Python

Source code for gcloud.datastore._implicit_environ

# Copyright 2014 Google Inc. 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.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
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# See the License for the specific language governing permissions and
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"""Module to provide implicit behavior based on enviroment.

Allows the datastore package to infer the current dataset ID and
connection from the enviroment.
"""

import os

from gcloud._helpers import _app_engine_id
from gcloud._helpers import _compute_engine_id
from gcloud._helpers import _lazy_property_deco
from gcloud.datastore.connection import Connection


_DATASET_ENV_VAR_NAME = 'GCLOUD_DATASET_ID'
_GCD_DATASET_ENV_VAR_NAME = 'DATASTORE_DATASET'


def _get_production_dataset_id():
    """Gets the production application ID if it can be inferred."""
    return os.getenv(_DATASET_ENV_VAR_NAME)


def _get_gcd_dataset_id():
    """Gets the GCD application ID if it can be inferred."""
    return os.getenv(_GCD_DATASET_ENV_VAR_NAME)


def _determine_default_dataset_id(dataset_id=None):
    """Determine default dataset ID explicitly or implicitly as fall-back.

    In implicit case, supports four environments. In order of precedence, the
    implicit environments are:

    * GCLOUD_DATASET_ID environment variable
    * DATASTORE_DATASET environment variable (for ``gcd`` testing)
    * Google App Engine application ID
    * Google Compute Engine project ID (from metadata server)

    :type dataset_id: string
    :param dataset_id: Optional. The dataset ID to use as default.

    :rtype: string or ``NoneType``
    :returns: Default dataset ID if it can be determined.
    """
    if dataset_id is None:
        dataset_id = _get_production_dataset_id()

    if dataset_id is None:
        dataset_id = _get_gcd_dataset_id()

    if dataset_id is None:
        dataset_id = _app_engine_id()

    if dataset_id is None:
        dataset_id = _compute_engine_id()

    return dataset_id


[docs]def set_default_dataset_id(dataset_id=None):
    """Set default dataset ID either explicitly or implicitly as fall-back.

    In implicit case, supports four environments. In order of precedence, the
    implicit environments are:

    * GCLOUD_DATASET_ID environment variable
    * DATASTORE_DATASET environment variable (for ``gcd`` testing)
    * Google App Engine application ID
    * Google Compute Engine project ID (from metadata server)

    :type dataset_id: string
    :param dataset_id: Optional. The dataset ID to use as default.

    :raises: :class:`EnvironmentError` if no dataset ID was implied.
    """
    dataset_id = _determine_default_dataset_id(dataset_id=dataset_id)
    if dataset_id is not None:
        _DEFAULTS.dataset_id = dataset_id
    else:
        raise EnvironmentError('No dataset ID could be inferred.')


[docs]def get_default_dataset_id():
    """Get default dataset ID.

    :rtype: string or ``NoneType``
    :returns: The default dataset ID if one has been set.
    """
    return _DEFAULTS.dataset_id


[docs]def get_connection():
    """Shortcut method to establish a connection to the Cloud Datastore.

    Use this if you are going to access several datasets
    with the same set of credentials (unlikely):

    >>> from gcloud import datastore

    >>> connection = datastore.get_connection()
    >>> key1 = datastore.Key('Kind', 1234, dataset_id='dataset1')
    >>> key2 = datastore.Key('Kind', 1234, dataset_id='dataset2')
    >>> entity1 = datastore.get(key1, connection=connection)
    >>> entity2 = datastore.get(key2, connection=connection)

    :rtype: :class:`gcloud.datastore.connection.Connection`
    :returns: A connection defined with the proper credentials.
    """
    return Connection.from_environment()


[docs]def set_default_connection(connection=None):
    """Set default connection either explicitly or implicitly as fall-back.

    :type connection: :class:`gcloud.datastore.connection.Connection`
    :param connection: A connection provided to be the default.
    """
    connection = connection or get_connection()
    _DEFAULTS.connection = connection


[docs]def get_default_connection():
    """Get default connection.

    :rtype: :class:`gcloud.datastore.connection.Connection` or ``NoneType``
    :returns: The default connection if one has been set.
    """
    return _DEFAULTS.connection


class _DefaultsContainer(object):
    """Container for defaults.

    :type connection: :class:`gcloud.datastore.connection.Connection`
    :param connection: Persistent implied connection from environment.

    :type dataset_id: string
    :param dataset_id: Persistent implied dataset ID from environment.
    """

    @_lazy_property_deco
    @staticmethod
    def dataset_id():
        """Return the implicit default dataset ID."""
        return _determine_default_dataset_id()

    @_lazy_property_deco
    @staticmethod
    def connection():
        """Return the implicit default connection.."""
        return get_connection()

    def __init__(self, connection=None, dataset_id=None, implicit=False):
        if connection is not None or not implicit:
            self.connection = connection
        if dataset_id is not None or not implicit:
            self.dataset_id = dataset_id


_DEFAULTS = _DefaultsContainer(implicit=True)