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

Question

Situation:

• 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)

Background

• 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

Problem

• 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
• WEBSITE_CLOUD_ROLENAME
• APPLICATIONINSIGHTS_ROLE_NAME

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.

Answer 1

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";
TelemetryClient.Track(telemetry);