What happens when a counter rolls over in CAPM?

Products

• CA Performance Management
• Network Observability

Issue/Introduction

What happens when a counter rolls over between polls?

When a 32 bit counter is associated with a 64 bit metric, it is common for the values to exceed the limit of the 32 bit counter and 'rollover'

When this happens, the value we get makes for an impossible delta. But even a 64 bit counter can rollover if the metric is busy.

This article describes what happens when a counter rolls over.

Environment

Dx NetOps Performance Management all versions

Resolution

On the DCs, there is a file that tracks rollovers:

/opt/IMDataCollector/apache-karaf-2.4.3/data/log/CounterRollover.log

 
In this file, you'll find messages like:

2016-12-22 16:55:11,061 | INFO | xtenderThread-65 | CounterRollover | core.rdp.AbstractDeltaController 291 | 186 - com.ca.im.data-collection-manager.core.interfaces - 2.8.0.SNAPSHOT | | Setting (64 bit) largeDeltaValueThreshold to 9223372036854775807

The above tells you the threshold for 64 bit counters.  For 32 bit counters, the limit is 2147483648:

The following is an example of a delta being > 2147483648, so we drop it.

We also indicate when rollover happens, but in this case we don't drop, we calculate the delta and use it.

Additional Information

TechDocs : DX NetOps 23.3  - Configure Counter Behavior

Increase logging:

By default, we only keep 2 files, 100MB each. If you wish to keep more, you can edit the following file on the DC: 

org.ops4j.pax.logging.cfg

Look for;

log4j.appender.CounterRollover.maxBackupIndex=

Increase the number to 4 or 5. This will save 5 or 6 files.