Logical Router Interface Metrics are Missing or Displaying "No Data to Display"

Products

• VMware Aria Operations (formerly vRealize Operations) 8.x

Issue/Introduction

• Router Interface Statistics and Statistics metric folders for a Logical Router intermittently disappear and reappear in Aria Operations.

• Navigating to Logical Router > Metrics and selecting any of the metrics, the UI displays "No data to display".
  
• Following error is observed on /storage/log/vcops/log/adapters/NSXTAdapter/NSXTAdapter_###.log:
  
  

  WARN  [NSX-T Metric Collector thread 17, time: YYYY-MM-DDTHH:MM] (112) com.vmware.adapter3.nsxt.collector.managercollector.metrics.LogicalRouterMetricCollector.fetchRouterStatistics - Logical Router Stats in current cycle is lower than previous stats. Resulting in negative values - hence skipping the publishing of those metrics for current cycle for logical router : ####-####-#####-####

Environment

Aria Operations 8.18.x
NSX 4.2.x

Cause

This behavior is by product design.

For Logical Router statistics, Aria Operations calculates metrics based on the difference between the current and previous statistics collected from NSX. When the current value is lower than the previous value, the calculated difference becomes negative.

To prevent inaccurate rate and usage calculations, the adapter intentionally skips publishing these metrics whenever negative values are detected.

Resolution

Below workaround can be implemented only if negative statistics are considered acceptable in the environment.

1. SSH to the Aria Operations primary node.
2. Take a backup of file  "/usr/lib/vmware-vcops/user/plugins/inbound/NSXTAdapter3/conf/NSXT.properties" 
   

   cp  /usr/lib/vmware-vcops/user/plugins/inbound/NSXTAdapter3/conf/NSXT.properties  /usr/lib/vmware-vcops/user/plugins/inbound/NSXTAdapter3/conf/NSXT.properties.bkp 

3. Edit "/usr/lib/vmware-vcops/user/plugins/inbound/NSXTAdapter3/conf/NSXT.properties" file using vi editor.
4. Add property "SKIP_NEGATIVE_STATS_FOR_ROUTER" and set it to value "false".

Additional Information

To validate the issue, confirm what stats has been received from NSX API, enable debug logging "com.vmware.adapter3.nsxt.collector.managercollector.metrics.LogicalRouterMetricCollector" for collector logs.

Search for following keywords in NSX adapter logs.

logger.info("Prev stats for router: "logicalRouter.getid()" is: "+ prevRouterStatistics);
logger.info("Current stats for router: "logicalRouter.getid()" is: "+ routerStatistics);