Datadog Trace Headers Not Added for Angular HttpClient Requests

[playtowork]

What's Working:
I have a web application. It has an Angular (version 14) client-side and Play framework server-side. I have followed the directions in Datadog's documentation for connecting RUM and traces. The end-to-end trace is working (with the relevant X-Datadog-* headers being sent) for the requests made via the fetch function (located in node_modules/typescript/lib/lib.dom.d.ts).

What's Not Working:

But the majority of the requests the Angular app makes to my server are via the HttpClient in node_modules/@angular/common/http/index.d.ts. None of those requests are being traced end-to-end because the relevant X-Datadog-* headers are not being injected in them. I also have some HttpInterceptors, so I thought perhaps one of them might be stripping out these headers. But the X-Datadog-* headers never seem to have been injected at all (they're never present even at the beginning of any interceptor's intercept function). This is despite the server's responses' Access-Control-Allow-Headers headers always including the headers "X-Datadog-Trace-Id", etc.

Attempted Solutions:

I'm guessing perhaps the Datadog RUM SDK's header-injection logic and Angular HttpClient's dealing with requests' headers are conflicting somehow. But I don't know how to fix it. I've tried with @datadog/browser-rum versions 5.13.0 and 5.15.0. I've also tried doing datadogRum.init() as the first thing in main.ts as well as in the ngOnInit() function of app.component.ts.

[amortemousque]

Hello @playtowork,
Thank you for your feedback. I wasn't able to reproduce the issue locally; I can see the header when using HttpClient.
Can you confirm that the allowedTracingUrls is well configured? If yes, could you provide a minimal reproducible example?

You can also contact our support to provide more details. They will be able to assist you in identifying the problem.

[danielpoonwj]

do you happen to be using pace.js in your frontend app? i encountered this issue too, turns out there's a bug that overrides XMLHttpRequest.prototype to an empty object. The Datadog browser SDK adds the headers by wrapping the prototype's methods. Removing this dependency worked for me
CodeByZach/pace#261