Working pair of controller and EUM does not work after upgrade. The controller is unable to connect to EUM and fetch EUM metrics or EUM license information.
Controller uses the property eum.cloud.host in admin.jsp to identify the end-point to eum server. In case the connection comes through a load balancer, the end point will refer to the load balancer.
However, when we upgrade the EUM server, the EUM upgrade over-writes this property value with its own default host name. Hence the controller will try to connect to the EUM directly as the eum.cloud.host value got changed.
If the direct connection is closed to the EUM, controller connection will fail and it will not be able to fetch the EUM related details.
If the EUM end point is different from the host name of the EUM server (via a proxy or load balancer), then ensure the value of the eum.cloud.host property in the admin.jsp matches the correct endpoint for connecting to EUM.