICE_RETRY = {'max_attempts': 0}

[docs]class BaseQldbDriver(ABC): """ An abstract base class representing a factory for creating sessions. :type ledger_name: str :param ledger_name: The QLDB ledger name. :type retry_limit: int :param retry_limit: The number of automatic retries for statement executions using convenience methods on sessions when an OCC conflict or retriable exception occurs. This value must not be negative. :type read_ahead: int :param read_ahead: The number of read-ahead buffers. Determines the maximum number of statement result pages that can be buffered in memory. This value must be either 0, to disable read-ahead, or a minimum of 2. :type executor: :py:class:`concurrent.futures.thread.ThreadPoolExecutor` :param executor: A specific, optional, executor to be used by the retrieval thread if read-ahead is enabled. :type region_name: str :param region_name: See [1]. :type verify: bool/str :param verify: See [1]. :type endpoint_url: str :param endpoint_url: See [1]. :type aws_access_key_id: str :param aws_access_key_id: See [1]. :type aws_secret_access_key: str :param aws_secret_access_key: See [1]. :type aws_session_token: str :param aws_session_token: See [1]. :type config: :py:class:`botocore.config.Config` :param config: See [2]. Note that parameter user_agent_extra will be overwritten. :type boto3_session: :py:class:`boto3.session.Session` :param boto3_session: The boto3 session to create the client with (see [1]). The boto3 session is expected to be configured correctly. :raises TypeError: When config is not an instance of :py:class:`botocore.config.Config`. When boto3_session is not an instance of :py:class:`boto3.session.Session`. :raises ValueError: When `read_ahead` or `retry_limit` is not set to the allowed values specified. [1]: `Boto3 Session.client Reference <>`_. [2]: `Botocore Config Reference <>`_. """ def __init__(self, ledger_name, retry_limit=4, read_ahead=0, executor=None, region_name=None, verify=None, endpoint_url=None, aws_access_key_id=None, aws_secret_access_key=None, aws_session_token=None, config=None, boto3_session=None): if retry_limit < 0: raise ValueError('Value for retry_limit cannot be negative.') if read_ahead < 2 and read_ahead != 0: raise ValueError('Value for read_ahead must be 0 or 2 or greater.') self._ledger_name = ledger_name self._retry_limit = retry_limit self._read_ahead = read_ahead self._executor = executor self._is_closed = False if config is not None: if not isinstance(config, Config): raise TypeError('config must be of type botocore.config.Config. Found: {}' .format(type(config).__name__)) self._config = config.merge(DEFAULT_CONFIG) else: self._config = DEFAULT_CONFIG if boto3_session is not None: if not isinstance(boto3_session, Session): raise TypeError('boto3_session must be of type boto3.session.Session. Found: {}' .format(type(boto3_session).__name__)) if region_name is not None or aws_access_key_id is not None or aws_secret_access_key is not None or \ aws_session_token is not None: logger.warning('Custom parameters were detected while using a specified Boto3 client and will be ' 'ignored. Please preconfigure the Boto3 client with those parameters instead.') self._client = boto3_session.client(SERVICE_NAME, verify=verify, endpoint_url=endpoint_url, config=self._config) else: self._client = client(SERVICE_NAME, region_name=region_name, verify=verify, endpoint_url=endpoint_url, aws_access_key_id=aws_access_key_id, aws_secret_access_key=aws_secret_access_key, aws_session_token=aws_session_token, config=self._config) def __enter__(self): """ Context Manager function to support the 'with' statement. """ return self def __exit__(self, exc_type, exc_val, exc_tb): """ Context Manager function to support the 'with' statement. """ self.close()
[docs] @abstractmethod def get_session(self): """ Retrieve a QldbSession object. This method must be overridden. """ pass
@property def read_ahead(self): """ The number of read-ahead buffers to be made available per `StreamCursor` instantiated by this driver. Determines the maximum number of result pages that can be buffered in memory. .. seealso:: :py:class:`pyqldb.cursor.stream_cursor.StreamCursor` """ return self._read_ahead @property def retry_limit(self): """ The number of automatic retries for statement executions using convenience methods on sessions when an OCC conflict or retriable exception occurs. """ return self._retry_limit
[docs] def close(self): """ Close this driver. """ self._is_closed = True
def _create_new_session(self): """ Create a new QldbSession object. """ session_client = SessionClient.start_session(self._ledger_name, self._client) return QldbSession(session_client, self._read_ahead, self._retry_limit, self._executor)