feat: return singleton success future for exactly-once methods in Message (#608)

* Return singleton success future for exactly-once methods in subscriber.Message

Author: pradn

google/cloud/pubsub_v1/subscriber/message.py

@@ -40,6 +40,9 @@
  attributes: {}
 }}"""
 
+_SUCCESS_FUTURE = futures.Future()
+_SUCCESS_FUTURE.set_result(AcknowledgeStatus.SUCCESS)
+
 
 def _indent(lines: str, prefix: str = " ") -> str:
  """Indent some text.
@@ -291,12 +294,13 @@ def ack_with_response(self) -> "futures.Future":
  pubsub_v1.subscriber.exceptions.AcknowledgeError exception
  will be thrown.
  """
- future = futures.Future()
- req_future = None
+ req_future: Optional[futures.Future]
  if self._exactly_once_delivery_enabled_func():
+ future = futures.Future()
  req_future = future
  else:
- future.set_result(AcknowledgeStatus.SUCCESS)
+ future = _SUCCESS_FUTURE
+ req_future = None
  time_to_ack = math.ceil(time.time() - self._received_timestamp)
  self._request_queue.put(
  requests.AckRequest(
@@ -390,12 +394,13 @@ def modify_ack_deadline_with_response(self, seconds: int) -> "futures.Future":
  will be thrown.
 
  """
- future = futures.Future()
- req_future = None
+ req_future: Optional[futures.Future]
  if self._exactly_once_delivery_enabled_func():
+ future = futures.Future()
  req_future = future
  else:
- future.set_result(AcknowledgeStatus.SUCCESS)
+ future = _SUCCESS_FUTURE
+ req_future = None
 
  self._request_queue.put(
  requests.ModAckRequest(
@@ -451,12 +456,13 @@ def nack_with_response(self) -> "futures.Future":
  will be thrown.
 
  """
- future = futures.Future()
- req_future = None
+ req_future: Optional[futures.Future]
  if self._exactly_once_delivery_enabled_func():
+ future = futures.Future()
  req_future = future
  else:
- future.set_result(AcknowledgeStatus.SUCCESS)
+ future = _SUCCESS_FUTURE
+ req_future = None
 
  self._request_queue.put(
  requests.NackRequest(

tests/unit/pubsub_v1/subscriber/test_message.py

@@ -156,6 +156,7 @@ def test_ack_with_response_exactly_once_delivery_disabled():
  )
  )
  assert future.result() == AcknowledgeStatus.SUCCESS
+ assert future == message._SUCCESS_FUTURE
  check_call_types(put, requests.AckRequest)
 
 
@@ -205,6 +206,7 @@ def test_modify_ack_deadline_with_response_exactly_once_delivery_disabled():
  requests.ModAckRequest(ack_id="bogus_ack_id", seconds=60, future=None)
  )
  assert future.result() == AcknowledgeStatus.SUCCESS
+ assert future == message._SUCCESS_FUTURE
  check_call_types(put, requests.ModAckRequest)
 
 
@@ -242,6 +244,7 @@ def test_nack_with_response_exactly_once_delivery_disabled():
  )
  )
  assert future.result() == AcknowledgeStatus.SUCCESS
+ assert future == message._SUCCESS_FUTURE
  check_call_types(put, requests.NackRequest)