plba/requirements/Mail Order Bot Migration Plan.md

Mail Order Bot Migration Plan

Goal

Migrate mail_order_bot to the new PLBA model:

• application assembled by ApplicationModule
• runtime execution owned by Worker
• business behavior implemented in routines/services

Target structure

Application module

MailOrderBotModule should:

• build domain services
• build routines
• register workers
• register optional health contributors

Workers

Initial workers:

• MailPollingWorker
• EmailProcessingWorker
• optional ReconciliationWorker

Each worker should own only runtime behavior:

• start/stop
• execution loop
• thread model
• health/status

Routines

Initial routines:

• MailPollingRoutine
• EmailProcessingRoutine
• ReconciliationRoutine

Each routine should own business behavior:

• fetch messages
• parse message payload
• call domain services
• persist changes
• report business failures upward

Migration steps

1. Extract business logic from current worker-like components into routines/services.
2. Implement thin workers that call those routines.
3. Register workers from MailOrderBotModule.
4. Use runtime health and status only through worker state.
5. Keep any local queue only as an implementation detail if it still helps.

Optional queue usage

If email processing still benefits from buffering, InMemoryTaskQueue may be used inside the application.

Important:

• it should remain an app-level detail
• it should not define the platform contract
• the main architecture should still be described through workers and routines