| # Copyright 2015 gRPC authors. |
| # |
| # 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, |
| # 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. |
| """Utilities for working with callables.""" |
| |
| import abc |
| import collections |
| import enum |
| import functools |
| import logging |
| |
| import six |
| |
| |
| class Outcome(six.with_metaclass(abc.ABCMeta)): |
| """A sum type describing the outcome of some call. |
| |
| Attributes: |
| kind: One of Kind.RETURNED or Kind.RAISED respectively indicating that the |
| call returned a value or raised an exception. |
| return_value: The value returned by the call. Must be present if kind is |
| Kind.RETURNED. |
| exception: The exception raised by the call. Must be present if kind is |
| Kind.RAISED. |
| """ |
| |
| @enum.unique |
| class Kind(enum.Enum): |
| """Identifies the general kind of the outcome of some call.""" |
| |
| RETURNED = object() |
| RAISED = object() |
| |
| |
| class _EasyOutcome( |
| collections.namedtuple('_EasyOutcome', |
| ['kind', 'return_value', 'exception']), Outcome): |
| """A trivial implementation of Outcome.""" |
| |
| |
| def _call_logging_exceptions(behavior, message, *args, **kwargs): |
| try: |
| return _EasyOutcome(Outcome.Kind.RETURNED, |
| behavior(*args, **kwargs), None) |
| except Exception as e: # pylint: disable=broad-except |
| logging.exception(message) |
| return _EasyOutcome(Outcome.Kind.RAISED, None, e) |
| |
| |
| def with_exceptions_logged(behavior, message): |
| """Wraps a callable in a try-except that logs any exceptions it raises. |
| |
| Args: |
| behavior: Any callable. |
| message: A string to log if the behavior raises an exception. |
| |
| Returns: |
| A callable that when executed invokes the given behavior. The returned |
| callable takes the same arguments as the given behavior but returns a |
| future.Outcome describing whether the given behavior returned a value or |
| raised an exception. |
| """ |
| |
| @functools.wraps(behavior) |
| def wrapped_behavior(*args, **kwargs): |
| return _call_logging_exceptions(behavior, message, *args, **kwargs) |
| |
| return wrapped_behavior |
| |
| |
| def call_logging_exceptions(behavior, message, *args, **kwargs): |
| """Calls a behavior in a try-except that logs any exceptions it raises. |
| |
| Args: |
| behavior: Any callable. |
| message: A string to log if the behavior raises an exception. |
| *args: Positional arguments to pass to the given behavior. |
| **kwargs: Keyword arguments to pass to the given behavior. |
| |
| Returns: |
| An Outcome describing whether the given behavior returned a value or raised |
| an exception. |
| """ |
| return _call_logging_exceptions(behavior, message, *args, **kwargs) |