Issue
While creating an EUM app in an on-premise Controller, it fails with the error "internal server error. See server.log"
The Controller UI gives the same error when tried with "Create an Application manually" or "Create an Application using the Getting Started Wizard." This error is even seen when both EUM and Events Service are up.
Diagnosis
When checking the Controller's server.log for the same timeframe, it seems like EUM Processor is not reachable from the browser where the Controller UI is accessed to create this EUM app:
Communication failure with service (http://<EUM-HOST>:7001/v2/application/EUM-AAB-AUB/resource-timing): Unexpected HTTP error 500: {"code":500,"message":"There was an error processing your request. It has been logged (ID ecac6f5d92fddeb5)."}|#]
To further validate this, gather the output (o/p) of the following URL from the same browser where this error is seen inside the Controller UI:
http://<EUM-HOST>7001/eumcollector/get-version
This would fail as from the same browser the EUM is not reachable.
Solution
While creating an EUM app from the Controller UI, the browser validates the communication to the EUM Processor. To resolve this issue, grant access to the EUM Processor (TCP/7001) from the web browser.
Once this is done, you should be able to create an EUM app successfully.
Note: 7001 is default HTTP port for eum processor.
