Add bi-di streaming variants of the discovery APIs. (#79)

Versioning for gRPC streaming APIs.

api/cds.proto

@@ -13,7 +13,7 @@ import "google/protobuf/wrappers.proto";
 
 service ClusterDiscoveryService {
   // Return list of all clusters, this proxy will load balance to.
-  rpc StreamClusters(ClusterDiscoveryRequest)
+  rpc StreamClusters(stream ClusterDiscoveryRequest)
       returns (stream ClusterDiscoveryResponse) {
   }
 
@@ -27,11 +27,16 @@ service ClusterDiscoveryService {
 }
 
 message ClusterDiscoveryRequest {
-  Node node = 1;
+  // The version_info provided in the request messages will be the version_info
+  // received with the most recent successfully processed response or empty on
+  // the first request.
+  bytes version_info = 1;
+  Node node = 2;
 }
 
 message ClusterDiscoveryResponse {
-  repeated Cluster clusters = 1;
+  bytes version_info = 1;
+  repeated Cluster clusters = 2;
 }
 
 // Circuit breaking settings can be specified individually for each defined

api/eds.proto

@@ -66,8 +66,12 @@ service EndpointDiscoveryService {
 }
 
 message EndpointDiscoveryRequest {
-  repeated string cluster_name = 1;
-  Node node = 2;
+  // The version_info provided in the request messages will be the version_info
+  // received with the most recent successfully processed response or empty on
+  // the first request.
+  bytes version_info = 1;
+  repeated string cluster_name = 2;
+  Node node = 3;
 }
 
 message LbEndpoint {
@@ -107,7 +111,8 @@ message LocalityLbEndpoints {
 }
 
 message EndpointDiscoveryResponse {
-  repeated ClusterLoadAssignment cluster_endpoints = 1;
+  bytes version_info = 1;
+  repeated ClusterLoadAssignment cluster_endpoints = 2;
 }
 
 // Example load report from a single request:
@@ -173,7 +178,11 @@ message ClusterStats {
 }
 
 message LoadAssignmentRequest {
-  Node node = 1;  // zone/region where this Envoy runs
+  // The version_info provided in the request messages will be the version_info
+  // received with the most recent successfully processed response or empty on
+  // the first request.
+  bytes version_info = 1;
+  Node node = 2;  // zone/region where this Envoy runs
   repeated ClusterStats cluster_stats = 3;
 }
 
@@ -204,7 +213,8 @@ message ClusterLoadAssignment {
 }
 
 message LoadAssignmentResponse {
-  repeated ClusterLoadAssignment clusters = 1;
+  bytes version_info = 1;
+  repeated ClusterLoadAssignment clusters = 2;
   // The default is 10 seconds.
-  google.protobuf.Duration load_reporting_interval = 2;
+  google.protobuf.Duration load_reporting_interval = 3;
 }

api/lds.proto

@@ -19,8 +19,9 @@ import "google/protobuf/wrappers.proto";
 // consist of a complete update of all listeners. Existing connections will be
 // allowed to drain from listeners that are no longer present.
 service ListenerDiscoveryService {
-  rpc StreamListeners(ListenerDiscoveryRequest) returns
-      (stream ListenerDiscoveryResponse) {}
+  rpc StreamListeners(stream ListenerDiscoveryRequest)
+      returns (stream ListenerDiscoveryResponse) {
+  }
 
   rpc FetchListeners(ListenerDiscoveryRequest)
       returns (ListenerDiscoveryResponse) {
@@ -32,11 +33,16 @@ service ListenerDiscoveryService {
 }
 
 message ListenerDiscoveryRequest {
-  Node node = 1;
+  // The version_info provided in the request messages will be the version_info
+  // received with the most recent successfully processed response or empty on
+  // the first request.
+  bytes version_info = 1;
+  Node node = 2;
 }
 
 message ListenerDiscoveryResponse {
-  repeated Listener listeners = 1;
+  bytes version_info = 1;
+  repeated Listener listeners = 2;
 }
 
 message Filter {

api/rds.proto

@@ -13,7 +13,7 @@ import "google/protobuf/duration.proto";
 import "google/protobuf/wrappers.proto";
 
 service RouteDiscoveryService {
-  rpc StreamRoutes(RouteDiscoveryRequest)
+  rpc StreamRoutes(stream RouteDiscoveryRequest)
       returns (stream RouteDiscoveryResponse) {
   }
 
@@ -27,16 +27,21 @@ service RouteDiscoveryService {
 }
 
 message RouteDiscoveryRequest {
-  Node node = 1;
+  // The version_info provided in the request messages will be the version_info
+  // received with the most recent successfully processed response or empty on
+  // the first request.
+  bytes version_info = 1;
+  Node node = 2;
   // The name of the route configuration. This allows an Envoy configuration
   // with multiple HTTP listeners (and associated HTTP connection manager
   // filters) to use different route configurations. Each listener will bind its
   // HTTP connection manager filter to a route table via this identifier.
-  string route_config_name = 2;
+  string route_config_name = 3;
 }
 
 message RouteDiscoveryResponse {
-  RouteConfiguration route_table = 1;
+  bytes version_info = 1;
+  RouteConfiguration route_table = 2;
 }
 
 // Compared to the cluster field that specifies a single upstream cluster as the