Enable ApplicationInsights based on Configuration

Question

I want Azure ApplicationInsights to only be used in an ASP.NET Core application if specified by a Configuration value that is set in appsettings.json.

I put this in my _Layout.cshml to disable client-side insights:

    @if (Configuration.GetSection("UseInsights").Get<bool>())
    {
        @Html.Raw(JavaScriptSnippet.FullScript)
    }

But server-side telemetry is still sent, so I added this when its disabled via Configuration:

TelemetryConfiguration.Active.DisableTelemetry = true;

This stopped Request and Exception data from being sent, but things like CPU usage were still being sent and visible on my Insights dashboard.

What I think would be the proper method is to enable the .UseApplicationInsights() extension on WebHost.CreateDefaultBuilder() conditionally, but this is a chicken and egg scenario since I don't have access to the Configuration settings until after the Host has been built. Is there somewhere I can fully disable insights after calling BuildWebHost()?

Valuator Valuator · Accepted Answer · 2018-03-23T20:46:49

Here is what I did to completely get rid of any Azure Application Insights when disabled.

I created an Interface for the JavaScript snippet that gets injected for client-side telemetry:

public interface IInsightsJavaScriptSnippet
{
    string FullScript { get; }
}

With two implementations, one that wraps Microsoft.ApplicationInsights.AspNetCore.JavaScriptSnippet for when Insights are enabled:

public class InsightsJavaScriptSnippet : IInsightsJavaScriptSnippet
{
    private readonly JavaScriptSnippet _snippet;

    public InsightsJavaScriptSnippet(JavaScriptSnippet snippet)
    {
        _snippet = snippet;
    }

    public string FullScript => _snippet.FullScript;
}

And another that outputs an empty string for when they are not:

public class BlankJavaScriptSnippet : IInsightsJavaScriptSnippet
{
    public string FullScript => string.Empty;
}

I then register one or the other depending on the Configuration value. services.AddApplicationInsightsTelemetry() will register JavaScriptSnippet which will then be injected into the constructor for my InsightsJavaScriptSnippet:

if (Configuration.GetSection("UseInsights").Get<bool>())
        {
            services.AddApplicationInsightsTelemetry(Configuration["ApplicationInsights:InstrumentationKey"]);
            services.AddSingleton<IInsightsJavaScriptSnippet, InsightsJavaScriptSnippet>();
        }
        else
        {
            services.AddSingleton<IInsightsJavaScriptSnippet, BlankJavaScriptSnippet>();
        }

Then, I inject IInsightsJavaScriptSnippet into _Layout.cshtml instead of the Microsoft JavaScriptSnippet:

@inject MyApp.Services.IInsightsJavaScriptSnippet JavaScriptSnippet
// ... snipped code
<head>
    @Html.Raw(JavaScriptSnippet.FullScript)
</head>

Which adds nothing to the HTML if we aren't using Insights.

Enable ApplicationInsights based on Configuration

2 Answers