[Bug]: false positive errors in otelhttptrace for http.receive span

[mitioshi]

Component

Instrumentation: otelhttptrace

Describe the issue you're facing

We use httptrace for our http client. Very frequently we observe traces being marked as "error" due to "http: putIdleConn: too many idle connections for host" in the http.receive span.

This error is a part of an internal mechanism in net/http to pool http connections.
Transport keeps a per-host pool of idle keep-alive sockets.
In tryPutIdleConn, after a request finishes, the connection is returned to that pool. If the pool already holds MaxIdleConnsPerHost entries (default 2 if you don’t override it), the function returns errTooManyIdleHost, and the connection is immediately closed instead of being cached.

Expected behavior

This is not a client issue and not even an error(just a part of the pooling flow) and shouldn't mark traces as erroring

Steps to Reproduce

1. Start a basic Go program with an http.Client using otelhhtp

	client := http.DefaultClient
	client.Transport = otelhttp.NewTransport(
			http.DefaultTransport,
			otelhttp.WithClientTrace(func(ctx context.Context) *httptrace.ClientTrace {
				return otelhttptrace.NewClientTrace(ctx)
			}))

2. In a loop, make requests to a backend on another socket. Ensure the rate of in-flight requests is >2 (default per-host concurrency of http.Transport)
3. Observe the exported traces. Many requests should be flagged as "error"

Operating System

Debian Linux

Device Architecture

x86_64

Go Version

1.23.0

Component Version

v0.60.0

[dmathieu]

Ignoring that error in otelhttptrace makes sense to me. Do you want to open a PR?

[mitioshi]

@dmathieu Sure. I can also research if other internal http pooling errors(https://github.com/golang/go/blob/master/src/net/http/transport.go#L1013) should be ignored as well