HTTP instrumentation modifies headers casing of outgoing requests

[marcinjahn]

What happened?

It's about the package @opentelemetry/instrumentation-http.

The http auto-instrumentation should not modify the request in any other way than context injection. Currently, the library does modify the casing of request headers. Even though in theory that should not matter, there are servers that require incoming headers to have some predefined casing, e.g. all letters uppercase.

This behavior potentially (and in practice too, as I was able to experience that :)) breaks applications that would work completely fine before installing http instrumentation.

Steps to Reproduce

Try to send an HTTP request with header: { MY_HEADER: 123 }

Expected Result

The target server should receive a request with header { MY_HEADER: 123 }.

Actual Result

The target server receives a request with header { my_header: 123 }.

OpenTelemetry Setup Code

No response

package.json

No response

Relevant log output

No response