CPU usage slowly increases over time #690

I had previously used Application Insights, but no longer do, however the App Insights code remained in my app. I noticed when I recently migrated hosts and upgraded to .NET Core 2.1.0-rc1 that the CPU usage gradually increased over the course of a few days.

The drops back to 0 are Docker container restarts.

Removing Application Insights from the site results in a steady almost-zero CPU usage.

See also this Twitter thread, though there's not much more there.

Repro Steps

1. Add Application Insights (2.3.0-beta2) to an ASP.NET Core MVC app via NuGet and Startup.cs
   app.AddApplicationInsightsTelemetry("{no-longer-valid instrumentation key}")
2. Setup some sort of synthetic monitoring to hit the site every minute
3. Wait a couple days ¯_(ツ)_/¯

Actual Behavior

• CPU slowly creeps up over the course of a few days

Expected Behavior

• CPU remains stable

Version Info

SDK Version : 2.1.0-rc1
.NET Version : 2.1.0-rc1
How Application was onboarded with SDK(VisualStudio/StatusMonitor/Azure Extension) :
OS : Ubuntu 16.04
Hosting Info (IIS/Azure WebApps/ etc) : Azure VM