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| # 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.""" | |
| from abc import ABC | |
| import collections | |
| import enum | |
| import functools | |
| import logging | |
| _LOGGER = logging.getLogger(__name__) | |
| class Outcome(ABC): | |
| """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. | |
| """ | |
| 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 | |
| _LOGGER.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. | |
| """ | |
| 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) | |