support gRPC streams in addition to HTTP

[markfisher]

/area API
/kind dev

If Elafros defines a gRPC service that passes messages via bidirectional streams, any binding for that gRPC service could be used several ways:

1. directly within applications that add a binding as a dependency
2. indirectly via a bridge (e.g. HTTP -> gRPC) provided as a sidecar/ambassador container
3. in function invokers, so that user code is simply called with an idiomatic stream type for its language

For example:

syntax = "proto3";

package function;

message Message {
	bytes payload = 1;
	map<string, string> headers = N;
}

service MessageFunction {
  rpc Call(stream Message) returns (stream Message) {}
}

Since gRPC traffic can be handled by Istio/Envoy, the management of traffic, policies, etc. should be consistent.

The goal of this issue is to establish the need for the foundational primitive that enables building higher level streaming constructs. From a platform implementer’s perspective, the domain of stream processing can lead to many challenges. It may not necessarily be within the realm of Elafros to address those challenges directly, but Elafros should provide the building blocks that enable streaming systems to be built in a way that aligns with the paradigm shift in developer experience being driven by serverless functions.

[bsnchan]

/assign @bsnchan @dprotaso

[bsnchan]

It looks like the PR to update to the latest Istio version (#1228) does not support gRPC out of the box.

All the requests are sent using HTTP1 instead of the expected h2c.

[bsnchan]

It looks like in order to support GRPC, we'll need the following:

• The knative-ingressgateway will need to have an exposed port with HTTP2 or GRPC as the protocol. (spec here)
• The revision service's ports must also be named with the protocol (spec here)

[evankanderson]

FWIW, golang/go#25363 has been closed, which means that h2c support has landed in golang.org/x/net/http2/h2c.

[dprotaso]

Awesome thanks for the update - I’ll take a look at this issue again this week

…

On Mon, Jul 30, 2018 at 18:40 Evan Anderson ***@***.***> wrote: FWIW, golang/go#25363 <golang/go#25363> has been closed, which means that h2c support has landed in golang.org/x/net/http2/h2c. — You are receiving this because you were assigned. Reply to this email directly, view it on GitHub <#813 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AABIghSsixCm7hofavWRZWnsZ5SlqSRIks5uL4tLgaJpZM4TzQxM> .

[mattmoor]

/area networking

Is this a duplicate of: #707 If not, how is it different?

/remove-area API

I'm removing the API area for now because the control-plane implications are not clear. If we need control plane changes, then please detail them and add back the label (maybe in a dedicated issue, since this feels like a meta-tracking-issue for an epic).