OwnTracks-to-ntfy setup variants

About

This section informs you about additional configuration and operation variants of the Forward OwnTracks low-battery warnings to ntfy recipe. For example, you may want to use Docker or Podman to run both mqttwarn and ntfy, or you may want to use another language than Python to implement your filtering function.

Docker and Podman

Running mqttwarn as container

This command will run mqttwarn in a container, using the docker command to launch it. Alternatively, podman can be used. It expects an MQTT broker to be running on localhost, so it uses the --network=host option. The command will mount the configuration file and the user-defined functions file correctly, and will invoke mqttwarn with the corresponding --config-file option.

docker run --rm -it --network=host --volume=$PWD:/etc/mqttwarn \
  ghcr.io/jpmens/mqttwarn-standard \
  mqttwarn --config-file=mqttwarn-owntracks.ini

Running ntfy as container

While this tutorial uses the ntfy service at ntfy.sh, it is possible to run your own instance. For example, use Docker or Podman.

docker run --name=ntfy --rm -it --publish=5555:80 \
  binwiederhier/ntfy serve --base-url="http://localhost:5555"

In this case, please adjust the ntfy configuration section [config:ntfy] to use a different URL, and make sure to restart mqttwarn afterwards.

[config:ntfy]
targets   = {'testdrive': 'http://localhost:5555/testdrive'}

Alternative languages for user-defined functions

JavaScript

In order to explore JavaScript user-defined functions using the OwnTracks-to-ntfy recipe, use the alternative mqttwarn-owntracks.js implementation by adjusting the functions setting within the [defaults] section of your configuration file, and restart mqttwarn.

[defaults]
functions = mqttwarn-owntracks.js

The JavaScript function owntracks_batteryfilter() implements the same rule as the previous one, which was written in Python.

/**
 *
 * Forward OwnTracks low-battery warnings to ntfy.
 * https://mqttwarn.readthedocs.io/en/latest/examples/owntracks-battery/readme.html
 *
 */

// mqttwarn filter function, returning true if the message should be ignored.
// In this case, ignore all battery level telemetry values above a certain threshold.
function owntracks_batteryfilter(topic, message) {
    let ignore = true;
    let data;

    // Decode inbound message.
    try {
        data = JSON.parse(message);
    } catch {
        data = null;
    }

    // Evaluate filtering rule.
    if (data && "batt" in data && data.batt !== null) {
        ignore = Number.parseFloat(data.batt) > 20;
    }

    return ignore;
}

// Status message.
console.log("Loaded JavaScript module.");

// Export symbols.
module.exports = {
    "owntracks_batteryfilter": owntracks_batteryfilter,
};

Attention

The feature to run JavaScript code is currently considered to be experimental. Please use it responsibly.

Lua

In order to explore Lua user-defined functions using the OwnTracks-to-ntfy recipe, use the alternative mqttwarn-owntracks.lua implementation by adjusting the functions setting within the [defaults] section of your configuration file, and restart mqttwarn.

[defaults]
functions = mqttwarn-owntracks.lua

The Lua function owntracks_batteryfilter() implements the same rule as the previous ones, which was written in Python and JavaScript.

--[[
Forward OwnTracks low-battery warnings to ntfy.
https://mqttwarn.readthedocs.io/en/latest/examples/owntracks-battery/readme.html
--]]

-- mqttwarn filter function, returning true if the message should be ignored.
-- In this case, ignore all battery level telemetry values above a certain threshold.
function owntracks_batteryfilter(topic, message)
    local ignore = true

    -- Decode inbound message.
    local data = json.decode(message)

    -- Evaluate filtering rule.
    if data ~= nil and data.batt ~= nil then
        ignore = tonumber(data.batt) > 20
    end

    return ignore
end

-- Status message.
print("Loaded Lua module.")

-- Export symbols.
return {
    owntracks_batteryfilter = owntracks_batteryfilter,
}

Attention

The feature to run Lua code is currently considered to be experimental. Please use it responsibly.