Preflight OPTION request fails on h2 protocol with grpc-web

[nadilas]

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Issue Type:

• [x ] Bug report
• Feature request

What happened:
GRPC calls made from the browser are preceeded with a preflight request. These requests are made via http/1.1 which causes the h2 protocol to fail.

What you expected to happen:
Preflight check to be accepted by the h2 protocol and the request being normally routed.

How to reproduce it (as minimally and precisely as possible):
Make calls from a web browser using https://github.com/improbable-eng/grpc-web

Anything else we need to know?:

Environment:

• linkerd/namerd version, config files: v1.5.0
• Platform, version, and config files (Kubernetes, DC/OS, etc): windows server 2012
• Cloud provider or hardware configuration:

[adleong]

Hi @nadilas! I believe this is effectively a duplicate of #766. Do you agree?

[nadilas]

Hi @adleong, technically yes. If you can upgrade http/1.1 to http/2.0 that would take care of the preflight requests as well. However the difference is in the use case, all my requests are http/2.0 only the ones generated by the browser which I can’t control are http/1.1.
To be honest it’s completely blocking my project, because no grpc calls are working from the browser.

[adleong]

That is unfortunate. I'm not familiar with the architecture of grpc-web, is it at all possible to disable the http/1.1 preflight requests?

Unfortunately, until Linkerd supports protocol detection or upgrading, I don't think there's anything we can do.

[nadilas]

I would if I could :) those preflight requests are generated by the browser (e.g. Chrome) not grpc-web. I have no control over that.

[nadilas]

@adleong When do you expect this feature to land?

[adleong]

@nadilas I'm not aware of anyone actively working on it, so probably not in the near term.

[nadilas]

@adleong thanks for the info. That means I have to take Linkerd out of my stack for now. Where can I track when this feature will be implemented?

[wmorgan]

@nadilas are you on Kubernetes? we have protocol upgrade in Linkerd 2.x, but that's K8s-specific right now. Alternatively, #766 is the issue to track.

[nadilas]

@wmorgan great, thanks! I’m not on Kubernetes. So I’ll just have to wait. 🙂