A Minion is an instance of the Karaf OSGi service that enables OpenNMS to monitor devices and services in locations that OpenNMS cannot reach. Minions communicate with these remote devices while OpenNMS performs coordination and task delegation.

Minions can operate behind a firewall and/or network address translation (NAT) as long as they can communicate with OpenNMS via an ActiveMQ or Apache Kafka message broker.

Using Minions to monitor devices and services in hard-to-reach, remote network locations:

  • means you do not have to set up and maintain a large set of firewall rules for multiple mangement protocols

  • avoids the difficulty of communicating with managed devices over unreliable networks, using UDP-based management protocols

  • simplifies the network communication to the message broker and REST endpoint

How it Works

A Minion monitors all the managed nodes and IP services in the same location (e.g., Pittsboro office, building_3). The Minion communicates with the message broker, which in turn communicates with the OpenNMS instance.

Figure 1. Nodes with Minions in locations

By default, every node provisioned in Meridian is created in the "Default" location. The central Meridian instance itself handles all nodes and services in the "Default" location. To enable the Minion to handle all the nodes and services in a remote location, you define that location (e.g., Pittsboro office, building_3), and set the Miniion’s location configuration property to that location. The Minion registers itself to the Meridian instance on startup.

Meridian’s' provisioning system lets you associate nodes with any location. Meridian delegates monitoring requests for nodes in a specified location to the Minion(s) configured for that location, using the Minion as a proxy.

Figure Minion communication provides a more detailed overview about the communication between a Meridian instance and a Minion.

Figure 2. Minion communication

By default the Minion is automatically provisioned as a node in the Meridian instance and automatically monitored with the Minion-Heartbeat service. The Minion sends heartbeat messages to ensure it is running and functioning properly in this location.

The specific management protocol messages (e.g., SNMP, ICMP), are piped through a message broker communication channel and are executed by a Minion. The broker forwards responses to the central Meridian instance, which processes them accordingly.

The following management protocols are currently supported in a Minion proxy scenario:

  • Receive Syslog messages and SNMP traps and forward them through the message broker to a central Meridian instance

  • Act as a proxy for SNMP performance data collection

  • Act as a proxy for service monitors to test availability and measure response times from applications