Change volume of performance counters in Application Insights PaaS

Question

Default Sitecore logs performance counters every 5 second from each of the 4 roles. This is a bit much for our needs. Is it possible to reduce the sampling intervall of performance counters without reducing the other logging?

I see that in application.config file in the root directory this is set like this:

<Add Type="Microsoft.ApplicationInsights.WindowsServer.TelemetryChannel.AdaptiveSamplingTelemetryProcessor, Microsoft.AI.ServerTelemetryChannel">
  <MaxTelemetryItemsPerSecond>5</MaxTelemetryItemsPerSecond>
</Add>

But I want to change it to sample every 5 minutes instead of 5 seconds, not limit the number of samples per second. Is this possible?

Answer 1

In short

The setting MaxTelemetryItemsPerSecond is not setting the sampling interval to 5 seconds, but it is telling how many items to check in 1 second, so you cannot set it to 5 minutes.

In more details

Sampling is a feature in Azure Application Insights. It is the recommended way to reduce telemetry traffic and storage, while preserving a statistically correct analysis of application data.

There are three alternative sampling methods:

• Adaptive sampling
• Fixed-rate sampling
• Ingestion sampling

In this case you are using Adaptive sampling which is the default sampling method and automatically adjusts the volume of telemetry sent from the SDK. It doesn't operate at low volumes of telemetry, so an app in debugging or a website with low usage won't be affected.

Couple of things you can do to lower the samplings:

1. Use ExcludedTypes or IncludedTypes as additional parameters, for example:

   <ExcludedTypes>Trace;Exception</ExcludedTypes>
   <IncludedTypes>Request;Dependency</IncludedTypes>
   

2. Disable the AdaptiveSamplingTelemetryProcessor and configuring fixed-rate sampling, for example:

     <Add  Type="Microsoft.ApplicationInsights.WindowsServer.TelemetryChannel.SamplingTelemetryProcessor, Microsoft.AI.ServerTelemetryChannel">
          <!-- Set a percentage close to 100/N where N is an integer. -->
          <!-- E.g. 50 (=100/2), 33.33 (=100/3), 25 (=100/4), 20, 1 (=100/100), 0.1 (=100/1000) -->
           <SamplingPercentage>10</SamplingPercentage>
      </Add>
   

Learn more here: https://docs.microsoft.com/en-gb/azure/azure-monitor/app/sampling