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Diffstat (limited to 'google/api_core/future/async_future.py')
-rw-r--r-- | google/api_core/future/async_future.py | 162 |
1 files changed, 162 insertions, 0 deletions
diff --git a/google/api_core/future/async_future.py b/google/api_core/future/async_future.py new file mode 100644 index 0000000..88c183f --- /dev/null +++ b/google/api_core/future/async_future.py @@ -0,0 +1,162 @@ +# Copyright 2020, Google LLC +# +# 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. + +"""AsyncIO implementation of the abstract base Future class.""" + +import asyncio + +from google.api_core import exceptions +from google.api_core import retry +from google.api_core import retry_async +from google.api_core.future import base + + +class _OperationNotComplete(Exception): + """Private exception used for polling via retry.""" + + pass + + +RETRY_PREDICATE = retry.if_exception_type( + _OperationNotComplete, + exceptions.TooManyRequests, + exceptions.InternalServerError, + exceptions.BadGateway, +) +DEFAULT_RETRY = retry_async.AsyncRetry(predicate=RETRY_PREDICATE) + + +class AsyncFuture(base.Future): + """A Future that polls peer service to self-update. + + The :meth:`done` method should be implemented by subclasses. The polling + behavior will repeatedly call ``done`` until it returns True. + + .. note:: + + Privacy here is intended to prevent the final class from + overexposing, not to prevent subclasses from accessing methods. + + Args: + retry (google.api_core.retry.Retry): The retry configuration used + when polling. This can be used to control how often :meth:`done` + is polled. Regardless of the retry's ``deadline``, it will be + overridden by the ``timeout`` argument to :meth:`result`. + """ + + def __init__(self, retry=DEFAULT_RETRY): + super().__init__() + self._retry = retry + self._future = asyncio.get_event_loop().create_future() + self._background_task = None + + async def done(self, retry=DEFAULT_RETRY): + """Checks to see if the operation is complete. + + Args: + retry (google.api_core.retry.Retry): (Optional) How to retry the RPC. + + Returns: + bool: True if the operation is complete, False otherwise. + """ + # pylint: disable=redundant-returns-doc, missing-raises-doc + raise NotImplementedError() + + async def _done_or_raise(self): + """Check if the future is done and raise if it's not.""" + result = await self.done() + if not result: + raise _OperationNotComplete() + + async def running(self): + """True if the operation is currently running.""" + result = await self.done() + return not result + + async def _blocking_poll(self, timeout=None): + """Poll and await for the Future to be resolved. + + Args: + timeout (int): + How long (in seconds) to wait for the operation to complete. + If None, wait indefinitely. + """ + if self._future.done(): + return + + retry_ = self._retry.with_deadline(timeout) + + try: + await retry_(self._done_or_raise)() + except exceptions.RetryError: + raise asyncio.TimeoutError( + "Operation did not complete within the designated " "timeout." + ) + + async def result(self, timeout=None): + """Get the result of the operation. + + Args: + timeout (int): + How long (in seconds) to wait for the operation to complete. + If None, wait indefinitely. + + Returns: + google.protobuf.Message: The Operation's result. + + Raises: + google.api_core.GoogleAPICallError: If the operation errors or if + the timeout is reached before the operation completes. + """ + await self._blocking_poll(timeout=timeout) + return self._future.result() + + async def exception(self, timeout=None): + """Get the exception from the operation. + + Args: + timeout (int): How long to wait for the operation to complete. + If None, wait indefinitely. + + Returns: + Optional[google.api_core.GoogleAPICallError]: The operation's + error. + """ + await self._blocking_poll(timeout=timeout) + return self._future.exception() + + def add_done_callback(self, fn): + """Add a callback to be executed when the operation is complete. + + If the operation is completed, the callback will be scheduled onto the + event loop. Otherwise, the callback will be stored and invoked when the + future is done. + + Args: + fn (Callable[Future]): The callback to execute when the operation + is complete. + """ + if self._background_task is None: + self._background_task = asyncio.get_event_loop().create_task( + self._blocking_poll() + ) + self._future.add_done_callback(fn) + + def set_result(self, result): + """Set the Future's result.""" + self._future.set_result(result) + + def set_exception(self, exception): + """Set the Future's exception.""" + self._future.set_exception(exception) |