MQTT Monitoring with PRTG

MQTT (Message Queuing Telemetry Transport) is a lightweight messaging protocol. It is used in cases where a small code footprint is needed while bandwidth resources are limited. It is primarily used for machine-to-machine (M2M) communication or Internet of Things types of MQTT connections. MQTT 5 is the latest version of the MQTT protocol.

MQTT supports different levels of QoS and Last Will and Testament (LWT). It can use SSL/TLS to secure the communication channel between the client and the broker. MQTT also supports various authentication mechanisms (username/password, tokens) and can enforce authorization policies to control access to topics.

Devices send MQTT messages to each other via:

• Topics: These are a way of categorizing the types of messages that are sent. If a sensor measures temperature, for example, the topic can be defined as “TEMP”, and the sensor sends messages out labelled as “TEMP”.
• Publishers: Devices can be configured to send out messages containing data. Using the temperature example, the sensor measuring temperature publishes this data.
• Subscribers: Devices or systems can be configured to receive only messages of a specific topic. They can also have subscriptions of multiple topics.
• Broker: This is the server that is at the center of MQTT communication. It transmits the published messages to servers or MQTT clients that have subscribed to specific topics. An example is the open-source message broker Mosquitto.

MQTT monitoring involves overseeing the performance, reliability, and security of MQTT-based messaging systems. This includes tracking the behavior of MQTT brokers, clients, and the overall message flow within the system. Effective monitoring ensures the health and efficiency of MQTT deployments, particularly in mission-critical applications such as IoT.

Use cases of MQTT monitoring include:

• Broker monitoring:
  • Connection status: Track the status of client connections, including successful connections, disconnections, and reconnections.
  • Message throughput: Monitor the rate of messages being published and delivered.
  • Resource usage: Keep an eye on CPU, memory, and network usage of the broker to prevent overload and ensure scalability.
  • Error rates: Monitor error logs and rates to detect issues like failed receiving messages or authentication errors.
• Client monitoring:
  • Connection quality: Track connection stability, including connection duration and frequency of reconnections.
  • Message latency: Measure the time it takes for messages to be delivered from publishers to subscribers.
• Message flow monitoring:
  • Topic usage: Monitor which topics are being used, how frequently they are published to or subscribed to, and the size of the messages.
  • QoS levels: Track the usage and performance of different Quality of Service levels.
  • Retained messages: Monitor the state and delivery of retained messages.

Paessler PRTG is a comprehensive monitoring tool that supports a wide range of industrial standards and protocols to monitor various aspects of industrial IT infrastructure, including:

• Modbus TCP
• OPC UA (Open Platform Communications Unified Architecture)
• IPMI and Redfish

It also comes with preconfigured sensor types for manufacturers such as Rittal or Beckhoff.

In PRTG, “sensors” are the basic monitoring elements. One sensor usually monitors one measured value in your network, for example the traffic of a switch port, the CPU load of a server, or the free space on a disk drive. On average, you need about 5-10 sensors per device or one sensor per switch port.