What’s New

System Requirements

  • Java 8 through 11: OpenNMS Meridian 2021 runs on JDK 8 through 11. We recommend the most recent version of OpenJDK 11.

  • PostgreSQL 10 or higher: Meridian 2021 requires any supported version of PostgreSQL from 10 up to (and including) 13.

Breaking Changes

Kafka RPC Enables single topic configuration by default.

Enables single topic by default for Kafka RPC which would reduce number of topics on Kafka. Both Minion and OpenNMS need to be updated to OpenNMS Meridian 2021. Make sure that Kafka Lag on Sink topics be minimal before upgrading otherwise there may be loss of those sink messages.

Situation Feedback Persistence Configuration

The configuration file etc/org.opennms.features.situation-feedback.persistence.elastic.cfg has been renamed to etc/org.opennms.features.situationfeedback.persistence.elastic.cfg, i.e. the minus sign is removed from the filename. This is to work around an initialization bug where Karaf treated configuration files with dashes in a special manner.

Remote Poller Removed

The remote poller has been removed from Meridian 2021. It has been replaced with new infrastructure for perspective-based monitoring that runs on Minions.

VMware Assets

VMware-related data is not longer stored in node assets. The install command will move any existing VMware asset data to the node’s metadata when you upgrade.

New Features and Improvements

Karaf Shell

A number of useful commands have been added or updated in the Karaf shell.

  • alarm-list: list current alarms (optionally filtered by UEI)

  • event-list: list events (optionally filtered by UEI)

  • ip-addr-range: generate a list of IP addresses to use in other commands

  • reload-daemon: now accepts an optional configuration file to target for reload

  • send-event: additional options supported to match the CLI version of send-event more closely

  • snmp-fit: can now optionally send a newSuspect event on success

  • snmp-get: like snmp-walk, but fetches a single MIB object and prints the result

Minion and Sentinel

  • The Minion confd configuration support now handles a bunch more options, including setting Jetty, RMI, and ssh host and port, Secure Credentials Vault configuration, and environment variables and options for the JVM. For details, see the CONFD_README file.

  • It’s now possible to override entries in a Sentinel’s system.properties with a file called custom.system.properties

Application Perspective Monitoring

Application Perspective Monitoring replaces the old Remote Poller.

It uses the Minion infrastructure to monitor a service’s availability from these different perspectives. When a service is not responsive an outage will be generated with the corresponding perspective.

A number of provisioning, polling, and web UI changes have been made to accomodate this new infrastructure.


  • Node scan has been updated to limit the number of concurrent RPC requests so as not to overload communication with Minions.

  • New policies have been added for creating node and interface metadata during provisioning.

Polling and Monitoring

  • WMI/SMB support has been updated to use a wider set of encryption types.

  • Data collection configuration has been added for Netscaler vServer.


  • It is now possible to use metadata in threshold evaluation.

RPC, Telemetry, Flows, and BMP

  • Improvements have been made for supporting aggregate flow metrics.

  • Flow DNS enrichment has been enhanced to improve performance.

  • Aggregate flow queries now support resolving hostnames if available.

  • Sink RPC APIs have been enhanced to expose metrics to Karaf for tracing and performance tuning.

  • The OpenConfig integration now supports gNMI, in addition to JTI.

  • The OpenConfig integration also supports collection from OpenConfig over the gRPC JTI — this was introduced in Horizon 26.2.0 after Meridian 2020 was branched.


  • It is now possible to use node-, interface-, and service-level metadata in notifications.


  • Events for applicationCreated/applicationDeleted are now sent when applications are added or removed through the ReST API.

  • A new v2 API for retrieving application status has been added.

Web UI Improvements

  • A new universal search bar has been added which allows for searching alarms, nodes, and more from the top of any page in the UI.

Documentation Updates

Documentation improvements and additions have been made in a number of areas:

  • Application Perspective Monitoring

  • Data Collection Configuration

  • Metadata

  • Mail Transport Monitor

  • Minion/Kafka RPC Tuning

  • Thresholding

  • Users Configuration, Duty Schedules, and Security Roles

…​plus TONS of smaller readability improvements.

Kafka Producer Metrics

  • For Interface Resources, a String attribute named __ifIndex is added to represent missing Interface ifIndex in String form.

Important Internal Changes

  • Sink internals have been updated to use Protobuf 3.

Other Improvements

Since Meridian 2021 is based on Horizon 27.1, it contains all the fixes and updates that have occurred since Meridian 2020 was created from the Horizon 26 codebase.

For a more complete list of major changes included in this release, see the "What’s New" documentation for Horizon 27.1.1.