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EventBroadcaster: Log and raise when listener task fails to connect #77

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Jun 27, 2024
Merged

EventBroadcaster: Log and raise when listener task fails to connect #77

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91 changes: 53 additions & 38 deletions fastapi_websocket_pubsub/event_broadcaster.py
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Original file line number Diff line number Diff line change
Expand Up @@ -65,7 +65,7 @@ async def __aenter__(self):
"Listening for incoming events from broadcast channel (first listener started)"
)
# Start task listening on incoming broadcasts
self._event_broadcaster.start_reader_task()
await self._event_broadcaster.start_reader_task()

if self._share:
self._event_broadcaster._share_count += 1
Expand Down Expand Up @@ -159,6 +159,7 @@ def __init__(
self._context_manager = None
self._context_manager_lock = asyncio.Lock()
self._tasks = set()
self.listening_broadcast_channel = None

async def __broadcast_notifications__(self, subscription: Subscription, data):
"""
Expand Down Expand Up @@ -221,9 +222,12 @@ async def __aenter__(self):
return await self._context_manager.__aenter__()

async def __aexit__(self, exc_type, exc, tb):
if self.listening_broadcast_channel is not None:
await self.listening_broadcast_channel.disconnect()
self.listening_broadcast_channel = None
await self._context_manager.__aexit__(exc_type, exc, tb)

def start_reader_task(self):
async def start_reader_task(self):
"""Spawn a task reading incoming broadcasts and posting them to the intreal notifier
Raises:
BroadcasterAlreadyStarted: if called more than once per context
Expand All @@ -237,6 +241,20 @@ def start_reader_task(self):
"No need for listen task, already started broadcast listen task for this notifier"
)
return

# Init new broadcast channel for reading
try:
if self.listening_broadcast_channel is None:
self.listening_broadcast_channel = self._broadcast_type(
self._broadcast_url
)
await self.listening_broadcast_channel.connect()
except Exception as e:
logger.error(
f"Failed to connect to broadcast channel for reading incoming events: {e}"
)
raise e

# Trigger the task
logger.debug("Spawning broadcast listen task")
self._subscription_task = asyncio.create_task(self.__read_notifications__())
Expand All @@ -249,44 +267,41 @@ async def __read_notifications__(self):
"""
read incoming broadcasts and posting them to the intreal notifier
"""
logger.info("Starting broadcaster listener")
# Init new broadcast channel for reading
listening_broadcast_channel = self._broadcast_type(self._broadcast_url)
async with listening_broadcast_channel:
# Subscribe to our channel
async with listening_broadcast_channel.subscribe(
channel=self._channel
) as subscriber:
async for event in subscriber:
try:
notification = BroadcastNotification.parse_raw(event.message)
# Avoid re-publishing our own broadcasts
if notification.notifier_id != self._id:
logger.debug(
"Handling incoming broadcast event: {}".format(
{
"topics": notification.topics,
"src": notification.notifier_id,
}
)
logger.debug("Starting broadcaster listener")
# Subscribe to our channel
async with self.listening_broadcast_channel.subscribe(
channel=self._channel
) as subscriber:
async for event in subscriber:
try:
notification = BroadcastNotification.parse_raw(event.message)
# Avoid re-publishing our own broadcasts
if notification.notifier_id != self._id:
logger.debug(
"Handling incoming broadcast event: {}".format(
{
"topics": notification.topics,
"src": notification.notifier_id,
}
)
# Notify subscribers of message received from broadcast
task = asyncio.create_task(
self._notifier.notify(
notification.topics,
notification.data,
notifier_id=self._id,
)
)
# Notify subscribers of message received from broadcast
task = asyncio.create_task(
self._notifier.notify(
notification.topics,
notification.data,
notifier_id=self._id,
)
)

self._tasks.add(task)
self._tasks.add(task)

def cleanup(task):
self._tasks.remove(task)
def cleanup(task):
self._tasks.remove(task)

task.add_done_callback(cleanup)
except:
logger.exception("Failed handling incoming broadcast")
logger.info(
"No more events to read from subscriber (underlying connection closed)"
)
task.add_done_callback(cleanup)
except:
logger.exception("Failed handling incoming broadcast")
logger.info(
"No more events to read from subscriber (underlying connection closed)"
)
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