feat(mikroorm-driver): add PostgreSQL LISTEN/NOTIFY for instant event processing

[jtomaszewski]

Summary

Adds PostgreSQL LISTEN/NOTIFY support for faster event processing as an alternative to polling. When a new event is inserted into the inbox/outbox table, a database trigger sends a notification that instantly triggers event processing, reducing latency from polling interval (default 30s) to near-instant.

Changes

• Core package:

  • Added EventListener interface with connect(), disconnect(), and events$ Observable
  • Modified RetryableInboxOutboxEventPoller to optionally accept an event listener and merge its events with polling
  • Polling continues as fallback for startup and missed notifications

• MikroORM driver package:

  • Added PostgreSQLEventListener implementation that uses pg LISTEN/NOTIFY
  • Takes MikroORM instance and extracts connection config automatically
  • Added migration with trigger/function for NOTIFY on INSERT
  • Includes automatic reconnection on connection errors

Usage

// In your module
import { PostgreSQLEventListener, EVENT_LISTENER_TOKEN } from '@nestixis/nestjs-inbox-outbox-mikroorm-driver';

@Module({
  providers: [
    {
      provide: EVENT_LISTENER_TOKEN,
      useFactory: (orm: MikroORM) => new PostgreSQLEventListener(orm),
      inject: [MikroORM],
    },
  ],
})
export class AppModule {}

Run the migration to create the trigger:

CREATE OR REPLACE FUNCTION notify_inbox_outbox_event() RETURNS TRIGGER AS $$
BEGIN
  PERFORM pg_notify('inbox_outbox_event', NEW.id::text);
  RETURN NEW;
END;
$$ LANGUAGE plpgsql;

CREATE TRIGGER inbox_outbox_event_notify
  AFTER INSERT ON inbox_outbox_transport_event
  FOR EACH ROW EXECUTE FUNCTION notify_inbox_outbox_event();

Test plan

• Unit tests for PostgreSQLEventListener
• Integration tests verifying instant event delivery via NOTIFY
• All existing tests continue to pass

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