fix: Increment ack generation id (#203)

* fix: Increment ack generation id

Also handle duplicate acks.

* Remove duplicate acks change

google/cloud/pubsublite/cloudpubsub/internal/single_partition_subscriber.py

@@ -96,7 +96,7 @@ def __init__(
 
     async def handle_reset(self):
         # Increment ack generation id to ignore unacked messages.
-        ++self._ack_generation_id
+        self._ack_generation_id += 1
         await self._ack_set_tracker.clear_and_commit()
 
     async def read(self) -> Message:

tests/unit/pubsublite/cloudpubsub/internal/single_partition_subscriber_test.py

@@ -13,6 +13,7 @@
 # limitations under the License.
 
 import asyncio
+import json
 from typing import Callable
 
 from asynctest.mock import MagicMock, call
@@ -47,6 +48,10 @@ def mock_async_context_manager(cm):
     return cm
 
 
+def ack_id(generation, offset) -> str:
+    return json.dumps({"generation": generation, "offset": offset})
+
+
 @pytest.fixture()
 def underlying():
     return mock_async_context_manager(MagicMock(spec=Subscriber))
@@ -259,28 +264,21 @@ async def test_handle_reset(
         read_1: Message = await subscriber.read()
         ack_set_tracker.track.assert_has_calls([call(1)])
         assert read_1.message_id == "1"
+        assert read_1.ack_id == ack_id(0, 1)
 
         await subscriber.handle_reset()
         ack_set_tracker.clear_and_commit.assert_called_once()
 
-        # After reset, flow control tokens of unacked messages are refilled,
-        # but offset not committed.
+        # Message ACKed after reset. Its flow control tokens are refilled
+        # but offset not committed (verified below after message 2).
         read_1.ack()
-        await ack_called_queue.get()
-        await ack_result_queue.put(None)
-        underlying.allow_flow.assert_has_calls(
-            [
-                call(FlowControlRequest(allowed_messages=1000, allowed_bytes=1000,)),
-                call(FlowControlRequest(allowed_messages=1, allowed_bytes=5,)),
-            ]
-        )
-        ack_set_tracker.ack.assert_has_calls([])
 
         message_2 = SequencedMessage(cursor=Cursor(offset=2), size_bytes=10)
         underlying.read.return_value = message_2
         read_2: Message = await subscriber.read()
         ack_set_tracker.track.assert_has_calls([call(1), call(2)])
         assert read_2.message_id == "2"
+        assert read_2.ack_id == ack_id(1, 2)
         read_2.ack()
         await ack_called_queue.get()
         await ack_result_queue.put(None)