PLT-4357 adding performance monitoring (#4622)

* WIP

* WIP

* Adding metrics collection

* updating vendor packages

* Adding metrics to config

* Adding admin console page for perf monitoring

* Updating glide

* switching to tylerb/graceful

api/web_conn.go

@@ -7,6 +7,7 @@ import (
 	"fmt"
 	"time"
 
+	"github.com/mattermost/platform/einterfaces"
 	"github.com/mattermost/platform/model"
 	"github.com/mattermost/platform/utils"
 
@@ -111,6 +112,12 @@ func (c *WebConn) writePump() {
 				return
 			}
 
+			if msg.EventType() == model.WEBSOCKET_EVENT_POSTED {
+				if einterfaces.GetMetricsInterface() != nil {
+					einterfaces.GetMetricsInterface().IncrementPostBroadcast()
+				}
+			}
+
 		case <-ticker.C:
 			c.WebSocket.SetWriteDeadline(time.Now().Add(WRITE_WAIT))
 			if err := c.WebSocket.WriteMessage(websocket.PingMessage, []byte{}); err != nil {