1# Copyright 2020, Google LLC
2#
3# Licensed under the Apache License, Version 2.0 (the "License");
4# you may not use this file except in compliance with the License.
5# You may obtain a copy of the License at
6#
7# http://www.apache.org/licenses/LICENSE-2.0
8#
9# Unless required by applicable law or agreed to in writing, software
10# distributed under the License is distributed on an "AS IS" BASIS,
11# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12# See the License for the specific language governing permissions and
13# limitations under the License.
14
15"""AsyncIO implementation of the abstract base Future class."""
16
17import asyncio
18
19from google.api_core import exceptions
20from google.api_core import retry
21from google.api_core import retry_async
22from google.api_core.future import base
23
24
25class _OperationNotComplete(Exception):
26 """Private exception used for polling via retry."""
27
28 pass
29
30
31RETRY_PREDICATE = retry.if_exception_type(
32 _OperationNotComplete,
33 exceptions.TooManyRequests,
34 exceptions.InternalServerError,
35 exceptions.BadGateway,
36)
37DEFAULT_RETRY = retry_async.AsyncRetry(predicate=RETRY_PREDICATE)
38
39
40class AsyncFuture(base.Future):
41 """A Future that polls peer service to self-update.
42
43 The :meth:`done` method should be implemented by subclasses. The polling
44 behavior will repeatedly call ``done`` until it returns True.
45
46 .. note::
47
48 Privacy here is intended to prevent the final class from
49 overexposing, not to prevent subclasses from accessing methods.
50
51 Args:
52 retry (google.api_core.retry.Retry): The retry configuration used
53 when polling. This can be used to control how often :meth:`done`
54 is polled. Regardless of the retry's ``deadline``, it will be
55 overridden by the ``timeout`` argument to :meth:`result`.
56 """
57
58 def __init__(self, retry=DEFAULT_RETRY):
59 super().__init__()
60 self._retry = retry
61 self._future = asyncio.get_event_loop().create_future()
62 self._background_task = None
63
64 async def done(self, retry=DEFAULT_RETRY):
65 """Checks to see if the operation is complete.
66
67 Args:
68 retry (google.api_core.retry.Retry): (Optional) How to retry the RPC.
69
70 Returns:
71 bool: True if the operation is complete, False otherwise.
72 """
73 # pylint: disable=redundant-returns-doc, missing-raises-doc
74 raise NotImplementedError()
75
76 async def _done_or_raise(self):
77 """Check if the future is done and raise if it's not."""
78 result = await self.done()
79 if not result:
80 raise _OperationNotComplete()
81
82 async def running(self):
83 """True if the operation is currently running."""
84 result = await self.done()
85 return not result
86
87 async def _blocking_poll(self, timeout=None):
88 """Poll and await for the Future to be resolved.
89
90 Args:
91 timeout (int):
92 How long (in seconds) to wait for the operation to complete.
93 If None, wait indefinitely.
94 """
95 if self._future.done():
96 return
97
98 retry_ = self._retry.with_timeout(timeout)
99
100 try:
101 await retry_(self._done_or_raise)()
102 except exceptions.RetryError:
103 raise asyncio.TimeoutError(
104 "Operation did not complete within the designated " "timeout."
105 )
106
107 async def result(self, timeout=None):
108 """Get the result of the operation.
109
110 Args:
111 timeout (int):
112 How long (in seconds) to wait for the operation to complete.
113 If None, wait indefinitely.
114
115 Returns:
116 google.protobuf.Message: The Operation's result.
117
118 Raises:
119 google.api_core.GoogleAPICallError: If the operation errors or if
120 the timeout is reached before the operation completes.
121 """
122 await self._blocking_poll(timeout=timeout)
123 return self._future.result()
124
125 async def exception(self, timeout=None):
126 """Get the exception from the operation.
127
128 Args:
129 timeout (int): How long to wait for the operation to complete.
130 If None, wait indefinitely.
131
132 Returns:
133 Optional[google.api_core.GoogleAPICallError]: The operation's
134 error.
135 """
136 await self._blocking_poll(timeout=timeout)
137 return self._future.exception()
138
139 def add_done_callback(self, fn):
140 """Add a callback to be executed when the operation is complete.
141
142 If the operation is completed, the callback will be scheduled onto the
143 event loop. Otherwise, the callback will be stored and invoked when the
144 future is done.
145
146 Args:
147 fn (Callable[Future]): The callback to execute when the operation
148 is complete.
149 """
150 if self._background_task is None:
151 self._background_task = asyncio.get_event_loop().create_task(
152 self._blocking_poll()
153 )
154 self._future.add_done_callback(fn)
155
156 def set_result(self, result):
157 """Set the Future's result."""
158 self._future.set_result(result)
159
160 def set_exception(self, exception):
161 """Set the Future's exception."""
162 self._future.set_exception(exception)