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gh-140947: fix contextvars handling for server tasks in asyncio #141158

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Merged
kumaraditya303 merged 17 commits into from
Mar 21, 2026
Merged

gh-140947: fix contextvars handling for server tasks in asyncio #141158

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a7bf339
properly propagate contextvars for server protocols
kumaraditya303 Nov 3, 2025
40a8f7c
fix _add_writer
kumaraditya303 Dec 2, 2025
d786ca0
Merge branch 'main' of https://github.com/python/cpython into asyncio…
kumaraditya303 Dec 12, 2025
6990bb9
Merge branch 'main' of https://github.com/python/cpython into asyncio…
kumaraditya303 Jan 13, 2026
f845484
refactor 1
kumaraditya303 Jan 13, 2026
f556a84
all tests pass on mac
kumaraditya303 Jan 13, 2026
cbbf0c6
temp fix windows
kumaraditya303 Jan 13, 2026
ac7e954
Merge branch 'asyncio-contextvars-fix' of https://github.com/kumaradi…
kumaraditya303 Mar 21, 2026
b344e60
add tests
kumaraditya303 Mar 21, 2026
6a8e2bd
fix tests
kumaraditya303 Mar 21, 2026
ec0ed9b
add more windows tests
kumaraditya303 Mar 21, 2026
09df55e
fix ssl part
kumaraditya303 Mar 21, 2026
edcedbb
fix tests
kumaraditya303 Mar 21, 2026
e1ebe67
fix windows tests
kumaraditya303 Mar 21, 2026
c42e01c
Merge branch 'asyncio-contextvars-fix' of https://github.com/kumaradi…
kumaraditya303 Mar 21, 2026
a2039d6
📜🤖 Added by blurb_it.
blurb-it[bot] Mar 21, 2026
69874d5
fix tests on machine without ssl
kumaraditya303 Mar 21, 2026
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fix ssl part
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@kumaraditya303
kumaraditya303 committed Mar 21, 2026
commit 09df55ed3ef1ead05d86cc8e52da145336775c9d
6 changes: 4 additions & 2 deletions Lib/asyncio/base_events.py
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Original file line number Diff line number Diff line change
Expand Up @@ -511,7 +511,8 @@ def _make_ssl_transport(
extra=None, server=None,
ssl_handshake_timeout=None,
ssl_shutdown_timeout=None,
call_connection_made=True):
call_connection_made=True,
context=None):
"""Create SSL transport."""
raise NotImplementedError

Expand Down Expand Up @@ -1228,7 +1229,8 @@ async def _create_connection_transport(
sock, protocol, sslcontext, waiter,
server_side=server_side, server_hostname=server_hostname,
ssl_handshake_timeout=ssl_handshake_timeout,
ssl_shutdown_timeout=ssl_shutdown_timeout)
ssl_shutdown_timeout=ssl_shutdown_timeout,
context=context)
else:
transport = self._make_socket_transport(sock, protocol, waiter, context=context)

Expand Down
8 changes: 5 additions & 3 deletions Lib/asyncio/selector_events.py
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Original file line number Diff line number Diff line change
Expand Up @@ -78,16 +78,17 @@ def _make_ssl_transport(
extra=None, server=None,
ssl_handshake_timeout=constants.SSL_HANDSHAKE_TIMEOUT,
ssl_shutdown_timeout=constants.SSL_SHUTDOWN_TIMEOUT,
context=None,
):
self._ensure_fd_no_transport(rawsock)
ssl_protocol = sslproto.SSLProtocol(
self, protocol, sslcontext, waiter,
server_side, server_hostname,
ssl_handshake_timeout=ssl_handshake_timeout,
ssl_shutdown_timeout=ssl_shutdown_timeout
ssl_shutdown_timeout=ssl_shutdown_timeout,
)
_SelectorSocketTransport(self, rawsock, ssl_protocol,
extra=extra, server=server)
extra=extra, server=server, context=context)
return ssl_protocol._app_transport

def _make_datagram_transport(self, sock, protocol,
Expand Down Expand Up @@ -230,7 +231,8 @@ async def _accept_connection2(
conn, protocol, sslcontext, waiter=waiter,
server_side=True, extra=extra, server=server,
ssl_handshake_timeout=ssl_handshake_timeout,
ssl_shutdown_timeout=ssl_shutdown_timeout)
ssl_shutdown_timeout=ssl_shutdown_timeout,
context=context)
else:
transport = self._make_socket_transport(
conn, protocol, waiter=waiter, extra=extra,
Expand Down
82 changes: 59 additions & 23 deletions Lib/test/test_asyncio/test_server_context.py
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Original file line number Diff line number Diff line change
Expand Up @@ -5,11 +5,20 @@

from unittest import TestCase

try:
import ssl
except ImportError:
ssl = None

from test.test_asyncio import utils as test_utils

def tearDownModule():
asyncio.events._set_event_loop_policy(None)

class ServerContextvarsTestCase:
loop_factory = None # To be defined in subclasses
server_ssl_context = None # To be defined in subclasses for SSL tests
client_ssl_context = None # To be defined in subclasses for SSL tests

def run_coro(self, coro):
return asyncio.run(coro, loop_factory=self.loop_factory)
Expand All @@ -25,12 +34,14 @@ async def handle_client(reader, writer):
await writer.drain()
writer.close()

server = await asyncio.start_server(handle_client, '127.0.0.1', 0)
server = await asyncio.start_server(handle_client, '127.0.0.1', 0,
ssl=self.server_ssl_context)
# change the value
var.set("after_server")

