VOL-1405 : First submission for read-only core

- Most of the logic was copied from the read-write implementation
- Added missing Get/List calls
- Added necessary targets in Makefile
- Added docker and k8s manifests

Amendments:

- Removed more unecessary code.
- Removed refs to kafka
- Adjustements to reflect comments
- Removed refs to kafka in manifests

Change-Id: Ife2ca13d3ae428923825f7c19d42359d60406839
diff --git a/ro_core/core/core.go b/ro_core/core/core.go
new file mode 100644
index 0000000..0ba9b1b
--- /dev/null
+++ b/ro_core/core/core.go
@@ -0,0 +1,134 @@
+/*
+ * Copyright 2018-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 core
+
+import (
+	"context"
+	grpcserver "github.com/opencord/voltha-go/common/grpc"
+	"github.com/opencord/voltha-go/common/log"
+	"github.com/opencord/voltha-go/db/kvstore"
+	"github.com/opencord/voltha-go/db/model"
+	"github.com/opencord/voltha-go/protos/voltha"
+	"github.com/opencord/voltha-go/ro_core/config"
+	"google.golang.org/grpc"
+)
+
+type Core struct {
+	instanceId        string
+	genericMgr        *ModelProxyManager
+	deviceMgr         *DeviceManager
+	logicalDeviceMgr  *LogicalDeviceManager
+	grpcServer        *grpcserver.GrpcServer
+	grpcNBIAPIHandler *APIHandler
+	config            *config.ROCoreFlags
+	clusterDataRoot   model.Root
+	localDataRoot     model.Root
+	clusterDataProxy  *model.Proxy
+	localDataProxy    *model.Proxy
+	exitChannel       chan int
+	kvClient          kvstore.Client
+}
+
+func init() {
+	log.AddPackage(log.JSON, log.DebugLevel, nil)
+}
+
+func NewCore(id string, cf *config.ROCoreFlags, kvClient kvstore.Client) *Core {
+	var core Core
+	core.instanceId = id
+	core.exitChannel = make(chan int, 1)
+	core.config = cf
+	core.kvClient = kvClient
+
+	// Setup the KV store
+	// Do not call NewBackend constructor; it creates its own KV client
+	// Commented the backend for now until the issue between the model and the KV store
+	// is resolved.
+	backend := model.Backend{
+		Client:     kvClient,
+		StoreType:  cf.KVStoreType,
+		Host:       cf.KVStoreHost,
+		Port:       cf.KVStorePort,
+		Timeout:    cf.KVStoreTimeout,
+		PathPrefix: "service/voltha"}
+	core.clusterDataRoot = model.NewRoot(&voltha.Voltha{}, &backend)
+	core.localDataRoot = model.NewRoot(&voltha.CoreInstance{}, &backend)
+	core.clusterDataProxy = core.clusterDataRoot.CreateProxy("/", false)
+	core.localDataProxy = core.localDataRoot.CreateProxy("/", false)
+	return &core
+}
+
+func (core *Core) Start(ctx context.Context) {
+	log.Info("starting-adaptercore", log.Fields{"coreId": core.instanceId})
+	core.genericMgr = newModelProxyManager(core.clusterDataProxy)
+	core.deviceMgr = newDeviceManager(core.clusterDataProxy, core.instanceId)
+	core.logicalDeviceMgr = newLogicalDeviceManager(core.deviceMgr, core.clusterDataProxy)
+	go core.startDeviceManager(ctx)
+	go core.startLogicalDeviceManager(ctx)
+	go core.startGRPCService(ctx)
+
+	log.Info("adaptercore-started")
+}
+
+func (core *Core) Stop(ctx context.Context) {
+	log.Info("stopping-adaptercore")
+	core.exitChannel <- 1
+	// Stop all the started services
+	core.grpcServer.Stop()
+	core.logicalDeviceMgr.stop(ctx)
+	core.deviceMgr.stop(ctx)
+	log.Info("adaptercore-stopped")
+}
+
+//startGRPCService creates the grpc service handlers, registers it to the grpc server
+// and starts the server
+func (core *Core) startGRPCService(ctx context.Context) {
+	//	create an insecure gserver server
+	core.grpcServer = grpcserver.NewGrpcServer(core.config.GrpcHost, core.config.GrpcPort, nil, false)
+	log.Info("grpc-server-created")
+
+	core.grpcNBIAPIHandler = NewAPIHandler(core.genericMgr, core.deviceMgr, core.logicalDeviceMgr)
+	core.logicalDeviceMgr.setGrpcNbiHandler(core.grpcNBIAPIHandler)
+	//	Create a function to register the core GRPC service with the GRPC server
+	f := func(gs *grpc.Server) {
+		voltha.RegisterVolthaServiceServer(
+			gs,
+			core.grpcNBIAPIHandler,
+		)
+	}
+
+	core.grpcServer.AddService(f)
+	log.Info("grpc-service-added")
+
+	//	Start the server
+	core.grpcServer.Start(context.Background())
+	log.Info("grpc-server-started")
+}
+
+func (core *Core) startDeviceManager(ctx context.Context) {
+	// TODO: Interaction between the logicaldevicemanager and devicemanager should mostly occur via
+	// callbacks.  For now, until the model is ready, devicemanager will keep a reference to the
+	// logicaldevicemanager to initiate the creation of logical devices
+	log.Info("starting-DeviceManager")
+	core.deviceMgr.start(ctx, core.logicalDeviceMgr)
+	log.Info("started-DeviceManager")
+}
+
+func (core *Core) startLogicalDeviceManager(ctx context.Context) {
+	log.Info("starting-Logical-DeviceManager")
+	core.logicalDeviceMgr.start(ctx)
+	log.Info("started-Logical-DeviceManager")
+}