Unable to scrape HTTP/2-only endpoint

[Daniel15]

What did you do?
Added an endpoint to my Prometheus config that only responds via HTTP/2. It's a gRPC service that I've also added a /metrics HTTP endpoint to, and gRPC services only speak HTTP/2 by default.

What did you expect to see?
Data is properly scraped.

What did you see instead? Under which circumstances?
Prometheus UI says:

Get https://xxxxxxx/metrics: EOF

Server says:

fail: Microsoft.AspNetCore.Server.Kestrel[0]
HTTP/2 over TLS was not negotiated on an HTTP/2-only endpoint.

Environment

• System information:

Debian "testing"
Linux 5.5.0-2-cloud-amd64 x86_64

• Prometheus version:

prometheus, version 2.15.2+ds (branch: debian/sid, revision: 2.15.2+ds-2)
  build user:       pkg-go-maintainers@lists.alioth.debian.org
  build date:       20200113-10:10:54
  go version:       go1.13.6

[roidelapluie]

See prometheus/common#233

[Mario-Hofstaetter]

Has this been resolved yet?
I am getting the very same error using Prometheus 2.23.0 and ASP.NET Core Kestrel GRPC Service.

Prometheus UI: Get "https://host.docker.internal:5011/metrics?format=prometheus": EOF
Kestrel: [2020-12-03 23:04:58Z ERR] Microsoft.AspNetCore.Server.Kestrel HTTP/2 over TLS was not negotiated on an HTTP/2-only endpoint.

ARGH, I guess it's because of this: prometheus/common#261

[roidelapluie]

More like #7588 and #8143

[Daniel15]

@Mario-Hofstaetter I don't think it's fully fixed yet. For now you'll have to enable HTTP/1.x in your ASP.NET service too, for example by adding this in appsettings.json:

  "Kestrel": {
    "EndpointDefaults": {
      // Temporarily enabling HTTP/1 due to https://github.com/prometheus/prometheus/issues/7237
      "Protocols": "Http1AndHttp2"
    }
  }

This is what I did in my service (https://github.com/Daniel15/dnstools/blob/master/src/DnsTools.Worker/appsettings.json#L9-L14) to allow Prometheus to connect.

[roidelapluie]

We are looking to see if the Golang HTTP/2 issues are fixed or not, any help is welcome.

[valdemarpavesi]

We are looking to see if the Golang HTTP/2 issues are fixed or not, any help is welcome.

there is an update here:
#5938