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.

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

  • no need to set up and maintain a large set of firewall rules for multiple management protocols

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

  • simplify 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 (for example, 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 a location (for example, "Pittsboro office, building-3") in your core server, and configure the location property on the Minion to match. The Minion registers itself to the Meridian instance on start-up.

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.

The following provides a more detailed overview of the communication between a Meridian instance and a Minion:

Figure 2. Minion communication

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

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

A Minion proxy scenario supports the following management protocols:

  • 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