Built-in support of grpc-web clients

[lbensaad]

Supporting grpc-web clients is possible only through a reverse proxy like Envoy which might reduce the performance. Is it possible to add direct support as this wrapper for grpc-go?

[hsaliak]

@lbensaad is performance your only concern for this request? Have you run into any such issues?
Do you have other reasons why you would like this natively?

[lbensaad]

@hsaliak, performance is the main reason, another reason is management, a standalone gateway or proxy is an extra headache to me because i need to install it, manage it and maintain it.

[dapengzhang0]

A side note, the in progress project running gprc server as a servlet may support grpc-web client.

[simplesteph]

Performance shouldn't be of concern, but definitely ease of deployment and testing. I'd love not to have to deploy a proxy just to test a web app. Embedded in the app over the same port or another port would absolutely simplify deployment, and would probably be a one-line code as from a user perspective. Again, simplicity is the goal here

[afsluit]

We only have a small web-frontend for which we want to avoid hosting a standalone proxy. Would a small wrapper like the one linked by @lbensaad be also possible/sufficient for the java server? I'd love to take a stab at implementing the grpc-web support but am not sure if its too much for a first contribution.

[carl-mastrangelo]

@bnczk It almost certainly is too bug (but I won't stop you!) I was considering doing this as an experiment too, but wanted to go through the designs first. The big thing I see as a problem is making this secure by default. This means handling CORS and XSRF tokens, which I see as API complexity. It is not safe to not tackle those two issues, so they are part of the gRPC-Web design constraints.

[frankbenoit]

In my company, we have a Java Eclipse desktop application (Eclipse RCP) which can be remote controlled by a GRPC API.
Now we want to add a Browser-UI,
Having a proxy would increase the complexity a lot, as this is only an optional feature (but requested strongly by some users).
Please make this possible.

[ulfjack]

I posted a first draft for grpc-web support at https://github.com/EngFlow/grpc-java/tree/grpc-web. I'd welcome any feedback you have, as well as answers to my open questions (in the commit description).

[ulfjack]

@ejona86, is this something you could take a look at? It would be great if I could start submitting pieces - our internal patch set keeps growing, which makes it harder for us to stay on the latest gRPC releases. Currently looking into XSRF protection.

[visortelle]

We want to build a desktop version of our app (using Electron) that uses grpc-web

Of course, we want to get rid of the Envoy first.

The same thing for Rust works just beatifully:

https://github.com/hyperium/tonic/blob/master/tonic-web/README.md

As I can see, it's not so much code in Rust-tonic implementation.

This PR is looking in the same direction, but it's been in review for almost a year: #8596

@ulfjack how do you think, maybe your implementation may be done as a separate package? Not to wait another year.