Eliminate custom header x-grpc-web

As far as I can tell, there is no actual functional purpose for the header x-grpc-web, aside from a vanity bump that it is possible to detect use of Improbable’s gRPC web client.

Why is the header added? Of course there are significant problems with this approach. If gRPC web is being used cross-domain, the x-grpc-web header must be included in the Access-Control-Allow-Headers response. And, naturally, the custom header triggers a CORS pre-flight which costs an entire HTTP round-trip, and is a head-of-line blocker for initial calls to the server.

So, here is my question:

1. Why was this header added in the first place?
2. Perhaps related to point 1, does this header actually trigger any functionality? Is it triggered when using Improbable’s server side tools, or all gRPC servers?
3. Why can’t it be disabled, since the library works fine if the header is eliminated?

[jonnyreeves]

Works for me (although it would be 0.9.0)

On Wed, 6 Feb 2019, 17:39 Johan Brandhorst <[e-mail] wrote:

Thanks for confirming Marcus, I’m tempted to say we shouldn’t bother and just remove it with a major version bump (0.8.0). Any objections?

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[jonny-improbable]

Closing this issue in favor of #346; to summarise, our plan is to remove the x-grpc-web header from the client.