feat: Second batch of AsyncIO integration

* Polling future
* Page iterator
* With unit tests

google/api_core/future/async_future.py

@@ -0,0 +1,157 @@
+# 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)

google/api_core/gapic_v1/__init__.py

@@ -23,4 +23,6 @@
 
 if sys.version_info >= (3, 6):
     from google.api_core.gapic_v1 import config_async  # noqa: F401
+    from google.api_core.gapic_v1 import method_async  # noqa: F401
     __all__.append("config_async")
+    __all__.append("method_async")

google/api_core/operation_async.py

@@ -0,0 +1,217 @@
+# Copyright 2016 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.
+
+"""Futures for long-running operations returned from Google Cloud APIs.
+
+These futures can be used to synchronously wait for the result of a
+long-running operation using :meth:`Operation.result`:
+
+
+.. code-block:: python
+
+    operation = my_api_client.long_running_method()
+    result = operation.result()
+
+Or asynchronously using callbacks and :meth:`Operation.add_done_callback`:
+
+.. code-block:: python
+
+    operation = my_api_client.long_running_method()
+
+    def my_callback(future):
+        result = future.result()
+
+    operation.add_done_callback(my_callback)
+
+"""
+
+import functools
+import threading
+
+from google.api_core import exceptions
+from google.api_core import protobuf_helpers
+from google.api_core.future import async_future
+from google.longrunning import operations_pb2
+from google.rpc import code_pb2
+
+
+class AsyncOperation(async_future.AsyncFuture):
+    """A Future for interacting with a Google API Long-Running Operation.
+
+    Args:
+        operation (google.longrunning.operations_pb2.Operation): The
+            initial operation.
+        refresh (Callable[[], ~.api_core.operation.Operation]): A callable that
+            returns the latest state of the operation.
+        cancel (Callable[[], None]): A callable that tries to cancel
+            the operation.
+        result_type (func:`type`): The protobuf type for the operation's
+            result.
+        metadata_type (func:`type`): The protobuf type for the operation's
+            metadata.
+        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,
+        operation,
+        refresh,
+        cancel,
+        result_type,
+        metadata_type=None,
+        retry=async_future.DEFAULT_RETRY,
+    ):
+        super().__init__(retry=retry)
+        self._operation = operation
+        self._refresh = refresh
+        self._cancel = cancel
+        self._result_type = result_type
+        self._metadata_type = metadata_type
+        self._completion_lock = threading.Lock()
+        # Invoke this in case the operation came back already complete.
+        self._set_result_from_operation()
+
+    @property
+    def operation(self):
+        """google.longrunning.Operation: The current long-running operation."""
+        return self._operation
+
+    @property
+    def metadata(self):
+        """google.protobuf.Message: the current operation metadata."""
+        if not self._operation.HasField("metadata"):
+            return None
+
+        return protobuf_helpers.from_any_pb(
+            self._metadata_type, self._operation.metadata
+        )
+
+    @classmethod
+    def deserialize(cls, payload):
+        """Deserialize a ``google.longrunning.Operation`` protocol buffer.
+
+        Args:
+            payload (bytes): A serialized operation protocol buffer.
+
+        Returns:
+            ~.operations_pb2.Operation: An Operation protobuf object.
+        """
+        return operations_pb2.Operation.FromString(payload)
+
+    def _set_result_from_operation(self):
+        """Set the result or exception from the operation if it is complete."""
+        # This must be done in a lock to prevent the async_future thread
+        # and main thread from both executing the completion logic
+        # at the same time.
+        with self._completion_lock:
+            # If the operation isn't complete or if the result has already been
+            # set, do not call set_result/set_exception again.
+            # Note: self._result_set is set to True in set_result and
+            # set_exception, in case those methods are invoked directly.
+            if not self._operation.done or self._future.done():
+                return
+
+            if self._operation.HasField("response"):
+                response = protobuf_helpers.from_any_pb(
+                    self._result_type, self._operation.response
+                )
+                self.set_result(response)
+            elif self._operation.HasField("error"):
+                exception = exceptions.GoogleAPICallError(
+                    self._operation.error.message,
+                    errors=(self._operation.error,),
+                    response=self._operation,
+                )
+                self.set_exception(exception)
+            else:
+                exception = exceptions.GoogleAPICallError(
+                    "Unexpected state: Long-running operation had neither "
+                    "response nor error set."
+                )
+                self.set_exception(exception)
+
+    async def _refresh_and_update(self, retry=async_future.DEFAULT_RETRY):
+        """Refresh the operation and update the result if needed.
+
+        Args:
+            retry (google.api_core.retry.Retry): (Optional) How to retry the RPC.
+        """
+        # If the currently cached operation is done, no need to make another
+        # RPC as it will not change once done.
+        if not self._operation.done:
+            self._operation = await self._refresh(retry=retry)
+            self._set_result_from_operation()
+
+    async def done(self, retry=async_future.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.
+        """
+        await self._refresh_and_update(retry)
+        return self._operation.done
+
+    async def cancel(self):
+        """Attempt to cancel the operation.
+
+        Returns:
+            bool: True if the cancel RPC was made, False if the operation is
+                already complete.
+        """
+        result = await self.done()
+        if result:
+            return False
+        else:
+            await self._cancel()
+            return True
+
+    async def cancelled(self):
+        """True if the operation was cancelled."""
+        await self._refresh_and_update()
+        return (
+            self._operation.HasField("error")
+            and self._operation.error.code == code_pb2.CANCELLED
+        )
+
+
+def from_gapic(operation, operations_client, result_type, **kwargs):
+    """Create an operation future from a gapic client.
+
+    This interacts with the long-running operations `service`_ (specific
+    to a given API) via a gapic client.
+
+    .. _service: https://github.com/googleapis/googleapis/blob/\
+                 050400df0fdb16f63b63e9dee53819044bffc857/\
+                 google/longrunning/operations.proto#L38
+
+    Args:
+        operation (google.longrunning.operations_pb2.Operation): The operation.
+        operations_client (google.api_core.operations_v1.OperationsClient):
+            The operations client.
+        result_type (:func:`type`): The protobuf result type.
+        kwargs: Keyword args passed into the :class:`Operation` constructor.
+
+    Returns:
+        ~.api_core.operation.Operation: The operation future to track the given
+            operation.
+    """
+    refresh = functools.partial(operations_client.get_operation, operation.name)
+    cancel = functools.partial(operations_client.cancel_operation, operation.name)
+    return AsyncOperation(operation, refresh, cancel, result_type, **kwargs)