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[ServiceBus] Fix async sender AttributeError race in _open (#35618) #46683

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[ServiceBus] Fix async sender AttributeError race in _open (#35618) #46683

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78fb508
fix(servicebus): guard async sender against handler race in _open
May 2, 2026
f568e44
address review: serialize _open() with asyncio.Lock
SAY-5 May 3, 2026
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6 changes: 6 additions & 0 deletions sdk/servicebus/azure-servicebus/CHANGELOG.md
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Original file line number Diff line number Diff line change
@@ -1,5 +1,11 @@
# Release History

## 7.14.4 (Unreleased)

### Bugs Fixed

- Fixed a race condition in the async ServiceBusSender where concurrent coroutines could trigger `AttributeError: 'NoneType' object has no attribute 'client_ready_async'` when reusing a sender. ([#35618](https://github.com/Azure/azure-sdk-for-python/issues/35618))

## 7.14.3 (2025-11-11)

### Bugs Fixed
Expand Down
48 changes: 29 additions & 19 deletions sdk/servicebus/azure-servicebus/azure/servicebus/aio/_servicebus_sender_async.py
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Original file line number Diff line number Diff line change
Expand Up @@ -146,6 +146,10 @@ def __init__(
self._create_attribute(**kwargs)
self._connection = kwargs.get("connection")
self._handler: Union["pyamqp_SendClientAsync", "uamqp_SendClientAsync"]
# Serializes _open() so concurrent callers cannot race on creating
# and closing self._handler (see issue #35618). Initialized lazily
# because the constructor may execute outside a running event loop.
self._open_lock: Optional[asyncio.Lock] = None

async def __aenter__(self) -> "ServiceBusSender":
if self._shutdown.is_set():
Expand Down Expand Up @@ -203,25 +207,31 @@ def _create_handler(self, auth: Union["uamqp_JWTTokenAuthAsync", "pyamqp_JWTToke
async def _open(self):
if self._running:
return
if self._handler:
await self._handler.close_async()
auth = None if self._connection else (await create_authentication(self))
self._create_handler(auth)
try:
await self._handler.open_async(connection=self._connection)
while not await self._handler.client_ready_async():
await asyncio.sleep(0.05)
self._running = True
self._max_message_size_on_link = (
self._amqp_transport.get_remote_max_message_size(self._handler) or MAX_MESSAGE_LENGTH_BYTES
)
if self._max_message_size_on_link >= MAX_BATCH_SIZE_PREMIUM:
self._max_batch_size_on_link = MAX_BATCH_SIZE_PREMIUM
else:
self._max_batch_size_on_link = MAX_BATCH_SIZE_STANDARD
except:
await self._close_handler()
raise
if self._open_lock is None:
self._open_lock = asyncio.Lock()
async with self._open_lock:
if self._running:
return
if self._handler:
await self._handler.close_async()
auth = None if self._connection else (await create_authentication(self))
self._create_handler(auth)
handler = self._handler
try:
await handler.open_async(connection=self._connection)
while not await handler.client_ready_async():
await asyncio.sleep(0.05)
self._running = True
self._max_message_size_on_link = (
self._amqp_transport.get_remote_max_message_size(handler) or MAX_MESSAGE_LENGTH_BYTES
)
if self._max_message_size_on_link >= MAX_BATCH_SIZE_PREMIUM:
self._max_batch_size_on_link = MAX_BATCH_SIZE_PREMIUM
else:
self._max_batch_size_on_link = MAX_BATCH_SIZE_STANDARD
except:
await self._close_handler()
raise

async def _send(
self,
Expand Down
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