Add support for `after_connect` statements when `server_settings` are not supported

[mbrancato]

• asyncpg version: 0.27
• PostgreSQL version: 14
• Do you use a PostgreSQL SaaS? If so, which? Can you reproduce the issue with a local PostgreSQL install?: n/a
• Python version: 3.10
• Platform: Linux
• Do you use pgbouncer?: yes
• Did you install asyncpg with pip?: yes
• If you built asyncpg locally, which version of Cython did you use?:
• Can the issue be reproduced under both asyncio and uvloop?: n/a

In a very large environment, pooling along is not enough, and we use pgbouncer to help control connections to the DB. The problem is that pgbouncer does not support some of the parameters. This includes settings like statement_timeout and lock_timeout.

Other pooling libraries support a set of queries that run after connect and at other points in the connection lifecycle.

It would be nice if asyncpg could allow queries / exec to call SET in the connection before it enters the pool to enforce these settings.

[elprans]

It's already implemented, as the init kwarg to connect and create_pool:

pool = await asyncpg.create_pool(..., init=your_callback)

Is that what you're looking for?

[mbrancato]

Yes, I think that works. I didn't realize that form the docs.