tedge-agent still subscribes to legacy topics when running as a child device

[reubenmiller]

Describe the bug

When running the tedge-agent as a child device, it subscribes to the legacy tedge/ topics when it shouldn't. For instance, below is the log output showing the unwanted subscriptions:

2024-07-31T16:48:56.526015106Z  INFO sm-agent: tedge_agent::agent: Running as a child device, tedge_to_te_converter and File Transfer Service disabled
2024-07-31T16:48:56.526161588Z  INFO Runtime: Running Signal-Handler-0
2024-07-31T16:48:56.52627807Z  INFO sm-agent: MQTT sub: te/device/pump///cmd/+/+
2024-07-31T16:48:56.526385737Z  INFO sm-agent: MQTT sub: te/device/pump/service/tedge-agent/cmd/health/check
2024-07-31T16:48:56.526485459Z  INFO sm-agent: MQTT sub: tedge/measurements
2024-07-31T16:48:56.526583163Z  INFO sm-agent: MQTT sub: tedge/measurements/+
2024-07-31T16:48:56.526677182Z  INFO sm-agent: MQTT sub: tedge/events/+
2024-07-31T16:48:56.526770423Z  INFO sm-agent: MQTT sub: tedge/events/+/+
2024-07-31T16:48:56.526864553Z  INFO sm-agent: MQTT sub: tedge/alarms/+/+
2024-07-31T16:48:56.527146443Z  INFO sm-agent: MQTT sub: tedge/alarms/+/+/+
2024-07-31T16:48:56.52724835Z  WARN sm-agent: MQTT sub: ignoring overlapping subscription to te/device/pump///cmd/health/check

Background

The tedge-agent includes a legacy topic converter, however it is only activated when the tedge-agent is running as the main device (e.g. te/device/main//). When running as a child device, the converter is not running (which is correct), however the topic converter builder already alters the MQTT actor and adds the subscriptions to the legacy topics.

To Reproduce

Run the tedge-agent as a child device for a few seconds and inspect the log output to see the subscriptions:

TEDGE_RUN_LOCK_FILES=false timeout 5 tedge-agent --mqtt-device-topic-id "device/pump//"

Below are the examples of the legacy topics that should not be subscribed to when running as a child device.

2024-07-31T16:48:56.526485459Z  INFO sm-agent: MQTT sub: tedge/measurements
2024-07-31T16:48:56.526583163Z  INFO sm-agent: MQTT sub: tedge/measurements/+
2024-07-31T16:48:56.526677182Z  INFO sm-agent: MQTT sub: tedge/events/+
2024-07-31T16:48:56.526770423Z  INFO sm-agent: MQTT sub: tedge/events/+/+
2024-07-31T16:48:56.526864553Z  INFO sm-agent: MQTT sub: tedge/alarms/+/+
2024-07-31T16:48:56.527146443Z  INFO sm-agent: MQTT sub: tedge/alarms/+/+/+

Expected behavior

When the tedge-agent is running as a child device, it should not subscribe to tedge/# topics.

Screenshots

Environment (please complete the following information):

Property	Value
OS [incl. version]	Debian GNU/Linux 12 (bookworm)
Hardware [incl. revision]	Raspberry Pi 5 Model B Rev 1.0
System-Architecture	Linux rpi5-d83add9f145a 6.1.0-rpi7-rpi-2712 #1 SMP PREEMPT Debian 1:6.1.63-1+rpt1 (2023-11-24) aarch64 GNU/Linux
thin-edge.io version	tedge 1.1.2~326+g2a9eed4
mosquitto version	2.0.18

Additional context

[reubenmiller]

The linked PR includes a system test.