Adding newly created header by Asp.Net HeaderPropogation library to telemetry - .net-core

Question

services.AddHeaderPropogation(o =>
{
o.Headers.Add("Id")
o.Headers.Add("Id", context => {
return new StringValues(Guid.NewGuid().ToString())
});
});
The above code helps me to create a header called id if it doesnt exist with a new guid and if it exists, it would just use the value. This is using Microsoft Header Propogation nuget package. And it works.
But now i have a requirement to add this to Azure Application insights, but the standard way of doiing it only works when the incoming request has headers. If the new GUID is created, it doesnt trigger the ITelemetryInitializer call.
Because for adding Telmetry custom values, we have a class which inherits ITelemtryInitializer and inside that i do call to Request.Headers like below:
var requestTelemetry = telemetry as RequestTelemetry
if(context.Request.Headers.TryGetValue(id, out var value))
requestTelemtry.Properties[id] = value.ToString()
But the above line is never triggered since the Request.Headers never had this id. This id will be created only by the middleware when the api calls the next service.
So my question, is there a way to call the telemetry classes from the Startup> ConfigfureServices and inside the HeaderPropogation code, so that as soon as the new GUID is created, i can add it to telemtry. All the examples of adding to telemetry shows either from controller or DI. How to call it from the Startup itself ?
Or is there a better way to achieve the same ?

Answer 1

Let me post the solution I found. I didnt need to have a telemetryinitializer class to populate the guid in another class. I wanted it to be added as soon as we create it, so this is how i modified th header propogiation code in services in startup.
services.AddHeaderPropagation(options =>
{
var correlationId = "YourId";
options.Headers.Add(correlationId, context => {
var requestTelemetry = context.HttpContext.Features.Get<RequestTelemetry>();
if (context.HttpContext.Request.Headers.TryGetValue(correlationId, out var value))
{
requestTelemetry.Properties[correlationId] = value.ToString();
return value.ToString();
}
else
{
var guidId = Guid.NewGuid().ToString();
requestTelemetry.Properties[correlationId] = guidId;
return new StringValues(guidId);
}
});
});
Key for me has been the realization i can get RequestTelemetry anywhere we want in the code with this properties option.
var requestTelemetry = context.HttpContext.Features.Get<RequestTelemetry>();