Application Insights

Check sampling rates used when collecting telemetry

union requests,dependencies,pageViews,browserTimings,exceptions,traces
| where timestamp > ago(1d)
| summarize RetainedPercentage = 100/avg(itemCount) by bin(timestamp, 1h), itemType

– via Microsoft Learn

Find out actual number of logged events, even when sampling is in place

customEvents 
| where name == '<name>'
| summarize sum(itemCount)

– via Microsoft Learn

Configure sampling settings

{
  "logging": {
    "applicationInsights": {
      "samplingSettings": {
        "isEnabled": true,
        "maxTelemetryItemsPerSecond" : 20,
        "minSamplingPercentage": 0.1,
        "maxSamplingPercentage": 100,
        "excludedTypes": "Request;Exception"
      }
    }
  }
}

– via Microsoft Learn