Are there any good example of grpc in the browser?

[Greg Keys]

I was thrilled when I started looking at gRPC as an alternative to our current implementation of websockets (crossbar.io) however that enthusiasm is dwindling the more I look into it.

Am I understanding this correctly that it's primary strength is server side service to service communication? 

My hope was to use it in the browser as well as service to service. But from what I gather the browser implementation is still using http/1.1 and it does not multiplex as a result and instead uses xhr

I have not been able to find any good (simple) examples of gRPC in the browser, I've found a couple but they are really complex to reason about, compared to the server side examples which are

typically really simple.

Are there any good examples of gRPC in the browser? are there any implementations in the browser that multiplex?

[Carl Mastrangelo]

There are examples how to run in a browser, but they typically involve a sidecar proxy.  Here is one example: https://github.com/grpc/grpc-experiments/tree/master/grpc-zpages   The full docs are here: https://github.com/grpc/grpc-web

Browsers present two challenges to gRPC.  First, they only use HTTP/2 when using TLS or SSL, which a lot of websites don't.   Second, Browsers don't expose the HTTP trailers that are needed to tell when the response is done.  To get around these issues, we have gRPC-Web protocol, which modifies the gRPC protocol slightly to be usable on HTTP/1.1.  The fetch() API for Browsers was supposed to fix the latter problem, but it has not been implemented by them, so we are kinda stuck with the work around until they do.  

Lastly, browsers use CORS when making RPCs across origin, which happens when you serve your RPCs from a different port than you HTML.  This may affect you depending on your setup.

I guess all of this is to say that getting requests (or RPCs) to work in the browser is much more complicated that it first appears, and unfortunately we can't fix it for you.  The proxy solution, while more complex, does solve a number of things you would have to otherwise do.

[Greg Keys]

By proxy do you mean something like Envoy? I'm not opposed to using something like that, it's basically serves the same purpose of the router that I'm used to using from crossbar, so I'm able to reason about that fairly easily. 

I'm also happy to hear the http/2 works with tls, everything we do is tls. so that should be fine, so long as it will multiplex over a single tcp connection. the whole reason we're looking to move away from crossbar and websockets is the scaling issue.

We are currently dependent on the crossbar router which does not cluster or scale making it a single point of failure for us, but envoy appears to have scaling working quite nicely.

I supposed what makes grpc-web so hard to reason about at the moment is the documentation, it's not very clear, the documentation lays out a simple Echo, EchoRequest, EchoResponse proto but in the actual code they implement about 20 other methods, addLeft, addRight etc..... so my mind immediately goes wtf.

I guess I'll spend a little more time sorting through the code and try to come up with something simpler to digest, grpc-web examples are definitely lacking right now.

[Spencer Fang]

Yes envoy proxy is an example of a supported proxy. gRPC on the web browser uses the grpc-web protocol, which is different from the regular grpc protocol. Here's an example of a config that makes envoy perform this translation: https://github.com/grpc/grpc-experiments/blob/master/grpc-zpages/docker/envoy/zprox.sh

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Spencer Fang

[Srini Polavarapu]

Greg, a gRPC-web tutorial is in the works here https://github.com/grpc/grpc.github.io/pull/737. If you are interested please give your feedback in the PR.