Easy change of default connection pool class

[stinovlas]

PsycopgConnector currently uses psycopg_pool.AsyncConnectionPool by default. It's possible to pass pool argument to App.open_async which overrides this, but it's not as easy to pass it to procrastinate worker / defer CLI commands. I ended up with overriding open_async method of PsycopgConnector like this:

import psycopg_pool
from procrastinate import PsycopgConnector

class NullPoolPsycopgConnector(PsycopgConnector):
    async def open_async(self, pool: psycopg_pool.AsyncConnectionPool | None = None) -> None:
        """Override open_async to use null connection pool by default."""
        if pool is None:
            pool = psycopg_pool.AsyncNullConnectionPool(**self._pool_args)
        return await super().open_async(pool)

This works, but it doesn't feel very clean. I'd rather have connection_pool_cls kwarg on PsycopgConnector where I could pass AsyncNullConnectionPool (or any other class inheriting from AsyncConnectionPool). If specified, this class would be used instead of AsyncConnectionPool in PsycopgConnector._create_pool. It would be used like this:

app = TasksApp(
    connector=PsycopgConnector(
        connection_pool_cls=psycopg_pool.AsyncNullConnectionPool,
        json_dumps=orjson.dumps,
        json_loads=orjson.loads,
        **connector_options
    ),
    import_paths=[...],
)

What do you think?

[ewjoachim]

It makes sense, I like it. I wonder if it should be a "pool class" or a "pool factory" (those are conceptually the same thing: a callable that returns a pool instance), but it could well be any other callable and not a class)

Would you like to contribute this ?

[stinovlas]

Pool factory sounds good 🙂. I'll look into it in the upcoming week.

[ewjoachim]

#1022