Traces send by http protocol fail in new Otel collector receiver

What version of OpenTelemetry are you using?

0.23.0

What version of Node are you using?

v14.15.2

Please provide the code you used to setup the OpenTelemetry SDK

All code is here https://github.com/open-telemetry/opentelemetry-js/tree/main/examples/tracer-web

What did you do?

I used this project example and new Otel collector (0.29.0).

What did you expect to see?

Traces OK in collector

What did you see instead?

All traces send to the Otel Collector failed (404).

Additional context

No additional.

What I think about this issue

Traces are send with beacon with a body string, so the content-type is text/plain. New collector (0.29.0) is less permissive and expect an application/json

[jufab]

I think application/x-protobuf is for GRPC protocol. application/json is for HTTP protocol

or “Content-Type: application/json” request header when sending JSON encoded Protobuf payload

[niko-achilles]

@mogest if you use opentelemetry-collector of version 0.29.0 then, an elegant workaround to fallback to xhr without mutating the navigator.sendBeacon property is to define the config of Collector Trace exporter as follows:

new CollectorTraceExporter({
        headers: {},
      })

or if you want to be explicit, update npm packages to version 0.24.0 :

new CollectorTraceExporter({
        headers: {
              "Content-Type": "application/json"
             },
      })

note opentelemetry-collector of version 0.29.0 is released and that workaround may not be needed.