VOL-4019: Initial commit with grpc nbi, sbi, etcd, kafka and hw management rpcs.

Change-Id: I78feaf7da284028fc61f42c5e0c5f56e72fe9e78
diff --git a/pkg/nbi/common.go b/pkg/nbi/common.go
new file mode 100644
index 0000000..4f80e8c
--- /dev/null
+++ b/pkg/nbi/common.go
@@ -0,0 +1,92 @@
+/*
+ * Copyright 2020-present Open Networking Foundation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+// Package nbi holds rpc server apis implemented
+package nbi
+
+import (
+	"context"
+	"net"
+	"os"
+
+	"github.com/opencord/opendevice-manager/pkg/config"
+
+	"github.com/opencord/device-management-interface/go/dmi"
+
+	"github.com/opencord/voltha-lib-go/v4/pkg/log"
+	g "google.golang.org/grpc"
+	"google.golang.org/grpc/credentials"
+	"google.golang.org/grpc/reflection"
+)
+
+// logger represents the log object
+var logger log.CLogger
+
+// grpcServer refers to object which holds grpc serevr
+var grpcServer *g.Server
+
+// init function for the package
+func init() {
+	logger = config.Initlog()
+	initConnectMap()
+}
+
+func registerServers(grpcServer *g.Server) {
+	hwMgmtSvc := new(NativeHwManagementService)
+	dmi.RegisterNativeHWManagementServiceServer(grpcServer, hwMgmtSvc)
+	reflection.Register(grpcServer)
+}
+
+// StartGrpcServer starts the grpc server for listening to NEM requests
+func StartGrpcServer(ctx context.Context) {
+	coreFlags := config.GetCoreFlags()
+	lis, err := net.Listen("tcp", coreFlags.GrpcEndPoint)
+	if err != nil {
+		logger.Error(ctx, "Failed-to-listen-on-Grpc-Port", log.Fields{"grpc-flags": coreFlags.GrpcFlags, "error": err})
+		os.Exit(1)
+	}
+
+	if coreFlags.SecureConnection {
+		creds, err := credentials.NewServerTLSFromFile(coreFlags.ServerCrt, coreFlags.ServerKey)
+		if err != nil {
+			logger.Error(ctx, "could-not-process-the-credentials", log.Fields{"error": err})
+		}
+		grpcServer = g.NewServer(g.Creds(creds))
+	} else {
+		grpcServer = g.NewServer()
+	}
+
+	registerServers(grpcServer)
+
+	logger.Infow(ctx, "Grpc-server-starting", log.Fields{"grpc-server-info": grpcServer, "grpc-env-info": coreFlags.GrpcFlags, "is-secure-conn": coreFlags.SecureConnection})
+
+	// Starting the server
+	if err := grpcServer.Serve(lis); err != nil {
+		logger.Errorw(ctx, "Failed-to-start-Grpc-Server", log.Fields{"server": coreFlags.GrpcFlags, "error": err})
+		os.Exit(1)
+	}
+
+	logger.Infow(ctx, "grpc-server-stopped-successfully", log.Fields{"grpc-server-info": grpcServer, "grpc-env-info": coreFlags.GrpcFlags})
+
+}
+
+// StopGrpcServer tear down the gRPC connection from opendevice manager to NEM
+func StopGrpcServer(ctx context.Context) {
+	if grpcServer != nil {
+		grpcServer.GracefulStop()
+	}
+	logger.Infow(ctx, "grpc-server-teardown-success", log.Fields{"grpc-server-info": grpcServer})
+}