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import json
import functools
import httplib2
import google.auth
import google_auth_httplib2
import google.oauth2.service_account
from airflow.exceptions import AirflowException
from airflow.hooks.base_hook import BaseHook
from airflow.utils.log.logging_mixin import LoggingMixin
_DEFAULT_SCOPES = ('https://www.googleapis.com/auth/cloud-platform',)
[docs]class GoogleCloudBaseHook(BaseHook, LoggingMixin):
"""
A base hook for Google cloud-related hooks. Google cloud has a shared REST
API client that is built in the same way no matter which service you use.
This class helps construct and authorize the credentials needed to then
call googleapiclient.discovery.build() to actually discover and build a client
for a Google cloud service.
The class also contains some miscellaneous helper functions.
All hook derived from this base hook use the 'Google Cloud Platform' connection
type. Three ways of authentication are supported:
Default credentials: Only the 'Project Id' is required. You'll need to
have set up default credentials, such as by the
``GOOGLE_APPLICATION_DEFAULT`` environment variable or from the metadata
server on Google Compute Engine.
JSON key file: Specify 'Project Id', 'Keyfile Path' and 'Scope'.
Legacy P12 key files are not supported.
JSON data provided in the UI: Specify 'Keyfile JSON'.
"""
def __init__(self, gcp_conn_id='google_cloud_default', delegate_to=None):
"""
:param gcp_conn_id: The connection ID to use when fetching connection info.
:type gcp_conn_id: string
:param delegate_to: The account to impersonate, if any.
For this to work, the service account making the request must have
domain-wide delegation enabled.
:type delegate_to: string
"""
self.gcp_conn_id = gcp_conn_id
self.delegate_to = delegate_to
self.extras = self.get_connection(self.gcp_conn_id).extra_dejson
def _get_credentials(self):
"""
Returns the Credentials object for Google API
"""
key_path = self._get_field('key_path', False)
keyfile_dict = self._get_field('keyfile_dict', False)
scope = self._get_field('scope', None)
if scope:
scopes = [s.strip() for s in scope.split(',')]
else:
scopes = _DEFAULT_SCOPES
if not key_path and not keyfile_dict:
self.log.info('Getting connection using `google.auth.default()` '
'since no key file is defined for hook.')
credentials, _ = google.auth.default(scopes=scopes)
elif key_path:
# Get credentials from a JSON file.
if key_path.endswith('.json'):
self.log.debug('Getting connection using JSON key file %s' % key_path)
credentials = (
google.oauth2.service_account.Credentials.from_service_account_file(
key_path, scopes=scopes)
)
elif key_path.endswith('.p12'):
raise AirflowException('Legacy P12 key file are not supported, '
'use a JSON key file.')
else:
raise AirflowException('Unrecognised extension for key file.')
else:
# Get credentials from JSON data provided in the UI.
try:
keyfile_dict = json.loads(keyfile_dict)
# Depending on how the JSON was formatted, it may contain
# escaped newlines. Convert those to actual newlines.
keyfile_dict['private_key'] = keyfile_dict['private_key'].replace(
'\\n', '\n')
credentials = (
google.oauth2.service_account.Credentials.from_service_account_info(
keyfile_dict, scopes=scopes)
)
except json.decoder.JSONDecodeError:
raise AirflowException('Invalid key JSON.')
return credentials.with_subject(self.delegate_to) \
if self.delegate_to else credentials
def _get_access_token(self):
"""
Returns a valid access token from Google API Credentials
"""
return self._get_credentials().token
def _authorize(self):
"""
Returns an authorized HTTP object to be used to build a Google cloud
service hook connection.
"""
credentials = self._get_credentials()
http = httplib2.Http()
authed_http = google_auth_httplib2.AuthorizedHttp(
credentials, http=http)
return authed_http
def _get_field(self, f, default=None):
"""
Fetches a field from extras, and returns it. This is some Airflow
magic. The google_cloud_platform hook type adds custom UI elements
to the hook page, which allow admins to specify service_account,
key_path, etc. They get formatted as shown below.
"""
long_f = 'extra__google_cloud_platform__{}'.format(f)
if hasattr(self, 'extras') and long_f in self.extras:
return self.extras[long_f]
else:
return default
@property
def project_id(self):
return self._get_field('project')
[docs] def fallback_to_default_project_id(func):
"""
Decorator that provides fallback for Google Cloud Platform project id. If
the project is None it will be replaced with the project_id from the
service account the Hook is authenticated with. Project id can be specified
either via project_id kwarg or via first parameter in positional args.
:param func: function to wrap
:return: result of the function call
"""
@functools.wraps(func)
def inner_wrapper(self, *args, **kwargs):
if len(args) > 0:
raise AirflowException(
"Use keyword arguments when initializing method with the "
"'fallback_to_default_project_id' decorator")
if 'project_id' in kwargs:
kwargs['project_id'] = self._get_project_id(kwargs['project_id'])
else:
kwargs['project_id'] = self._get_project_id(None)
if not kwargs['project_id']:
raise AirflowException("The project id must be passed either as "
"keyword project_id parameter or as project_id extra "
"in GCP connection definition. Both are not set!")
return func(self, *args, **kwargs)
return inner_wrapper
fallback_to_default_project_id = staticmethod(fallback_to_default_project_id)
def _get_project_id(self, project_id):
"""
In case project_id is None, overrides it with default project_id from
the service account that is authorized.
:param project_id: project id to
:type project_id: str
:return: the project_id specified or default project id if project_id is None
"""
return project_id if project_id else self.project_id