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🐳 Core and Web application service for Horizon by OpenNMS
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assets Resolve #39: Added OPENNMS_DBNAME variable to opennms-datasources.xml… Sep 27, 2018
LICENSE Fix master to be latest stable [ci skip] Apr 11, 2019
docker-compose.yml Fixing logic to remove validating user at runtime. Mar 11, 2019
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opennms-helm.yml Set to version bleeding for master Jul 19, 2018

Docker Image for OpenNMS Horizon

Version Tags

  • bleeding, daily bleeding edge version of Horizon 24 using OpenJDK 8u191-jdk
  • 23.0.4-1, latest is a reference to last stable release of Horizon using OpenJDK 8u191-jdk

General Project Information

Horizon Docker files

This repository provides snapshots for Horizon as docker images. The image provides the Horizon core monitoring services and the web application.

It is recommended to use docker-compose to build a service stack using the official PostgreSQL image. In case you have already a PostgreSQL database running, you can provide the database configuration in the .opennms.env and .postgres.env environment files, otherwise users and database will be created.

Data is by default persisted on your Docker host using a local volume driver for the following data:

# PostgreSQL database
  driver: local

# OpenNMS Horizon RRD files, logs and generated PDF reports
  driver: local

# OpenNMS Horizon configuration files
  driver: local

It is required to manually edit OpenNMS Horizon configuration files, you can add your own configuration files by providing a etc-overlay directory. On startup the files overwrite the default configuration.

- ./etc-overlay:/opt/opennms-etc-overlay

If you prefer to have you OpenNMS Horizon configuration on your Docker host in a specific directory, you can mount a directory with your config like this:

    - ./myHorizonConfig:/opt/opennms/etc

In case the directory is empty, it will be initialized with a default pristine configuration from /opt/opennms/share/etc-pristine.

IMPORTANT: Take care about configurations which can be changed through the Web UI which are persisted on the file system, e.g. users.xml, groups.xml, surveillance-categories.xml, snmp-config.xml, etc.


  • docker in a current stable version
  • docker-compose in a current stable version
  • git


git clone
cd docker-horizon-core-web
docker-compose up -d

The web application is exposed on TCP port 8980. You can login with default user admin with password admin. Please change immediately the default password to a secure password.

To get a help for all available container options just run:

docker run --rm opennms/horizon-core-web

Set Java Options

It is easily possible to add Java options to control the behavior of the JVM for performance tuning or debugging. The environment variable JAVA_OPTS is passed on the Java command and can be used to extend or overwrite JVM options.

IMPORTANT: To give more control the Java binary command natively in the and Java options in opennms.conf are not evaluated. The java process has PID 1 and

Used in an environment file:

  - .java.env

cat .java.env
JAVA_OPTS=-XX:+UseParallelGC -XX:+PrintGCDetails -XX:+PrintFlagsFinal

Used in docker-compose service environment definition:

  container_name: opennms.core.web
  image: opennms/horizon-core-web:latest
    - JAVA_OPTS=-XX:+UseParallelGC -XX:+PrintGCDetails -XX:+PrintFlagsFinal

Java and Container Heap Memory

To control and isolate resource usage of processes the Kernel feature cgroups (Control Groups) is used. With the combination of Java there are some additional things to take care of regarding the Maximum Heap Size and limiting memory usage of the container.

By default JVM ergonomics calculates the Maximum Heaps Size based on the Docker host memory and not by the memory set with with cgroups.

To ensure the JVM calculates the Maximum Heap Size correct you have two options:

  1. Set the correct Maximum Heap Size manually with -Xmx see section above Set Java Options
  2. If no -Xmx option is set, you can automatically calculate the Maximum Heap Size with enabling the experimental cgroup aware feature with
JAVA_OPTS=-XX:+UnlockExperimentalVMOptions -XX:+UseCGroupMemoryLimitForHeap

As of Java SE 8u131 the JVM is Docker-aware with Docker CPU limits transparently. As long if -XX:ParallelGCThreads or -XX:CICompilerCount are not specified, the JVM will apply the Docker CPU limit as the number CPUs and calculates the number of GC and JIT compiler threads just like running on bare metal.