async def client(addr):
reader, writer = await asyncio.open_connection(*addr)
reader, writer = await asyncio.open_connection(*addr,
ssl=self.client_ssl_context)
data = await reader.read(100)
writer.close()
await writer.wait_closed()
Expand All @@ -56,11 +67,13 @@ async def handle_client(reader, writer):
await writer.drain()
writer.close()

server = await asyncio.start_server(handle_client, '127.0.0.1', 0)
server = await asyncio.start_server(handle_client, '127.0.0.1', 0,
ssl=self.server_ssl_context)
var.set("after_server")

async def client(addr):
reader, writer = await asyncio.open_connection(*addr)
reader, writer = await asyncio.open_connection(*addr,
ssl=self.client_ssl_context)
data = await reader.read(100)
writer.close()
await writer.wait_closed()
Expand All @@ -87,11 +100,13 @@ async def handle_client(reader, writer):
await writer.drain()
writer.close()

server = await asyncio.start_server(handle_client, '127.0.0.1', 0)
server = await asyncio.start_server(handle_client, '127.0.0.1', 0,
ssl=self.server_ssl_context)
var.set("after_server")

async def client(addr):
reader, writer = await asyncio.open_connection(*addr)
reader, writer = await asyncio.open_connection(*addr,
ssl=self.client_ssl_context)
data = await reader.read(100)
self.assertEqual(data.decode(), "before_server")
writer.close()
Expand Down Expand Up @@ -122,11 +137,13 @@ def connection_made(self, transport):
self.transport.close()

server = await asyncio.get_running_loop().create_server(
lambda: EchoProtocol(), '127.0.0.1', 0)
lambda: EchoProtocol(), '127.0.0.1', 0,
ssl=self.server_ssl_context)
var.set("after_server")

async def client(addr):
reader, writer = await asyncio.open_connection(*addr)
reader, writer = await asyncio.open_connection(*addr,
ssl=self.client_ssl_context)
data = await reader.read(100)
self.assertEqual(data.decode(), "default")
writer.close()
Expand Down Expand Up @@ -157,12 +174,14 @@ def connection_made(self, transport):
self.transport.close()

server = await asyncio.get_running_loop().create_server(
lambda: EchoProtocol(), '127.0.0.1', 0)
lambda: EchoProtocol(), '127.0.0.1', 0,
ssl=self.server_ssl_context)

var.set("after_server")

async def client(addr, expected):
reader, writer = await asyncio.open_connection(*addr)
reader, writer = await asyncio.open_connection(*addr,
ssl=self.client_ssl_context)
data = await reader.read(100)
self.assertEqual(data.decode(), expected)
writer.close()
Expand All @@ -184,6 +203,7 @@ def test_gh140947(self):
cvar2 = contextvars.ContextVar("cvar2")
cvar3 = contextvars.ContextVar("cvar3")
results = {}
is_ssl = self.server_ssl_context is not None

def capture_context(meth):
result = []
Expand Down Expand Up @@ -218,36 +238,37 @@ def connection_lost(self, exc):

async def asgi(self):
capture_context("asgi start")

cvar1.set(True)

# make sure that we only resume after the pause
# otherwise the resume does nothing
while not self.transport._paused:
await asyncio.sleep(0.1)

if is_ssl:
while not self.transport._ssl_protocol._app_reading_paused:
await asyncio.sleep(0.01)
else:
while not self.transport._paused:
await asyncio.sleep(0.01)
cvar2.set(True)

self.transport.resume_reading()

cvar3.set(True)

capture_context("asgi end")


async def main():
loop = asyncio.get_running_loop()
on_conn_lost = loop.create_future()

host, port = "127.0.0.1", 8888

async with await loop.create_server(lambda: DemoProtocol(on_conn_lost), host, port):
reader, writer = await asyncio.open_connection(host, port)
server = await loop.create_server(
lambda: DemoProtocol(on_conn_lost), '127.0.0.1', 0,
ssl=self.server_ssl_context)
async with server:
addr = server.sockets[0].getsockname()
reader, writer = await asyncio.open_connection(*addr,
ssl=self.client_ssl_context)
writer.write(b"anything")
await writer.drain()
writer.close()
await writer.wait_closed()
await on_conn_lost

self.run_coro(main())
self.assertDictEqual(results, {
"connection_made": [],
Expand All @@ -261,12 +282,27 @@ async def main():
class AsyncioEventLoopTests(TestCase, ServerContextvarsTestCase):
loop_factory = staticmethod(asyncio.new_event_loop)

@unittest.skipUnless(ssl, "SSL not available")
class AsyncioEventLoopSSLTests(AsyncioEventLoopTests):
server_ssl_context = test_utils.simple_server_sslcontext()
client_ssl_context = test_utils.simple_client_sslcontext()

if sys.platform == "win32":
class AsyncioProactorEventLoopTests(TestCase, ServerContextvarsTestCase):
loop_factory = asyncio.ProactorEventLoop

class AsyncioSelectorEventLoopTests(TestCase, ServerContextvarsTestCase):
loop_factory = asyncio.SelectorEventLoop

@unittest.skipUnless(ssl, "SSL not available")
class AsyncioProactorEventLoopSSLTests(AsyncioProactorEventLoopTests):
server_ssl_context = test_utils.simple_server_sslcontext()
client_ssl_context = test_utils.simple_client_sslcontext()

@unittest.skipUnless(ssl, "SSL not available")
class AsyncioSelectorEventLoopSSLTests(AsyncioSelectorEventLoopTests):
server_ssl_context = test_utils.simple_server_sslcontext()
client_ssl_context = test_utils.simple_client_sslcontext()

if __name__ == "__main__":
unittest.main()
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