Newts

Newts is a time series data schema for Apache Cassandra. It enables horizontal scaling for your time series database and is an alternative to RRDtool.

Newts and its Apache Cassandra backend should be considered deprecated. Meridian 2026 still ships with Newts support for existing Newts users: if you are already running on Newts, you can continue to do so through this release.

After Meridian 2026 reaches end of support, OpenNMS will no longer provide official support for the Cassandra backend, and Newts will not be carried forward into subsequent releases. For new deployments, and when planning an upgrade path for an existing one, we suggest looking at the Prometheus RemoteWrite plugin, which stores metrics in any Prometheus remote_write-compatible time series database. Note that there is no tool to copy existing Newts data into another store, so after a switch the historical metrics remain in Cassandra until its retention period expires.

This section describes how to configure Meridian to use an existing Cassandra cluster, including how to initialize the Newts keyspace using newts init with STCS without production-ready tuning, and verify that time series data is stored and can be accessed

It also provides reference documentation for Newts:

Cassandra documentation

Cassandra cluster design, setup, sizing, tuning, and operation are out of scope for this documentation. To install and set up a Cassandra cluster, please follow the Cassandra installation instructions. For further information, see Cassandra Getting Started Guide.

To avoid unwanted updates, disable the Cassandra repository on DNF/YUM-based distributions or use apt-mark hold cassandra on APT based distributions.
For simplicity we use the ${OPENNMS_HOME}/bin/newts init command which initializes a Newts keyspace for you and the defaults are not optimally tuned for a production-ready environment. To build a production environment please consult Sizing Cassandra for Newts and planning anti-patterns in Cassandra.

Before you begin

Make sure you have the following:

  • A running instance of Meridian running on Linux

  • Working data collection and response time metrics from collectd and pollerd

  • Cassandra cluster with access to the Cassandra client port 9042/tcp

Note that you must make configurations in the etc directory relative to the Meridian Core home directory. Depending on your operating system, the home directory is /opt/opennms for Debian/Ubuntu and for CentOS/RHEL.