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Postgres backend: handle connection loss #66

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Postgres backend: handle connection loss #66

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8 changes: 6 additions & 2 deletions broadcaster/_backends/postgres.py
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Original file line number Diff line number Diff line change
Expand Up @@ -14,6 +14,7 @@ def __init__(self, url: str):
async def connect(self) -> None:
self._conn = await asyncpg.connect(self._url)
self._listen_queue: asyncio.Queue = asyncio.Queue()
self._conn.add_termination_listener(self._termination_listener)

async def disconnect(self) -> None:
await self._conn.close()
Expand All @@ -27,10 +28,13 @@ async def unsubscribe(self, channel: str) -> None:
async def publish(self, channel: str, message: str) -> None:
await self._conn.execute("SELECT pg_notify($1, $2);", channel, message)

def _listener(self, *args: Any) -> None:
async def _listener(self, *args: Any) -> None:
connection, pid, channel, payload = args
event = Event(channel=channel, message=payload)
self._listen_queue.put_nowait(event)
await self._listen_queue.put(event)

async def _termination_listener(self, *args: Any) -> None:
await self._listen_queue.put(None)

async def next_published(self) -> Event:
return await self._listen_queue.get()
8 changes: 8 additions & 0 deletions broadcaster/_base.py
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Original file line number Diff line number Diff line change
Expand Up @@ -72,9 +72,17 @@ async def disconnect(self) -> None:
async def _listener(self) -> None:
while True:
event = await self._backend.next_published()
if event is None:
# Backend is disconnected
break

for queue in list(self._subscribers.get(event.channel, [])):
await queue.put(event)

# Ubsubscribe all
for queue in sum([list(qs) for qs in self._subscribers.values()], []):
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# Unsubscribe all
for queue_set in self._subscribers.values():
    for queue in queue_set:
        await queue.put(None)

Seems like a lot less wasteful / clear what's going on.
As far as I know, you can loop over sets directly in python, no need
to convert to a list.

await queue.put(None)

async def publish(self, channel: str, message: Any) -> None:
await self._backend.publish(channel, message)

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