diff --git a/core/group_chat.go b/core/group_chat.go
index 97a53f5..0fcbaa1 100644
--- a/core/group_chat.go
+++ b/core/group_chat.go
@@ -1,6 +1,7 @@
 package core
 
 import (
+	"encoding/gob"
 	"encoding/json"
 	"fmt"
 	"net/http"
@@ -38,6 +39,10 @@ type groupChat struct {
 	sendUpstreamMessage func(msg *wshandler.UpstreamMessage)
 }
 
+func init() {
+	gob.Register(map[string]string{})
+}
+
 func (gc *groupChat) Initialize(tv *Tavern, cfg configDocument) error {
 	rem, _ := json.Marshal(cfg)
 	if err := json.Unmarshal(rem, &gc.chatConfig); err != nil {
@@ -122,7 +127,6 @@ func (gc *groupChat) ClientDisconnected(msg string, callby *wshandler.Sender) {
 		if typename == "public" {
 			cnt, err := gc.rh.JSONDel(chanid, "$.members."+callby.Alias)
 			if cnt > 0 {
-				gc.rh.JSONNumIncrBy(chanid, "$.size", -1)
 				if cfg, ok := gc.chatConfig.Channels[chanid]; ok {
 					cfg.inoutChan <- "-" + callby.Alias
 				}
@@ -151,14 +155,13 @@ func (gc *groupChat) EnterPublicChannel(ctx wshandler.ApiCallContext) {
 		return
 	}
 
-	atomicsize, _ := gc.rh.JSONNumIncrBy(chanid, "$.size", 1)
+	atomicsize, _ := gc.rh.JSONObjLen(chanid, "$.members")
 	if len(atomicsize) == 0 {
 		return
 	}
 
-	if atomicsize[0] > cfg.Capacity {
-		logger.Println("chatting channel is full :", chanid, atomicsize[0]-1, cfg.Capacity)
-		gc.rh.JSONNumIncrBy(chanid, "$.size", -1)
+	if atomicsize[0] >= cfg.Capacity {
+		logger.Println("chatting channel is full :", chanid, atomicsize[0], cfg.Capacity)
 		return
 	}
 
@@ -181,7 +184,6 @@ func (gc *groupChat) EnterPublicChannel(ctx wshandler.ApiCallContext) {
 		return
 	}
 
-	logger.Println("groupchat EnterPublicChannel JSONSet :", chanid, ctx.CallBy.Alias)
 	gc.enterRoom(chanid, ctx.CallBy.Accid)
 	cfg.inoutChan <- "+" + ctx.CallBy.Alias
 
@@ -210,8 +212,6 @@ func (gc *groupChat) LeavePublicChannel(ctx wshandler.ApiCallContext) {
 
 		cnt, err := gc.rh.JSONDel(oldchan, "$.members."+ctx.CallBy.Alias)
 		if cnt > 0 {
-			gc.rh.JSONNumIncrBy(oldchan, "$.size", -1)
-			logger.Println("groupchat LeavePublicChannel JSONDel :", oldchan, ctx.CallBy.Alias)
 			gc.leaveRoom(oldchan, ctx.CallBy.Accid)
 			if cfg, ok := gc.chatConfig.Channels[oldchan]; ok {
 				cfg.inoutChan <- "-" + ctx.CallBy.Alias