https://github.com/python/cpython/commit/7d435cfde6bd2b4b7f313eb20b53a1777e6c56d3
commit: 7d435cfde6bd2b4b7f313eb20b53a1777e6c56d3
branch: main
author: Bruce Merry <[email protected]>
committer: kumaraditya303 <[email protected]>
date: 2025-09-08T21:39:52+05:30
summary:
gh-136234: Fix `SelectorSocketTransport.writelines` to be robust to connection
loss (#136743)
files:
A Misc/NEWS.d/next/Library/2025-07-17-16-12-23.gh-issue-136234.VmTxtj.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 3505d4bb6bd1f7..a7e27ccf0aa856 100644
--- a/Lib/asyncio/selector_events.py
+++ b/Lib/asyncio/selector_events.py
@@ -1174,6 +1174,13 @@ def writelines(self, list_of_data):
raise RuntimeError('unable to writelines; sendfile is in progress')
if not list_of_data:
return
+
+ if self._conn_lost:
+ if self._conn_lost >= constants.LOG_THRESHOLD_FOR_CONNLOST_WRITES:
+ logger.warning('socket.send() raised exception.')
+ self._conn_lost += 1
+ return
+
self._buffer.extend([memoryview(data) for data in list_of_data])
self._write_ready()
# If the entire buffer couldn't be written, register a write handler
diff --git a/Lib/test/test_asyncio/test_selector_events.py
b/Lib/test/test_asyncio/test_selector_events.py
index 9d77e7e5889d61..4bb5d4fb816a9a 100644
--- a/Lib/test/test_asyncio/test_selector_events.py
+++ b/Lib/test/test_asyncio/test_selector_events.py
@@ -854,6 +854,22 @@ def test_writelines_pauses_protocol(self):
self.assertTrue(self.sock.send.called)
self.assertTrue(self.loop.writers)
+ def test_writelines_after_connection_lost(self):
+ # GH-136234
+ transport = self.socket_transport()
+ self.sock.send = mock.Mock()
+ self.sock.send.side_effect = ConnectionResetError
+ transport.write(b'data1') # Will fail immediately, causing connection
lost
+
+ transport.writelines([b'data2'])
+ self.assertFalse(transport._buffer)
+ self.assertFalse(self.loop.writers)
+
+ test_utils.run_briefly(self.loop) # Allow _call_connection_lost to run
+ transport.writelines([b'data2'])
+ self.assertFalse(transport._buffer)
+ self.assertFalse(self.loop.writers)
+
@unittest.skipUnless(selector_events._HAS_SENDMSG, 'no sendmsg')
def test_write_sendmsg_full(self):
data = memoryview(b'data')
diff --git
a/Misc/NEWS.d/next/Library/2025-07-17-16-12-23.gh-issue-136234.VmTxtj.rst
b/Misc/NEWS.d/next/Library/2025-07-17-16-12-23.gh-issue-136234.VmTxtj.rst
new file mode 100644
index 00000000000000..044a601c9170a1
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2025-07-17-16-12-23.gh-issue-136234.VmTxtj.rst
@@ -0,0 +1,2 @@
+Fix :meth:`asyncio.WriteTransport.writelines` to be robust to connection
+failure, by using the same behavior as :meth:`~asyncio.WriteTransport.write`.
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