We stopped seeing data on devices for specific metric families, and it appears no polls are being sent for those metrics for the devices. When we enable Detailed Poll Logging we see nothing for the problem device(s) but the Detailed SNMP Logging shows request/response pairs.
We also see one or more of the following:
All supported DX NetOps Performance Management releases
The Data Collector (DC) will not send a poll request if it is determined to be "late".
This can happen if the DC system time moves ahead by at least 90 seconds (if DC is polling items at 1 minute) or by at least 450 seconds (if DC is polling items at 5 minutes).
Ensure the Data Aggregator and Data Collector remain synchronized for time.
If this condition is seen a Data Collector restart will temporarily resolve the problem. Once a new time change is detected the problem will return.
If the problem takes place frequently, determine and resolve the environmental issue causing it to fully resolve the problem.
In releases 3.7.4+ there is a system event generated when this condition is detected. From the 3.7.4 release notes:
In 3.7.4+ releases when this condition is detected you would see Events generated on the Data Aggregator device similar to:
These are automated system events. No action is needed to raise them when the problem conditions are detected.