From 361b09dde7de3c7314d7cac7447e029a8e54c97b Mon Sep 17 00:00:00 2001
From: Maxim Musayev <shamanu4@gmail.com>
Date: Mon, 16 Nov 2020 13:28:23 +0200
Subject: [PATCH] Fix commited offset is always behind the real offset by 1

---
 faust/transport/consumer.py           |  6 +++---
 tests/unit/transport/test_consumer.py | 19 ++++++++++---------
 2 files changed, 13 insertions(+), 12 deletions(-)

diff --git a/faust/transport/consumer.py b/faust/transport/consumer.py
index f8294e78b..6cdb8b884 100644
--- a/faust/transport/consumer.py
+++ b/faust/transport/consumer.py
@@ -739,7 +739,7 @@ def ack(self, message: Message) -> bool:
             if self.app.topics.acks_enabled_for(message.topic):
                 committed = self._committed_offset[tp]
                 try:
-                    if committed is None or offset > committed:
+                    if committed is None or offset >= committed:
                         acked_index = self._acked_index[tp]
                         if offset not in acked_index:
                             self._unacked_messages.discard(message)
@@ -1028,7 +1028,7 @@ def _new_offset(self, tp: TP) -> Optional[int]:
             acked[: len(batch) - 1] = []
             self._acked_index[tp].difference_update(batch)
             # return the highest commit offset
-            return batch[-1]
+            return batch[-1] + 1
         return None
 
     async def on_task_error(self, exc: BaseException) -> None:
@@ -1081,7 +1081,7 @@ async def _drain_messages(self, fetcher: ServiceT) -> None:  # pragma: no cover
 
                         offset = message.offset
                         r_offset = get_read_offset(tp)
-                        if r_offset is None or offset > r_offset:
+                        if r_offset is None or offset >= r_offset:
                             gap = offset - (r_offset or 0)
                             # We have a gap in income messages
                             if gap > 1 and r_offset:
diff --git a/tests/unit/transport/test_consumer.py b/tests/unit/transport/test_consumer.py
index 4517b58ae..3b79425ab 100644
--- a/tests/unit/transport/test_consumer.py
+++ b/tests/unit/transport/test_consumer.py
@@ -858,7 +858,8 @@ def test_filter_committable_offsets(self, *, consumer):
             TP2: 30,
         }
         assert consumer._filter_committable_offsets({TP1, TP2}) == {
-            TP2: 36,
+            TP1: 5,
+            TP2: 37,
         }
 
     @pytest.mark.asyncio
@@ -1015,10 +1016,10 @@ def test_should_commit(self, tp, offset, committed, should, *, consumer):
         "tp,acked,expected_offset",
         [
             (TP1, [], None),
-            (TP1, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10], 10),
-            (TP1, [1, 2, 3, 4, 5, 6, 7, 8, 10], 8),
-            (TP1, [1, 2, 3, 4, 6, 7, 8, 10], 4),
-            (TP1, [1, 3, 4, 6, 7, 8, 10], 1),
+            (TP1, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10], 11),
+            (TP1, [1, 2, 3, 4, 5, 6, 7, 8, 10], 9),
+            (TP1, [1, 2, 3, 4, 6, 7, 8, 10], 5),
+            (TP1, [1, 3, 4, 6, 7, 8, 10], 2),
         ],
     )
     def test_new_offset(self, tp, acked, expected_offset, *, consumer):
@@ -1029,10 +1030,10 @@ def test_new_offset(self, tp, acked, expected_offset, *, consumer):
         "tp,acked,gaps,expected_offset",
         [
             (TP1, [], [], None),
-            (TP1, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10], [], 10),
-            (TP1, [1, 2, 3, 4, 5, 6, 7, 8, 10], [9], 10),
-            (TP1, [1, 2, 3, 4, 6, 7, 8, 10], [5], 8),
-            (TP1, [1, 3, 4, 6, 7, 8, 10], [2, 5, 9], 10),
+            (TP1, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10], [], 11),
+            (TP1, [1, 2, 3, 4, 5, 6, 7, 8, 10], [9], 11),
+            (TP1, [1, 2, 3, 4, 6, 7, 8, 10], [5], 9),
+            (TP1, [1, 3, 4, 6, 7, 8, 10], [2, 5, 9], 11),
         ],
     )
     def test_new_offset_with_gaps(self, tp, acked, gaps, expected_offset, *, consumer):