Greyed out or "missing" data points in App Metrics for Tanzu Application Service for VMs

Products

• VMware Tanzu Application Service for VMs

Issue/Introduction

Some users may see greyed out or "missing" data points in their applications when viewing metrics details in App Metrics. This article  provides a good reference of expected behavior within App Metrics and prove as a reference that log/metric data is not missing. Rather the application or particular instances are not actively receiving trackable data points. 

Further questions should be narrowed down by referencing the aforementioned documentation and/or engaging with Tanzu support.

Environment

Product Version: Other

Resolution

Testing 

Testing below will help clarify the issue seen of missing metrics within the dashboard and references below also provide steps for users who may want to test this behavior. 

This article aims to address the confusion users experience when seeing the graphics with "missing" data points and clarify that this is expected behavior.

For more information on how to further narrow the scope of your issue, refer to Troubleshooting App Metrics. If you are still experiencing concern or questions, engage with Tanzu Support. 

To replicate the behavior and/or provide a reference to the expected results in Metrics, deploy a test application with multiple instances, in this case it is 4 AI's. 

Test

• Started a curl against the app without specifying the AI (Thu Aug 26 16:18:09 EDT 2021)
• Start curling AI 2 (Thu Aug 26 16:33:11 EDT 2021)
• Stop the first curl command to ONLY send requests to AI 2.
• Stop all curl requests (Thu Aug 26 16:42:47 EDT 2021)

For example, continuously send requests to the app without specifying a particular AI:

date ; while true ; do curl mytestapp.cfapps-06.slot-59.###.#####.com/id -H 'Cache-Control: no-cache'; sleep 5 ; done
Thu Aug 26 16:18:09 EDT 2021

Observing through Metrics shows metric data populate within our App Metrics graphic. As this is aggregated by process (Web), users see the graphic show consistent traffic until there is none destined for the app (or we stop curl requests).

The aggregated output shows that there is missing data between when the requests stop and start again.
 

When stopping curl against all AIs instead of targeting the single AI (instance 2), the graphic displays expected behavior with "missing" requests. Application traffic is reported as non-existent on any AI except AI 2.

For example, you'd use this command to stop curl against all AIs instead of targeting the single AI (instance 2):

date ; while true ; do curl mytestapp.cfapps-06.slot-59.###.#####.com -H "X-Cf-App-Instance":"8edcde2a-####-####-9f8c-c1999d13aec9:2" -H 'Cache-Control: no-cache' ; sleep 4; done
Thu Aug 26 16:33:11 EDT 2021