#
# Licensed to the Apache Software Foundation (ASF) under one
# or more contributor license agreements. See the NOTICE file
# distributed with this work for additional information
# regarding copyright ownership. The ASF licenses this file
# to you 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, 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.
import json
import logging
from typing import Any, Optional
from cryptography.fernet import InvalidToken as InvalidFernetToken
from sqlalchemy import Boolean, Column, Integer, String, Text
from sqlalchemy.ext.declarative import declared_attr
from sqlalchemy.orm import Session, reconstructor, synonym
from airflow.configuration import ensure_secrets_loaded
from airflow.models.base import ID_LEN, Base
from airflow.models.crypto import get_fernet
from airflow.secrets.metastore import MetastoreBackend
from airflow.utils.log.logging_mixin import LoggingMixin
from airflow.utils.log.secrets_masker import mask_secret
from airflow.utils.session import provide_session
[docs]log = logging.getLogger(__name__)
[docs]class Variable(Base, LoggingMixin):
"""
Variables are a generic way to store and retrieve arbitrary content or settings
as a simple key value store within Airflow.
"""
[docs] __tablename__ = "variable"
__NO_DEFAULT_SENTINEL = object()
[docs] id = Column(Integer, primary_key=True)
[docs] key = Column(String(ID_LEN), unique=True)
_val = Column('val', Text)
[docs] description = Column(Text)
[docs] is_encrypted = Column(Boolean, unique=False, default=False)
def __init__(self, key=None, val=None, description=None):
super().__init__()
self.key = key
self.val = val
self.description = description
@reconstructor
[docs] def on_db_load(self):
if self._val:
mask_secret(self.val, self.key)
[docs] def __repr__(self):
# Hiding the value
return f'{self.key} : {self._val}'
[docs] def get_val(self):
"""Get Airflow Variable from Metadata DB and decode it using the Fernet Key"""
if self._val is not None and self.is_encrypted:
try:
fernet = get_fernet()
return fernet.decrypt(bytes(self._val, 'utf-8')).decode()
except InvalidFernetToken:
self.log.error("Can't decrypt _val for key=%s, invalid token or value", self.key)
return None
except Exception:
self.log.error("Can't decrypt _val for key=%s, FERNET_KEY configuration missing", self.key)
return None
else:
return self._val
[docs] def set_val(self, value):
"""Encode the specified value with Fernet Key and store it in Variables Table."""
if value is not None:
fernet = get_fernet()
self._val = fernet.encrypt(bytes(value, 'utf-8')).decode()
self.is_encrypted = fernet.is_encrypted
@declared_attr
[docs] def val(cls):
"""Get Airflow Variable from Metadata DB and decode it using the Fernet Key"""
return synonym('_val', descriptor=property(cls.get_val, cls.set_val))
@classmethod
[docs] def setdefault(cls, key, default, description=None, deserialize_json=False):
"""
Like a Python builtin dict object, setdefault returns the current value
for a key, and if it isn't there, stores the default value and returns it.
:param key: Dict key for this Variable
:param default: Default value to set and return if the variable
isn't already in the DB
:param deserialize_json: Store this as a JSON encoded value in the DB
and un-encode it when retrieving a value
:return: Mixed
"""
obj = Variable.get(key, default_var=None, deserialize_json=deserialize_json)
if obj is None:
if default is not None:
Variable.set(key, default, description=description, serialize_json=deserialize_json)
return default
else:
raise ValueError('Default Value must be set')
else:
return obj
@classmethod
[docs] def get(
cls,
key: str,
default_var: Any = __NO_DEFAULT_SENTINEL,
deserialize_json: bool = False,
) -> Any:
"""
Gets a value for an Airflow Variable Key
:param key: Variable Key
:param default_var: Default value of the Variable if the Variable doesn't exist
:param deserialize_json: Deserialize the value to a Python dict
"""
var_val = Variable.get_variable_from_secrets(key=key)
if var_val is None:
if default_var is not cls.__NO_DEFAULT_SENTINEL:
return default_var
else:
raise KeyError(f'Variable {key} does not exist')
else:
if deserialize_json:
obj = json.loads(var_val)
mask_secret(var_val, key)
return obj
else:
mask_secret(var_val, key)
return var_val
@classmethod
@provide_session
[docs] def set(
cls,
key: str,
value: Any,
description: Optional[str] = None,
serialize_json: bool = False,
session: Session = None,
):
"""
Sets a value for an Airflow Variable with a given Key.
This operation will overwrite an existing variable.
:param key: Variable Key
:param value: Value to set for the Variable
:param description: Description of the Variable
:param serialize_json: Serialize the value to a JSON string
:param session: SQL Alchemy Sessions
"""
# check if the secret exists in the custom secrets backend.
cls.check_for_write_conflict(key)
if serialize_json:
stored_value = json.dumps(value, indent=2)
else:
stored_value = str(value)
Variable.delete(key, session=session)
session.add(Variable(key=key, val=stored_value, description=description))
session.flush()
@classmethod
@provide_session
[docs] def update(
cls,
key: str,
value: Any,
serialize_json: bool = False,
session: Session = None,
):
"""
Updates a given Airflow Variable with the Provided value
:param key: Variable Key
:param value: Value to set for the Variable
:param serialize_json: Serialize the value to a JSON string
:param session: SQL Alchemy Session
"""
cls.check_for_write_conflict(key)
if cls.get_variable_from_secrets(key=key) is None:
raise KeyError(f'Variable {key} does not exist')
obj = session.query(cls).filter(cls.key == key).first()
if obj is None:
raise AttributeError(f'Variable {key} does not exist in the Database and cannot be updated.')
cls.set(key, value, description=obj.description, serialize_json=serialize_json)
@classmethod
@provide_session
[docs] def delete(cls, key: str, session: Session = None) -> int:
"""
Delete an Airflow Variable for a given key
:param key: Variable Key
:param session: SQL Alchemy Sessions
"""
return session.query(cls).filter(cls.key == key).delete()
[docs] def rotate_fernet_key(self):
"""Rotate Fernet Key"""
fernet = get_fernet()
if self._val and self.is_encrypted:
self._val = fernet.rotate(self._val.encode('utf-8')).decode()
@staticmethod
[docs] def check_for_write_conflict(key: str) -> None:
"""
Logs a warning if a variable exists outside of the metastore.
If we try to write a variable to the metastore while the same key
exists in an environment variable or custom secrets backend, then
subsequent reads will not read the set value.
:param key: Variable Key
"""
for secrets_backend in ensure_secrets_loaded():
if not isinstance(secrets_backend, MetastoreBackend):
try:
var_val = secrets_backend.get_variable(key=key)
if var_val is not None:
log.warning(
"The variable {key} is defined in the {cls} secrets backend, which takes "
"precedence over reading from the database. The value in the database will be "
"updated, but to read it you have to delete the conflicting variable "
"from {cls}".format(key=key, cls=secrets_backend.__class__.__name__)
)
return
except Exception:
log.exception(
'Unable to retrieve variable from secrets backend (%s). '
'Checking subsequent secrets backend.',
type(secrets_backend).__name__,
)
return None
@staticmethod
[docs] def get_variable_from_secrets(key: str) -> Optional[str]:
"""
Get Airflow Variable by iterating over all Secret Backends.
:param key: Variable Key
:return: Variable Value
"""
for secrets_backend in ensure_secrets_loaded():
try:
var_val = secrets_backend.get_variable(key=key)
if var_val is not None:
return var_val
except Exception:
log.exception(
'Unable to retrieve variable from secrets backend (%s). '
'Checking subsequent secrets backend.',
type(secrets_backend).__name__,
)
return None
