Could not load type 'Microsoft.ApplicationInsights.Extensibility.ITelemetryInitializer' with version 3.0.0

[yohny]

Hello,
I have just updated the package Microsoft.ApplicationInsights.WorkerService from version 2.23.0 to 3.0.0 in Azure functions project running on .NET 10 (isolated worker model) and when launched, it produces the following error:

Unhandled exception. System.TypeLoadException: Could not load type 'Microsoft.ApplicationInsights.Extensibility.ITelemetryInitializer' from assembly 'Microsoft.ApplicationInsights, Version=3.0.0.1, Culture=neutral, PublicKeyToken=31bf3856ad364e35'

Are Azure function running .NET 10 not supprted by this new release?

[xinfli]

We met same issue.

It's nothing related to dotnet core 10, our Azure function is running with dotnet core 8.

The root cause is Microsoft.ApplicationInsights.WorkerService 3.0.0 depends on Microsoft.ApplicationInsights 3.0.0, but the interface Microsoft.ApplicationInsights.Extensibility.ITelemetryInitializer does not exist in assembly Microsoft.ApplicationInsights 3.0.0 any more.

We fixed it by revert to 2.23.0.

[harsimar]

Hi,
Thanks for reporting this. I know it's frustrating to run into a breaking change like this - @xinfli is correct that ITelemetryInitializer has been removed (in favor of OpenTelemetry processors & resource detectors). Taking a look at existing documentation within this repo for breaking changes, concepts, and the worker service specifically, we can do a better job of documenting the alternatives to ITelemetryInitializer. I will look into fixing these documentation gaps and am open to feedback on what kinds of examples would be more beneficial to document.

That being said, I'd like to take a look at a minimal repro so that we can provide more targetted assistance. I am curious about if/how ITelemetryInitializer is currently being used in the application - are you trying to implement your own initializer or trying to configure one that previously existed in 2.x? Are there any other packages in use that have transitive dependencies on 2.x Application Insights packages?

[snelljef]

Also had this issue. For me personally anyway, my function app includes Microsoft.ApplicationInsights.WorkerService 3.0.0 and Microsoft.Azure.Functions.Worker.ApplicationInsights 2.50.0.

In my Program.cs, I just register them with:

var builder = FunctionsApplication.CreateBuilder(args);
builder.ConfigureFunctionsWebApplication();
builder.Configuration.AddJsonFile("host.json", true, true); // Attempting to control log levels
builder.Services
    .AddApplicationInsightsTelemetryWorkerService()
    .ConfigureFunctionsApplicationInsights();

and nothing really else from there. Reverting to Microsoft.ApplicationInsights.WorkerService to 2.23.0 is my solution for now too.

[nickyg91]

@harsimar, a minimal repro is very easy to do. Create a new Azure Function via File > New > Project/Solution.
In my case I created a service bus listener using .NET 10. Once the project scaffolds, upgrade all the nuget packages and the issue should occur when you attempt to run the application. It should exit with the error mentioned above.

[yohny]

In my case I only have minimalistic setup described here https://learn.microsoft.com/en-us/azure/azure-functions/dotnet-isolated-process-guide?tabs=ihostapplicationbuilder%2Ccode%2Cwindows#configure-startup, which means I only installed packages Microsoft.ApplicationInsights.WorkerService and Microsoft.Azure.Functions.Worker.ApplicationInsights and have simple initialization code in Program.cs:

builder.Services
    .AddApplicationInsightsTelemetryWorkerService()
    .ConfigureFunctionsApplicationInsights();

[harsimar]

Thanks all for the responses - I'll look deeper into the integration with Microsoft.Azure.Functions.Worker.ApplicationInsights. It seems that the 2.50.0 version of Microsoft.Azure.Functions.Worker.ApplicationInsights takes dependencies on 2.x ApplicationInsights packages, and when used along the 3.x version of Microsoft.ApplicationInsights.WorkerService this causes issues. We will collaborate with the functions team so that their next version is compatible with 3.x.