Configure Horizon components to use your existing ActiveMQ instance.

Create a properties file for the ActiveMQ settings
sudo vi etc/opennms.properties.d/activemq.properties
Disable embedded ActiveMQ and set the credentials for your ActiveMQ endpoints
org.opennms.activemq.broker.disable=true(1)
org.opennms.activemq.broker.url=failover:tcp://my-activemq:61616(2)
org.opennms.activemq.broker.username=my-activemq-user(3)
org.opennms.activemq.broker.password=my-activemq-password(4)
org.opennms.activemq.client.max-connections=8(5)
org.opennms.activemq.client.concurrent-consumers=10(6)
1 Disable embedded ActiveMQ in Horizon Core instance.
2 Set the URL endpoint to your dedicated ActiveMQ instance. Replace my-active-mq:61616 accordingly. If you use ActiveMQ with SSL, replace tcp with ssl.
3 Set a user name for ActiveMQ authentication.
4 Set the password for ActiveMQ authentication.
5 By default we allow a maximum of 8 connections. Increase it depending on your size.
6 By default we allow a maximum of 10 concurrent consumers. Increase it depending on your size.
Restart Horizon Core instance to apply the changes
sudo systemctl restart opennms