[VOL-4442] grpc streaming connection monitoring

Change-Id: Id787e94cf28745d36e72f8ed2f5c316312714db4
diff --git a/protos/voltha_protos/core_services.proto b/protos/voltha_protos/core_services.proto
index f0929f4..738bd3e 100755
--- a/protos/voltha_protos/core_services.proto
+++ b/protos/voltha_protos/core_services.proto
@@ -15,8 +15,10 @@
 // The CoreService is a gRPC service implemented by the Voltha RW-Core for the
 // sole purpose of serving requests/updates from the Voltha adapters. 
 service CoreService {
-	//	 in coreProxy interface
-	rpc GetHealthStatus(common.Connection) returns (health.HealthStatus);
+	// GetHealthStatus is used by a CoreService client to verify connectivity
+    // to the gRPC server hosting the CoreService service
+    rpc GetHealthStatus(stream common.Connection) returns (stream health.HealthStatus);
+
 	rpc RegisterAdapter (core_adapter.AdapterRegistration) returns (google.protobuf.Empty);
 	rpc DeviceUpdate (device.Device) returns (google.protobuf.Empty);
 	rpc PortCreated (device.Port) returns (google.protobuf.Empty);