MQTT Monitoring

A lightweight Scala service for monitoring MQTT topics and exporting numeric values (including JSON extraction) to OpenTelemetry metrics.

• Connects to MQTT v3 brokers
• Subscribes to user-defined topic patterns (with support for +, #, and custom JSON selectors like #>)
• Parses and extracts numeric values from plain text or JSON payloads
• Applies regex-based value mappings and label extraction
• Supports OpenTelemetry gauge metric exporting
• Optional array support for JSON lists
• Configurable via a single JSON environment variable (CONFIG)
• Graceful shutdown and batching support

{
  "server": "localhost:1883",
  "username": "user",
  "password": "secret",
  "filters": [
    {
      "metric": "mqtt.value",
      "topics": [
        "sensors/+/temp",
        "devices/#",
        "home/lights/#>/state/value"
      ],
      "labelPatterns": [
        "sensors/(?<device>[^/]+)/(?<type>[^/]+)",
        "devices/(?<id>[^/]+)"
      ],
      "valueMappings": {
        "on": "1",
        "off": "0",
        "yes": "1",
        "no": "0",
        "val=(.*)": "$1"
      },
      "enableArrays": true
    }
  ]
}

• JVM 17+
• MQTT broker (e.g., Mosquitto)
• OpenTelemetry-compatible backend (e.g., Prometheus, OTLP Collector)

export CONFIG='{"server": "...", ...}'  # Or load from file and export
java -jar mqtt-monitoring.jar

Logs will show connection, subscriptions, received values, and metric exports.

This service uses the OpenTelemetry Java SDK to send gauge metrics. You can configure the export pipeline via standard OTel environment variables (e.g., OTEL_EXPORTER_OTLP_ENDPOINT).

sbt assembly

sbt test

This project uses the Apache 2.0 License. See the file called LICENSE.