Incorrect data trend spike in VNA metrics after the engine is restarted

Products

• CA Virtual Network Assurance

Issue/Introduction

Upon restart of the VNA engine, there is a spike seen in the metric data that is not valid. It is not a correct representation of the current data.

 

The following report sample shows a spike at the 10/21/2019 17:20 time stamp that is not accurate.

 

Dashboard Title : Virtual Switch Pages

Report Period: 10/15/2019 00:00 EDT - 10/22/2019 23:45 EDT

View Title: Virtual Switch Packet Rate In (Trend Chart)

Subtitle: vSwitch: <name>

 

Packets In - Total Rate The total rate value of the operational metric Packets In

5-Minute Resolution, Time Zone: EDT Packets In - Total Rate (Packets Per Second)

...

10/21/2019 10:50 14.91

10/21/2019 10:55

10/21/2019 17:15 1716.49

10/21/2019 17:20 801142459.63

10/21/2019 17:25 74427.62

10/21/2019 17:30 96750.83

 

Note:

• A gap starting at 10:55 when the engine is stopped.
• The engine is restarted at 17:15
• The large inaccurate spike is seen at 17:20, the first post delta calculated metric value

Cause

Incorrect handling of post restart metric data after first delta calculation.

Environment

All VNA releases r3.7.6 and older

Resolution

The fix for this is currently scheduled for inclusion in the pending r3.7.7 release. The Fixed Issues list will include the following reference related to DE436702:

• Symptom: There is a spike while calculating Delta for VNA metrics on the reports when the engine or VNA is down for a particular time.
• Resolution: DC will now discard first poll after the VNA or Engine is down, if the value is more than 2 polls.