Update and Maintenance

The entry point script is used to control starting behavior:

-f: Apply overlay configuration if exist and just start OpenNMS Horizon
-h: Show help
-i: If necessary initialize database, create pristine configuration, do an upgrade and apply the overlay config but do *not* start OpenNMS Horizon
-s: Same as -i but start OpenNMS Horizon, this should be your default
-n: Initialize Newts on Cassandra and the PostgreSQL database, do *not* start OpenNMS Horizon
-c: Same as -n but start OpenNMS Horizon, this should be your default when you want to use Newts on Cassandra
-t: Just test you configuration

If you want to enforce an update, create a /opt/opennms/etc/do-upgrade file. Starting with -i or -s will run the install -dis command once to update the configuration and database schema.

All options which do upgrades or start OpenNMS Horizon verify if the configuration is valid and pass the configuration test.

Using etc-overlay for custom configuration

If you just want to maintain custom configuration files outside of OpenNMS, you can use an etc-overlay directory. All files in this directory are just copied into /opt/opennms/etc in the running container. You can just mount a local directory like this:

  - ./etc-overlay:/opt/opennms-etc-overlay

Using jetty-overlay to customize Jetty WEBINF

If you just want to maintain custom configuration files for the Jetty application container, you can use an jetty-overlay directory. All files in this directory are just copied into /opt/opennms/jetty-webapps/opennms/WEB-INF in the running container. You can just mount a local directory like this:

  - ./jetty-overlay:/opt/opennms-jetty-webinf-overlay

Using overlay for custom arbitrary configuration

To overlay arbitrary configuration files/directory structures, you can use an opennms-overlay directory. The contents of this directory are copied into /opt/opennms/ in the running container. You can just mount a local directory like this:

  - ./opennms-overlay:/opt/opennms-overlay

Test configuration files

This image allows to test configuration files if they are valid XML and if they can be loaded on startup. It is automatically executed on startup but can also it can just be executed as a single shot command.

Get the usage output of the config tester with:

docker run --rm opennms/horizon-core-web:latest -t

Some examples how to use the config tester with this image:

Test all configuration files:

docker run --rm opennms/horizon-core-web:latest -t -a

Test just a specific configuration file with verbose output -v:

docker run --rm opennms/horizon-core-web:latest -t -v snmp-config.xml

Test configuration files with a etc-overlay directory:

docker run --rm -v $(pwd)/etc-overlay:/opt/opennms-etc-overlay opennms/horizon-core-web:latest -t -v snmp-config.xml

Environment Variables

  • POSTGRES_HOST: PostgreSQL database host, default: database
  • POSTGRES_PORT: Port to access PostgreSQL database, default: 5432
  • POSTGRES_USER: PostgreSQL admin user, default: postgres
  • POSTGRES_PASSWORD: PostgreSQL admin password, default: postgres
  • OPENNMS_DBNAME: Database name for OpenNMS Horizon, default: opennms
  • OPENNMS_DBUSER: User to access the OpenNMS Horizon database, default: opennms
  • OPENNMS_DBPASS: Password for OpenNMS Horizon database user, default: opennms
  • OPENNMS_KARAF_SSH_HOST: Listening address for Karaf SSH port, default:
  • OPENNMS_KARAF_SSH_PORT: SSH port for Karaf, default: 8101

Using a Cassandra Cluster:

  • ${OPENNMS_CASSANDRA_HOSTNAMES}: Host name or IP address of the cassandra cluster, a comma separated list is also accepts
  • ${OPENNMS_CASSANDRA_KEYSPACE}: Name space to persist performance data in, default: newts
  • ${OPENNMS_CASSANDRA_PORT}: Cassandra port, default: 9042
  • ${OPENNMS_CASSANDRA_USERNAME}: User name accessing Cassandra
  • ${OPENNMS_CASSANDRA_PASSWORD}: Password accessing Cassandra

Running on Cassandra with Newts

By default the OpenNMS Horizon image will run using RRDTool for performance data storage. However OpenNMS Horizon can also be configured to run on Cassandra using the Newts time series schema.

The configuration options can be found in the Environment Variables section. The opennms-cassandra-helm.yml is provided which illustrates how to run OpenNMS Horizon with a small single Cassandra node on the same machine.

Build Argument

  • MIRROR_HOST: Server with RPM packages, default:
  • OPENNMS_VERSION: Version of OpenNMS Horizon RPM files, default: stable
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