feat(kuma-cp) KDS multiplexer

[lobkovilya]

Summary

This PR is an enhancement of existing KDS protocol, it allows Remote CP and Global CP to utilize the same grpc-stream under the hood. Thanks to that enhancement we can get rid of GlobalLbAddress and RemoteLbAddresses.

Current PR doesn't update kuma-cp.config.

Full changelog

• mux.proto for multiplexing
• ZoneResource is cluster scope (not namespace scope)

Issues resolved

Fix #XXX

Documentation

• Link to the website documentation PR

[nickolaev]

Looks great!

[nickolaev]

Good!

[nickolaev]

That looks very robust!

[jakubdyszkiewicz]

and what are the conditions of retries? Is it retried immediately? 1s? exponential retry?

[lobkovilya]

It depends on ResilientComponent that wraps KDSClient. By default backoff time is 5 sec

[lobkovilya]

Exponential is actually a good idea, probably I should implement it

[jakubdyszkiewicz]

How about this

It("should block while proper Send called", func(done Done) {
    go func() {
        request, err := serverSession.ServerStream().Recv()
        Expect(err).ToNot(HaveOccurred())
        Expect(request.VersionInfo).To(Equal("1"))
        close(done)
    }()
    err := clientSession.ServerStream().Send(&envoy_api_v2.DiscoveryResponse{VersionInfo: "2"})
    Expect(err).ToNot(HaveOccurred())
    err = clientSession.ClientStream().Send(&envoy_api_v2.DiscoveryRequest{VersionInfo: "1"})
    Expect(err).ToNot(HaveOccurred())

    resp, err := serverSession.ClientStream().Recv()
    Expect(err).ToNot(HaveOccurred())
    Expect(resp.VersionInfo).To(Equal("2"))
}, "1s")

[lobkovilya]

Thanks, much better! Didn't know about done Done

[jakubdyszkiewicz]

What is the UX if user is trying to connect to Global CP, but Zone is not present? If I was reading PR correctly, we will terminate such connection, but what is the error message in Remote? We should state that in order to connect Remote to Global, you need to add Zone resource

[lobkovilya]

@jakubdyszkiewicz you are right, now in Remote there is an error every 5 sec ZoneResource doesn't exist. The message should have some sort of instructions on how to add ZoneResource. Also discussed to create command kumactl generate zone for Remote, which will generate ZoneResource based on Ingress address.