Shutdown method in communication library

[ridax67]

When using VPP mode, I believe the inverter will be locked into VPP mode unless you set it back to TOU mode manually. It would be nice if the addon could implement a shutdown_hardware method that is called when ending the same way initialize_hardware is called when starting so you could clean up afterwards as users will be confused if their inverter doesn't allow control anymore after this sw has been running.

Do addons get notification when being stopped or do you need to hook SIGTERM?

[bess-agent]

Closing the loop on this one while auditing the VPP fixes before the next release — it was resolved, but by a different mechanism than you asked for, and nobody said so at the time.

There is no shutdown_hardware hook. What exists instead is two things that together cover the same ground:

1. leave_control_mode — on a deliberate switch of platform or control mode, VPP Status is read and disabled before the new controller is built. That is what Disabling of Vpp status setting #479 added, and it reads live hardware state rather than internal state, so it also recovers an install already stuck from before the fix.
2. The 20-minute VPP fallback timer — rewritten every active period (Vpp fall back to load first? #404), so if BESS stops writing for any reason the inverter reverts to load_first on its own.

The reason it went this way rather than as a shutdown hook: a hook cannot run on a crash, a container kill, or a host power loss, which are exactly the cases where being stuck in VPP would matter most. The dead-man's-switch covers all of them; the hook would only cover the clean-exit case, which leave_control_mode already handles.

So the request is satisfied, but the design answer was never written down where you could see it. If there is a case you have hit where neither path fires and the inverter stays in VPP, that is a real gap and worth reopening.

[johanzander]

Correcting the agent here, leave_control_mode is the correct method, the VPP timer would not turn off VPP mode.