ups-json-publisher

UPS Data Publisher for MQTT: Capture UPS details using upsc, format as JSON, and send to MQTT broker.

• ups-json-publisher
  • Usage
    • Clone the Repository
    • Configure MQTT Broker Settings
    • Run the Script
    • Run the Script Periodically with Cron
  • Node-RED transformation and InfluxDB import
  • License

Usage

Clone the Repository

git clone https://github.com/filipnet/ups-json-publisher.git
cd ups-json-publisher

Configure MQTT Broker Settings

Copy the example configuration file:

cp config.sh.example config.sh

Open config.sh in a text editor (e.g., nano, vim) and replace placeholders with your actual MQTT broker information.

Run the Script

Make sure the required dependencies are installed: upsc (part of Network UPS Tools) and mosquitto_pub (part of Mosquitto MQTT client).

Run the script with the device name as an argument:

./mqtt_upsc_script.sh <device_name>

Important: Protect Your Configuration:

The config.sh file contains sensitive information. Make sure not to expose your credentials by adding config.sh to the .gitignore file. Never commit the actual config.sh to the repository.

Run the Script Periodically with Cron

To run the script periodically, you can add a line to the system-wide crontab file. Open the crontab configuration:

sudo vim /etc/crontab

Add the following line to run the script every 5 seconds, suppressing the script output:

*/5 * * * * /bin/timeout -s 2 1m /root/ups-json-publisher/mqtt_upsc_script.sh <device name> >/dev/null 2>&1

For shorter time intervals you can also use the helper-script "run_upsc_script.sh".

Replace <device_name> with the actual name of your UPS device.

If the execution intervals are too short, the script may be restarted before the previous process has finished - which can lead to problems with system performance or the MQTT server. Therefore, always adjust the timeout in the cronjob to a value below the set execution interval.

• Mosquitto MQTT Client

Node-RED transformation and InfluxDB import

If the scheduler and an MQTT input node have been configured, all data from the output of nutc should now arrive in the node-RED. Forwarding this data to InfluxDB is simple due to the JSON format. Since InfluxDB is a time series database it makes sense to pass the fields that have a numeric value to InfluxDB as a number and not as a string. For this I wrote a separate function.

Die Funktionion sieht dabei wie folgt aus:

// Node-RED Function Node
// Processes JSON input and returns a JSON differentiating between Strings and Numbers

var inputJSON = msg.payload;

function differentiateJSON(inputJSON) {
    var outputJSON = {};

    for (var key in inputJSON) {
        if (/^-?\d*\.?\d+$/.test(inputJSON[key])) {
            outputJSON[key] = parseFloat(inputJSON[key]); // Convert value to Number
        } else {
            outputJSON[key] = inputJSON[key];
        }
    }

    return outputJSON;
}

var outputJSON = differentiateJSON(inputJSON);
msg.payload = outputJSON;

return msg;

To pass only certain values to InfluxDB, a downstream function node can be used that might look like this:

var inputJson = msg.payload; // Input JSON

// Select desired keys/values
/*
    battery.charge = Battery charge (percent)
    battery.runtime = Battery runtime (seconds)
    ups.realpower = Current value of real power (Watts)
*/
var desiredKeys = ["battery.charge", "battery.runtime", "ups.realpower"]; // Specify the desired keys here

var outputJson = {};

for (var i = 0; i < desiredKeys.length; i++) {
    var key = desiredKeys[i];
    if (inputJson.hasOwnProperty(key)) {
        outputJson[key] = inputJson[key];
    }
}

msg.payload = outputJson; // Set the output
return msg;

License

This project is licensed under the BSD 3-Clause License.