Setting cloud role name for Application Insights customEvent (health check, snapshot collector) and customMetric telemetry events

Matt Buckleman 0 Reputation points


  • Azure App Service on Windows, running .net core 3.1 apps (web and API)
  • Running on 4 separate app service plans in 4 regions behind Azure FD
  • Logging app insights through the package in our actual code (not just turning it on in the app service itself)


  • We have our own ITelemetryInitializer in our code and are setting the role name via telemetry.Context.Cloud.RoleName
  • Most app insights events respect and use the role name we set, including any custom events we send


  • However, there are things that the app service itself seems to send that do not. Specifically, the app insights data for customMetrics (e.g. "System.Runtime|CPU Usage" and other performance metrics) and customEvents (e.g. "AppInsightsSnapshotCollectorLogs") that are Not sent by our own code do not use the role name we have set
  • This makes sense as they would not go through our telemetry initializer, but we still need to be able to set the role name somehow
  • I need to be able to do this via env vars so I can set them on a per-slot basis. This has already been a real headache because our staging slots were pinging our production app insights instance with lots of data.
  • There is no documentation on how to disable, for example, snapshot debugger on a per-slot basis

Attempted solutions:

I have tried setting environment vars in the azure portal using these vars:

  • ApplicationInsights_CloudRoleName

I am assuming it is the app service framework that is logging these, and it is therefore using WEBSITE_HOSTNAME - but that cannot be set via the azure portal.

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  1. Ryan Hill 26,241 Reputation points Microsoft Employee

    Hi @Matt Buckleman

    I think you should be able to disable the snapshot debugger via slot through configuration settings. Easiest way is add:

      "ApplicationInsights": {
        "SnapshotCollector": {
          "IsEnabled": false

    to an appsettings.<slot>.json file or pin ApplicationInsights:SnapshotCollector:IsEnabled app setting to the preferred slot. customMetrics and customEvent is not part of the ITelemetryInitializer pipeline. To still use a cloud role name, you need to go the SDK route and disable auto instrumentation. Use TelemetryClient.Track() to send the custom metric:

    var telemetry = new MetricTelemetry("MyCustomMetric", 42);
    telemetry.Context.Cloud.RoleName = "MyCustomRoleName";
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