airflow session 源码
airflow session 代码
文件路径：/airflow/utils/session.py
# 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.
from __future__ import annotations
import contextlib
from functools import wraps
from inspect import signature
from typing import Callable, Generator, TypeVar, cast
from airflow import settings
from airflow.typing_compat import ParamSpec
@contextlib.contextmanager
def create_session() -> Generator[settings.SASession, None, None]:
"""Contextmanager that will create and teardown a session."""
if not settings.Session:
raise RuntimeError("Session must be set before!")
session = settings.Session()
try:
yield session
session.commit()
except Exception:
session.rollback()
raise
finally:
session.close()
PS = ParamSpec("PS")
RT = TypeVar("RT")
def find_session_idx(func: Callable[PS, RT]) -> int:
"""Find session index in function call parameter."""
func_params = signature(func).parameters
try:
# func_params is an ordered dict -- this is the "recommended" way of getting the position
session_args_idx = tuple(func_params).index("session")
except ValueError:
raise ValueError(f"Function {func.__qualname__} has no `session` argument") from None
return session_args_idx
def provide_session(func: Callable[PS, RT]) -> Callable[PS, RT]:
"""
Function decorator that provides a session if it isn't provided.
If you want to reuse a session or run the function as part of a
database transaction, you pass it to the function, if not this wrapper
will create one and close it for you.
"""
session_args_idx = find_session_idx(func)
@wraps(func)
def wrapper(*args, **kwargs) -> RT:
if "session" in kwargs or session_args_idx < len(args):
return func(*args, **kwargs)
else:
with create_session() as session:
return func(*args, session=session, **kwargs)
return wrapper
# A fake session to use in functions decorated by provide_session. This allows
# the 'session' argument to be of type Session instead of Optional[Session],
# making it easier to type hint the function body without dealing with the None
# case that can never happen at runtime.
NEW_SESSION: settings.SASession = cast(settings.SASession, None)
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