Revert "config: unification of delta and SotW gRPC xDS (#8478)" (#8939)

This reverts commit 443bc3345b0e3db99a3df03d52f317697b99d5d7.

Signed-off-by: Matt Klein <mklein@lyft.com>

Mirrored from https://github.com/envoyproxy/envoy @ df6d3bc453167a8e9fd29662280859b4f56f0af8

envoy/api/v2/core/config_source.proto

@@ -30,12 +30,15 @@ message ApiConfigSource {
     // the v2 protos is used.
     REST = 1;
 
-    // "State of the world" gRPC v2 API, using Discovery{Request,Response} protos.
+    // gRPC v2 API.
     GRPC = 2;
 
-    // "Delta" gRPC v2 API, using DeltaDiscovery{Request,Response} protos.
-    // Rather than sending Envoy the entire state with every update, the xDS server
-    // only sends what has changed since the last update.
+    // Using the delta xDS gRPC service, i.e. DeltaDiscovery{Request,Response}
+    // rather than Discovery{Request,Response}. Rather than sending Envoy the entire state
+    // with every update, the xDS server only sends what has changed since the last update.
+    //
+    // DELTA_GRPC is not yet entirely implemented! Initially, only CDS is available.
+    // Do not use for other xDSes. TODO(fredlas) update/remove this warning when appropriate.
     DELTA_GRPC = 3;
   }
 

envoy/api/v3alpha/core/config_source.proto

@@ -30,12 +30,15 @@ message ApiConfigSource {
     // the v2 protos is used.
     REST = 1;
 
-    // "State of the world" gRPC v2 API, using Discovery{Request,Response} protos.
+    // gRPC v2 API.
     GRPC = 2;
 
-    // "Delta" gRPC v2 API, using DeltaDiscovery{Request,Response} protos.
-    // Rather than sending Envoy the entire state with every update, the xDS server
-    // only sends what has changed since the last update.
+    // Using the delta xDS gRPC service, i.e. DeltaDiscovery{Request,Response}
+    // rather than Discovery{Request,Response}. Rather than sending Envoy the entire state
+    // with every update, the xDS server only sends what has changed since the last update.
+    //
+    // DELTA_GRPC is not yet entirely implemented! Initially, only CDS is available.
+    // Do not use for other xDSes. TODO(fredlas) update/remove this warning when appropriate.
     DELTA_GRPC = 3;
   }