Here is how we can troubleshoot & try resolve some common issues:
1) Check points :
If the load has been spotty?
What Controller EUM server setup : SAAS or On-Prem ? Check for any connectivity issues to the server.
Does their web applications have the JS Agent present or not.
How is the adrum.js injection done?
Check if page and AJAX limit is hit. Because its possible this could have caused as most of the load going to pages that were not captured due to being past the limits. If so get that fixed first.
Check if there are any changes in the beacon detail : EUM Global account name or EUM App-Key was changed or somehow some pages are using an incorrect key or so?
Check both Controller logs and EUM processor logs (this applies more to an on prem EUM Server ) to see if you can spot any errors or anything not giving you an idea on the blip.
Check controller logs to see if there was a connectivity issue between the Controller and EUM server?
Check EUM processor logs to see if EUM server was processing data regularly. Specifically in the time range of the reported gap. Or if there really was a gap.
You can also check the dropped beacons log to see if any beacons were dropped around that time and if so what was the reason.
Licensing Issue: Another rarecase but possible cause could be a downgrade in license type from EUM PRO to EUM LITE . Then you should see below error in EUM server logs:
15:34:49.844 +0700 Downgrade trial accounts-1 AD.LicenseLifecycleManage INFO Downgrading EUM trial features as necessary
Solution: This would need Order OPS/sales intervention on getting the EUM pro license again.
A mismatch in keys disabling EUM automatically:
15:34:51.405 +0700 dw-181 - GET /v2/account/PTTelekomunikasiIndonesia-a0Q8000000BWzGLEA1/application/EUM-AAB-AUB/metrics?timestamp=1483000380000 dropwizard.LoggingExcepti ERROR | Error handling a request: 7bae2de7bc684334 | com.appdynamics.eum.rest.exception.ApiException: Not an active app: applicationKey=EUM-AAB-AUB at com.appdynamics.eum.api.resources.DownloadDataResource.validateApplication(DownloadDataResource.java:380) | at com.appdynamics.eum.api.resources.DownloadDataResource.sendMetrics(DownloadDataResource.java:125)
Solution: Disable and re-enable EUM for each application. However, this may cause the APP KEY to change for the applications. If it does update, we need to modify the adrum.js file for each application to ensure they are using the correct APP KEY.