PLT-2899 adding clustering of app servers (#3682)

* PLT-2899 adding clustering of app servers

* PLT-2899 base framework

* PLT-2899 HA backend

* PLT-2899 Fixing config file

* PLT-2899 adding config syncing

* PLT-2899 set System console to readonly when clustering enabled.

* PLT-2899 Fixing publish API

* PLT-2899 fixing strings

einterfaces/cluster.go

@@ -0,0 +1,32 @@
+// Copyright (c) 2015 Mattermost, Inc. All Rights Reserved.
+// See License.txt for license information.
+
+package einterfaces
+
+import (
+	"github.com/mattermost/platform/model"
+)
+
+type ClusterInterface interface {
+	StartInterNodeCommunication()
+	StopInterNodeCommunication()
+	GetClusterInfos() []*model.ClusterInfo
+	RemoveAllSessionsForUserId(userId string)
+	InvalidateCacheForUser(userId string)
+	InvalidateCacheForChannel(channelId string)
+	Publish(event *model.WebSocketEvent)
+	UpdateStatus(status *model.Status)
+	GetLogs() ([]string, *model.AppError)
+	GetClusterId() string
+	ConfigChanged(previousConfig *model.Config, newConfig *model.Config, sendToOtherServer bool) *model.AppError
+}
+
+var theClusterInterface ClusterInterface
+
+func RegisterClusterInterface(newInterface ClusterInterface) {
+	theClusterInterface = newInterface
+}
+
+func GetClusterInterface() ClusterInterface {
+	return theClusterInterface
+}