OSGi Integration within OpenNMS

OpenNMS uses OSGi framework in a Karaf Container.

This document explains how to integrate a Maven module (OSGi bundle) into the system.

Add a new Maven module

This section describes how to integrate a new Maven module into OpenNMS.

Any new Maven module that we need to add to OpennMS is mostly a bundle (jar + OSGi metadata).

After creating a Maven module, add the following plugin to pom.xml to create the necessary OSGi metadata.


                    <!-- <Export-Package>org.foo.myproject.api</Export-Package>--> (1)
                    <!-- <Import-Package>org.foo.myproject.api.dependencies</Import-Package>--> (2)
                    <!-- <Private-Package>org.foo.myproject.impl</Private-Package>--> (3)
                    <!-- <Karaf-Commands>*</Karaf-Commands>-->                      (4)
1 Can define packages that can be exported here; optional not needed by default.
2 Can import packages from dependent modules; optional not needed by default.
3 Private packages that should not be exported; optional not needed by default.
4 Add this when the module is for adding Karaf commands (needed only for Karaf command bundles).

Adding a Karaf feature

A feature is a combination of bundles that can be installed in Karaf. For a given module, all the dependencies need to be specified in feature. Sometimes there are run time dependencies that will trigger only when you actually do something in the feature.

Example feature
   <feature name="scv-api" version="${project.version}" description="Secure Credentials Vault">
    <feature name="scv-jceks-impl" version="${project.version}" description="Secure Credentials Vault JCEKS Impl">
        <bundle dependency="true">mvn:commons-codec/commons-codec/${commonsCodecVersion}</bundle>
        <bundle dependency="true">mvn:com.google.guava/guava/${guavaVersion}</bundle>

Feature definitions

You can define the features in following feature files, located in container/features/src/main/resources/

  • features.xml - All the features specific to OpenNMS and common to Minion/Sentinel.

  • features-minion.xml - All the features that are specific to Minion.

  • features-sentinel.xml - All the features that are specific to Sentinel.

Make new feature available on Karaf Container.

  • OpenNMS: add the feature in opennms-full-assembly/pom.xml.

  • Minion: add this feature and Maven dependencies in features/minion/repository/pom.xml.

  • Sentinel: add this feature and Maven dependencies in features/sentinel/repository/pom.xml.

Install a new feature by default

  • OpenNMS: add the feature in container/karaf/src/main/filtered-resources/etc/org.apache.karaf.features.cfg.

  • Minion: add the feature in features/minion/repository/src/main/resources/features.boot.

  • Sentinel: add this feature in features/container/sentinel/src/main/filtered-resources/etc/org.apache.karaf.features.cfg.

Modules that need to be on Spring

If a Maven module should be loaded in Spring by default, that Maven module should be included in opennms-base-assembly/pom.xml. All the modules that are loaded in Spring will be available in ${opennms.target}/opennms/lib.

Some modules are only defined in Spring (legacy, RPC modules like opennms-services). These are loaded in Default ClassLoader.

Add Spring beans to the OSGi service registry by exposing the bean as <onmsgi:service>.

When to add a package to custom.properties

Packages added to custom.properties are loaded in the default classloader even when loaded in OSGi. You must use custom.properties to export packages that are loaded in Spring but also accessed through OSGi.

Health Check

Health Check is available on all Karaf containers. Health Check validates whether all features are enabled.


If you see any failure related to a bundle, you can do bundle:diag id to understand the specific failure.

Reload a specific Maven module dynamically for debugging

bundle:watch *

bundle:watch~ in the Karaf container, watches any updates in the local m2 repository. Do mvn clean install in a specific module to update it in the local Karaf repository.

Avoid host key checking for Karaf SSH

Add the following lines to .ssh/config

Host localhost
    HostKeyAlgorithms +ssh-dss
    StrictHostKeyChecking no