Having issues with H2C

Questions / Help
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1

I have this app that listens to both regular HTTP and gRPC requests. To do this, I listen to HTTP2 only (with prior knowledge) and configured fly.toml to use h2_backend = true.

[http_service]
  internal_port = 8080
  force_https = true
  auto_stop_machines = 'stop'
  auto_start_machines = true
  min_machines_running = 0
  processes = ['app']

  [http_service.http_options]
    h2_backend = true

This wasn’t ideal, but it worked as long as connections started with http2 prior-knowledge. Until it didn’t… not sure when, but this recipe stopped working without any code/config changes.

The errors seem to be from the edge proxy, not hitting the app

[PU02] could not complete HTTP request to instance: hyper error: http2 error (source: stream error received: unspecific protocol error detected)

Does anyone have any hints on this? Or a similar situation? From the docs, this seems to be the proper way… terminating TLS on the edge and forward H2C…

2

Damn… I’m answering myself… after browsing multiple issues, looking for similar problems, I bumped into this: https://community.fly.io/t/grpc-http2-does-not-work-on-separate-port/14714

Turns out this is a .NET issue… probably upgrading to .NET 10 caused this… can’t say for sure… anyway… this is sorted.

3

Just a quick note that there is still an issue on Fly’s side. H2C traffic should use http scheme, not https. Hopefully someone from Fly will read this.

5

Hey @goncalo-oliveira

Thanks for the report! I must have broken this when I made our proxy keep the original :authority while forwarding requests.

I’ll post an update here once it’s fixed.

6

@goncalo-oliveira This should be fixed now.

7

Thanks @pavel, I appreciate it. Will revert code changes and re-test.