aioble peripheral may need throttling to avoid random disconnects

aioble の characteristic 通知パスを、報告された概念コードおよび 50 ms の遅延時のその動作と併せて確認してください。指定された ESP32-C3 と MicroPython の構成で、短い間隔で連続する通知がどのようにクライアントの切断につながるかを確認してください。報告された不安定性を防ぐ、合意済みのレート制限または警告のアプローチを提示できれば完了です。

I am using AIOBLE (latest version as per December 2022) on ESP32-C3 with Micropython 1.19 (LOLIN D32 board).
My app uses 3 BT LE services (peripheral role),:

• a custom service for requests (with 1 write-only and 1notify-only characteristics)
• a battery_service
• a device_information service

I observed frequent client disconnects to client (I tested with another ESP32 and with NRFConnect app on Android).
The problem seems to happen more frequently when many requests were done in a rapid succession. In such conditions, the peripheral stopped responding, and disconnected the clients after a while (10-20s). Once the clients reconnected, everything worked again.

I was able to solve the problem after one week of testing, by imposing a minimum delay between all characteristics notifications (in my case 50 ms) : now I don't have any disconnects and everything is stable.

Concept code:

            since_last = time.ticks_ms() - __last_notification_ms
            while _MIN_BLUETOOTH_DELAY_MS > since_last > 0 and not force:
                await asyncio.sleep_ms(_MIN_BLUETOOTH_DELAY_MS - since_last)
                # Need to recheck because another transmission may have happened during await period
                since_last = time.ticks_ms() - __last_notification_ms
            data = __get_notification_data()
            __status_characteristic.write(data, True)
            __last_notification_ms = time.ticks_ms()

I guess there is a minimum delay for physical transmission over bluetooth and handling by RTOS and if we push too many notifications in a short period, something goes wrong. I wrote this issue for informing other AIOBLE users and for suggesting defining a rate limit inside the aioble library, or a warning, because this was quite difficult to troubleshoot.