This is a plugin for Trunk Recorder that publish the current status over MQTT. External programs can use the MQTT messages to collect and display information on monitored systems.

Requires trunk-recorder 4.7 (commit 837a057 14 NOV 2023) or later, and Paho MQTT libraries

• Install
• Configure
• MQTT Messages
• Trunk Recorder States
• MQTT Brokers
  • Mosquitto MQTT Broker
  • NanoMQ
• Docker

1. Build and install the current version of Trunk Recorder following these instructions. Make sure you do a sudo make install at the end to install the Trunk Recorder binary and libraries system-wide. The plugin will be built against these libraries.

2. Install the Paho MQTT C & C++ Libraries.

  Install Paho MQTT C

git clone https://github.com/eclipse/paho.mqtt.c.git
cd paho.mqtt.c

cmake -Bbuild -H. -DPAHO_ENABLE_TESTING=OFF -DPAHO_BUILD_STATIC=ON  -DPAHO_WITH_SSL=ON -DPAHO_HIGH_PERFORMANCE=ON
sudo cmake --build build/ --target install
sudo ldconfig

  Install Paho MQTT C++

git clone https://github.com/eclipse/paho.mqtt.cpp
cd paho.mqtt.cpp

cmake -Bbuild -H. -DPAHO_BUILD_STATIC=ON
sudo cmake --build build/ --target install
sudo ldconfig

  Alternatively, if your package manager provides recent Paho MQTT libraries:

sudo apt install libpaho-mqtt-dev libpaho-mqttpp-dev

3. Build and install the plugin:

  Plugin repos should be cloned in a location other than the trunk-recorder source dir.

mkdir build
cd build
cmake ..
sudo make install

  IMPORTANT NOTE: To avoid SEGFAULTs or other errors, plugins should be rebuilt after every new release of trunk-recorder.

Plugin options:

Trunk-Recorder options:

Plugin Usage:

See the included config.json for an example how to load this plugin.

    "plugins": [
    {
        "name": "MQTT Status",
        "library": "libmqtt_status_plugin.so",
        "broker": "tcp://io.adafruit.com:1883",
        "topic": "robotastic/feeds",
        "unit_topic": "robotastic/units",
        "username": "robotastic",
        "password": "",
        "console_logs": true,
    }]

If the plugin cannot be found, or it is being run from a different location, it may be necessary to supply the full path:

        "library": "/usr/local/lib/trunk-recorder/libmqtt_status_plugin.so",

The plugin will provide the following messages to the MQTT broker depending on configured topics.

* Some messages have been changed for consistency. Please see links for examples and notes.
** end is not a trunking message, but sent after trunk-recorder ends the call. This can be used to track conventional non-trunked calls.

Trunk Recorder uses state definitions to manage call flows, recorder assignment, and demodulator operation. The MQTT plugin will include this information when possible. Below is a summary of these states, but not all may appear in MQTT messages.

call_state / rec_state

mon_state

The Mosquitto MQTT is an easy way to have a local MQTT broker. It can be installed from a lot of package managers.

This broker does not impose a limit on the length of MQTT messages, and will handle packets up to 256 MB in size by default.

Starting it on a Mac:

/opt/homebrew/sbin/mosquitto -c /opt/homebrew/etc/mosquitto/mosquitto.conf

The NanoMQ broker is a lightweight alternative, but additional configuration may be required for Trunk Recorder systems with a large number of recorders or heavy call volume.

This broker does impose a limit on the length of MQTT messages, and the max_packet_size default of 10 KB may generate MQTT error [-3]: Disconnected errors with this plugin.

# #============================================================
# # NanoMQ Broker
# #============================================================

mqtt {
    property_size = 32
    max_packet_size = 10KB
    max_mqueue_len = 2048
    retry_interval = 10s
    keepalive_multiplier = 1.25
...

Editing /etc/nanomq.conf and increasing the packet size to 100 KB or more should be sufficient for MQTT messages generated by this plugin.

The included Dockerfile will allow building a trunk-recorder docker image with this plugin included.

docker-compose can be used to automate the build and deployment of this image. In the Docker compose file replace the image line with a build line pointing to the location where this repo has been cloned to.

Docker compose file:

version: "3"
services:
  recorder:
    build: ./trunk-recorder-mqtt-status
    container_name: trunk-recorder
    restart: always
    privileged: true
    volumes:
      - /dev/bus/usb:/dev/bus/usb
      - /var/run/dbus:/var/run/dbus
      - /var/run/avahi-daemon/socket:/var/run/avahi-daemon/socket
      - ./:/app