Events

Event listener using Postgres LISTEN for pyfetcher.events.

class pyfetcher.events.listener.EventListener(config=None)

Listens for Postgres NOTIFY events on specified channels.

Uses a raw asyncpg connection (not SQLAlchemy) for LISTEN since SQLAlchemy’s async session doesn’t expose notification listeners.

Parameters:

config (PyfetcherConfig | None) – Application configuration with database URL.

on(channel, handler)

Register a handler for a channel.

Parameters:

• channel (str) – The channel to listen on.

• handler (Callable[[str], Coroutine[Any, Any, None]]) – Async callable receiving the notification payload.

Return type:

None

async start()

Start listening on all registered channels.

Runs indefinitely, dispatching notifications to registered handlers. Call stop() to shut down.

Return type:

None

async stop()

Stop listening and close the connection.

Return type:

None

NOTIFY channel constants for pyfetcher.events.

class pyfetcher.events.channels.Channels

Postgres NOTIFY channel names for pipeline stages.