https://github.com/python/cpython/commit/109f7597d29f0b504e9b42cb398b44177157abaa
commit: 109f7597d29f0b504e9b42cb398b44177157abaa
branch: main
author: Christian Harries <68507104+christian...@users.noreply.github.com>
committer: ambv <luk...@langa.pl>
date: 2025-05-21T15:59:09+02:00
summary:
gh-90871: fix connection backlog offset in asyncio (gh-134392)
Co-authored-by: Łukasz Langa <luk...@langa.pl>
Co-authored-by: Kumar Aditya <kumaradi...@python.org>
files:
A Misc/NEWS.d/next/Library/2025-05-20-21-45-58.gh-issue-90871.Gkvtp6.rst
M Lib/asyncio/selector_events.py
M Lib/test/test_asyncio/test_selector_events.py
diff --git a/Lib/asyncio/selector_events.py b/Lib/asyncio/selector_events.py
index 22147451fa7ebd..6ad84044adf146 100644
--- a/Lib/asyncio/selector_events.py
+++ b/Lib/asyncio/selector_events.py
@@ -173,7 +173,7 @@ def _accept_connection(
# listening socket has triggered an EVENT_READ. There may be multiple
# connections waiting for an .accept() so it is called in a loop.
# See https://bugs.python.org/issue27906 for more details.
- for _ in range(backlog):
+ for _ in range(backlog + 1):
try:
conn, addr = sock.accept()
if self._debug:
diff --git a/Lib/test/test_asyncio/test_selector_events.py
b/Lib/test/test_asyncio/test_selector_events.py
index de81936b7456f2..aab6a779170eb9 100644
--- a/Lib/test/test_asyncio/test_selector_events.py
+++ b/Lib/test/test_asyncio/test_selector_events.py
@@ -347,6 +347,18 @@ def test_process_events_write_cancelled(self):
selectors.EVENT_WRITE)])
self.loop._remove_writer.assert_called_with(1)
+ def test_accept_connection_zero_one(self):
+ for backlog in [0, 1]:
+ sock = mock.Mock()
+ sock.accept.return_value = (mock.Mock(), mock.Mock())
+ with self.subTest(backlog):
+ mock_obj = mock.patch.object
+ with mock_obj(self.loop, '_accept_connection2') as
accept2_mock:
+ self.loop._accept_connection(
+ mock.Mock(), sock, backlog=backlog)
+ self.loop.run_until_complete(asyncio.sleep(0))
+ self.assertEqual(sock.accept.call_count, backlog + 1)
+
def test_accept_connection_multiple(self):
sock = mock.Mock()
sock.accept.return_value = (mock.Mock(), mock.Mock())
@@ -362,7 +374,7 @@ def test_accept_connection_multiple(self):
self.loop._accept_connection(
mock.Mock(), sock, backlog=backlog)
self.loop.run_until_complete(asyncio.sleep(0))
- self.assertEqual(sock.accept.call_count, backlog)
+ self.assertEqual(sock.accept.call_count, backlog + 1)
def test_accept_connection_skip_connectionabortederror(self):
sock = mock.Mock()
@@ -388,7 +400,7 @@ def mock_sock_accept():
# as in test_accept_connection_multiple avoid task pending
# warnings by using asyncio.sleep(0)
self.loop.run_until_complete(asyncio.sleep(0))
- self.assertEqual(sock.accept.call_count, backlog)
+ self.assertEqual(sock.accept.call_count, backlog + 1)
class SelectorTransportTests(test_utils.TestCase):
diff --git
a/Misc/NEWS.d/next/Library/2025-05-20-21-45-58.gh-issue-90871.Gkvtp6.rst
b/Misc/NEWS.d/next/Library/2025-05-20-21-45-58.gh-issue-90871.Gkvtp6.rst
new file mode 100644
index 00000000000000..49397c9705ecfe
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-05-20-21-45-58.gh-issue-90871.Gkvtp6.rst
@@ -0,0 +1,2 @@
+Fixed an off by one error concerning the backlog parameter in
+:meth:`~asyncio.loop.create_unix_server`. Contributed by Christian Harries.
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