Java-based open-source message broker supported by the Apache community. (See Set Up Message Broker.)


The Architecture for Learning Enabled Correlation (ALEC) is an OpenNMS framework that uses artificial intelligence and machine learning to provide alarm triage. ALEC groups related alarms so you can better manage the more complex situations they might represent.

Application Perspective Monitoring (APM)

A method that uses the Minion infrastructure to monitor a service’s availability from different perspectives to help identify if nodes are down for everyone or if an outage affects only certain sites. When a service is not responsive an outage will be generated with the corresponding perspective that sees the outage. (See Application Perspective Monitoring.)


Open-source distributed/scale-out NoSQL database designed to hold large amounts of structured or unstructured data across many servers. (See Newts.)


A process that uses ICMP to find network devices and services in your network and then automatically adds them to monitoring. (See Provisioning.)


The service on an OpenNMS core that controls the operation of Minions. (See Configuring Minion via Confd.)


Elasticsearch is a search engine based on the Lucene library. OpenNMS persists/forwards certain data to Elasticsearch to store flow records and warehouse events and alarm history for long-term storage of this data. (See Elasticsearch Integration.)


Helm is an an OpenNMS application for creating flexible dashboards to display and customize fault management and performance management data from Horizon and Meridian. Helm works with the Grafana analytics program to customize the data you can view.


Open-source solution from OpenNMS that helps users visualize and monitor everything on their local and remote networks. Free, community-driven project includes the latest technology and features delivered through a rapid release cycle.


If This Then That (IFTTT) service integrates apps, devices, and services. Horizon and Meridian can integrate with IFTTT to trigger actions on other services based on customized alarms. (See IFTTT Integration.)


JRobin is a clone of RRDTool (see below) written in Java. Default time series database for new Meridian instances.


Clusterable, open-source message broker designed for high-throughput/low-latency event streaming originally developed at LinkedIn, now supported by the Apache community. (See Set Up Message Broker.)

KSC Reports

Key SNMP customized (KSC) reports provide a way to generate prefabricated graphical views of collected data. They let you display data from different devices and sources (SNMP, ICMP, HTTP) on one page. (See KSC Reports.)


Subscription-based, optimized, and stable version of the OpenNMS Horizon platform. Annual release with monthly security patches that includes only the most stable and secure Horizon features.

Message broker

When using Minions and Sentinels, a message broker is required for communication between servers. Meridian has an embedded ActiveMQ server available for smaller deployments. You can swap the broker with a dedicated ActiveMQ, gRPC, or Kafaka cluster to provide scalability and load balancing.


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. (See Minion.)


OpenNMS component that enables horizontal scaling of flow processing. Not required for flow processing, but can improve performance for deployments with a very high volume of flow documents.


Newts (New-Fangled Time Series Datastore) is an OpenNMS time series data store based on Apache Cassandra. Use it as an alternative persistence strategy instead of JRobin or RRDtool. (See Newts.)

Operator board

Customizable dashboard to visualize monitoring information. (See Operator Board.)


Commonly used open-source relational database known for its stability. PostgreSQL scales up but not out. (See Set up PostgreSQL.)


PRovisioning Integration Server, an optional service to gather node inventory information from an external source. Use to generate requisition XML files for creating/updating/removing nodes for monitoring.


The process of getting your devices, applications, and services into monitoring. (See Provisioning.)

Remote Method Invocation (RMI)

Java API that lets one Java Virtual Machine (JVM) running object to invoke methods on an object running in another JVM. RMI integration lets you access Horizon/Meridian through jconsole or remote manage them. (See Enabling RMI.)

Round Robin Database (RRD)

Special type of database designed for collection, visualization, and analysis of time-series data. Data is maintained as a fixed-size circular-buffer that overwrites the oldest data with new data.


Karaf container that provides scalability for data processing, including flows, SNMP traps, syslog messages, and streaming telemetry in OpenNMS. It also supports thresholding for streaming telemetry if you are using OpenNMS Newts. (See Sentinel.)

Time series, time-series database (TSDB)

Time series is a sequence of data points that occur in successive order over a period of time. A time series database (TSDB) is designed to store and serve time series data. (See Time Series Storage and time series database.)