Listener Short Lifespan

[arcanefeenix]

• asyncpg version: 0.12.0
• PostgreSQL version: 9.4.12
• Python version: 3.6.1
• Platform: Windows x64
• Do you use pgbouncer?: No
• Did you install asyncpg with pip?: Yes
• If you built asyncpg locally, which version of Cython did you use?: N/A
• Can the issue be reproduced under both asyncio and uvloop?: Unknown

When using conn.add_listener(), the listener only seems to be listening for NOTIFY messages immediately afterwards. If I execute the following code:

async with Database(self.bot) as db:
   async with db.pool.acquire() as conn:
      await conn.add_listener('announcements', listener)
      await conn.execute('NOTIFY "announcements", \'Test!\'')

I receive the notification in the log. If I just add the listener and execute the NOTIFY line elsewhere, it is not received. Also NOTIFY messages from other sources (such as the server via command line or function/trigger) are not received as well. Am I using the add_listener call incorrectly? Is the listener dropped after this call is complete?

Thanks for any help you can offer.

[elprans]

The code is incorrect. You are attempting to listen on a short-lived connection, which is returned to the pool once the async with pool.acquire() block is exited. Your listener is removed once the connection is returned to the pool.

The proper way is to open a long-lived connection and listen on that.

conn = await asyncpg.connect()
await conn.add_listener('announcements', listener)

# ... later, when done listening
await conn.remove_listener('announcements', listener)
await conn.close()

[elprans]

On a second thought, we should probably issue a warning when a connection is returned to the pool with unclosed listeners to give a better hint. I just opened #190 for that.

[vladyslav2]

@elprans thanks for a warning
I start digging a code and found out what I did wrong