Headers mangled without previous async middleware

[orthoplex64]

When using app.UseHeaderPropagation(); as the first middleware in the pipeline and sending many simultaneous requests, I've observed incorrect headers being propagated sometimes.
When inserting any async middleware before header propagation (e.g. app.Use(async (context, next) => await next.Invoke());), all propagated headers are correct.

[alefranz]

Hi Christopher,
thanks for reaching out.
Which version of AspNetCore are you using?
Do you have a repro to share?
Thanks

[orthoplex64]

I'm using ASP.NET Core 2.2. Sorry, I don't have a repository, but I'll put one together and get back to you.

[alefranz]

That would really help.

The middleware get the headers from the HttpContext and put then in a AsyncLocal so I can't think of a reason when this could fail.

Are you consuming an HttpClient configured with the header propagation also from outside of the request pipeline (e.g. from a IHostedService)?

[orthoplex64]

Here's a repository with a demo project: https://github.com/orthoplex64/dotnet-demos
The HttpClient is being consumed within the request pipeline, in a controller action

[orthoplex64]

I submitted this issue to the ASP.NET Core project as well, and it was identified with a known problem with Kestrel: dotnet/aspnetcore#15384

[alefranz]

Thanks! this really helps to understand the problem!
I'll work on a solution

[alefranz]

I've released 3.0.2 which address the issue.
Thank you for your help!