Latest "incremental CDS" feature breaks existing GRPC non-ADS Control Planes

[MarcinFalkowski]

Title: Latest "incremental CDS" feature (#6191 ) breaks existing Control Planes

Description:
Incremental CDS changed GRPC method from envoy.api.v2.ClusterDiscoveryService.StreamClusters to envoy.api.v2.ClusterDiscoveryService.DeltaClusters (https://github.com/envoyproxy/envoy/pull/6191/files#diff-1dbe6018649b440b0e51b4f1567d19e0R37).

From what we se, it breaks our GRPC control plane based on java-control-plane. Problem exists in non-ADS mode. Server doesn't recognise new method.

Envoy logs:

gRPC config stream closed: 12, Method not found: envoy.api.v2.ClusterDiscoveryService/DeltaClusters

Server logs:

17:31:06.370 [grpc-worker-event-loop-thread-1] DEBUG io.grpc.netty.NettyServerHandler - [id: 0x21d4c2c4, L:/127.0.0.1:50000 - R:/127.0.0.1:58883] OUTBOUND HEADERS: streamId=3 headers=GrpcHttp2OutboundHeaders[:status: 200, content-type: application/grpc, grpc-status: 12, grpc-message: Method not found: envoy.api.v2.ClusterDiscoveryService/DeltaClusters] streamDependency=0 weight=16 exclusive=false padding=0 endStream=true

config source configuration:

dynamic_resources:
  cds_config:
    api_config_source:
      api_type: GRPC
      grpc_services:
      - envoy_grpc:
          cluster_name: envoy-control-xds
        timeout: 1s

[htuch]

@fredlas can you look into this?

[kyessenov]

There is a problem in go-control-plane:

1. ADS works fine with latest envoy.
2. xDS is broken since it relies on StreamClusters
3. REST works fine since HTTP endpoints are OK