Tuning ActiveMQ

The settings for the embedded ActiveMQ broker are found in ${OPENNMS_HOME}/etc/opennms-activemq.xml. Memory and storage limits are conservative by default and should be tuned to accommodate your workload. Consider increasing the memoryUsage (defaults to 20MB) to 512MB or greater, assuming you have enough heap available.

If the memory limit is reached, flow control will prevent messages from being published to the broker.

Monitoring the ActiveMQ broker using the Karaf shell

Use the opennms:activemq-stats command available via the Karaf shell to show statistics about the embedded broker:

If the command is not available, try installing the feature using feature:install opennms-activemq-shell

This command reports some high level broker statistics as well as message, enqueue and dequeue counts for the available queues. Pay close attention to the memory usage that is reported. If the usage is high, use the queue statistics to help isolate which queue is consuming most of the memory.

The opennms:activemq-purge-queue command can be used to delete all of the available messages in a particular queue:

opennms:activemq-purge-queue OpenNMS.Sink.Trap

Authentication and authorization with ActiveMQ

The embedded ActiveMQ broker is preconfigured to authenticate clients using the same authentication mechanisms (JAAS) as the Horizon web application.

Users associated with the ADMIN role can read, write or create any queue or topic.

Users associated with the MINION role are restricted in such a way that prevents them from making RPC requests to other locations, but can otherwise read or write to the queues they need.

See the authorizationPlugin section in ${OPENNMS_HOME}/etc/opennms-activemq.xml for details.

Multi-tenancy with Horizon and ActiveMQ

The queue names Horizon uses are prefixed with a constant value. If many Horizon are configured to use the same broker, then these queues would end up being shared among the instances, which is not desired. In order to isolate multiple instances on the same broker, you can customize the prefix by setting the value of the org.opennms.instance.id system property to something that is unique per instance.


Update the Minion’s instance ID accordingly to match the Horizon instance.

If you change the instance ID setting when using the embedded broker, you will need to update the authorization section in the broker’s configuration to reflect the updated prefix. Modify the configuration with the file ${OPENNMS_HOME}/etc/opennms-activemq.xml:
        <!-- Users in the admin role can read/write/create any queue/topic -->
        <authorizationEntry queue=">" read="admin" write="admin" admin="admin" />
        <authorizationEntry topic=">" read="admin" write="admin" admin="admin"/>
        <!-- Users in the minion role can write/create queues that are not keyed by location -->
        <authorizationEntry queue="<YOUR INSTANCE ID>.*.*" write="minion" admin="minion" />
        <!-- Users in the minion role can read/create from queues that are keyed by location -->
        <authorizationEntry queue="<YOUR INSTANCE ID>.*.*.*" read="minion" admin="minion" />
        <!-- Users in the minion role can read/write/create advisory topics -->
        <authorizationEntry topic="ActiveMQ.Advisory.>" read="minion" write="minion" admin="minion"/>
      <!-- Allow all users to read/write/create temporary destinations (by omitting a <tempDestinationAuthorizationEntry>) -->

Tuning the RPC client in OpenNMS

The following system properties can be used to tune the thread pool used to issue RPCs:

Name Default Description



Number of threads which are always active.



Maximum number of threads which can be active. These will exit after remaining unused for some period of time.



Maximum number of requests to queue. Set to -1 to be unlimited.

Use the opennms:stress-rpc Karaf shell command to help evaluate and tune performance.

Troubleshooting RPC failures

Symptoms of RPC failures may include missed polls, missed data collection attempts and the inability to provision or re-scan existing nodes. For these reasons, it is important to ensure that RPC related communication with Minion at the various monitoring locations remains healthy.

If you want to verify that a specific location is operating correctly make sure that:

  1. Nodes exist and were automatically provisioned for all of the Minions at the location

  2. The Minion-Heartbeat, Minion-RPC and JMX-Minion services are online for one or more Minions at the location

  3. Response time graphs for the Minion-RPC service are populated and contain reasonable values

    • These response time graphs can be found under the response time resource on the Minion node

    • Values should typically be under 100ms but may vary based on network latency

  4. Resource graphs for the JMX-Minion service are populated and reasonable values

To interactively test RPC communication with a remote location use the opennms:poll command from the Karaf shell:

opennms:poll -l LOCATION -c org.opennms.netmgt.poller.monitors.IcmpMonitor (1)
1 Replace LOCATION in the command above with the name of the monitoring location you want to test.