Merge pull request #176 from pingww/main

clean offset
diff --git a/mqtt-cs/src/main/java/org/apache/rocketmq/mqtt/cs/session/loop/SessionLoopImpl.java b/mqtt-cs/src/main/java/org/apache/rocketmq/mqtt/cs/session/loop/SessionLoopImpl.java
index d37dd99..560fc52 100644
--- a/mqtt-cs/src/main/java/org/apache/rocketmq/mqtt/cs/session/loop/SessionLoopImpl.java
+++ b/mqtt-cs/src/main/java/org/apache/rocketmq/mqtt/cs/session/loop/SessionLoopImpl.java
@@ -523,6 +523,9 @@
     private void persistAllOffset(boolean needSleep) {
         try {
             for (Session session : sessionMap.values()) {
+                if (session.isClean()) {
+                    continue;
+                }
                 if (persistOffset(session) && needSleep) {
                     Thread.sleep(5L);
                 }
@@ -534,6 +537,9 @@
 
     private boolean persistOffset(Session session) {
         try {
+            if (session.isClean()) {
+                return true;
+            }
             if (!session.getPersistOffsetFlag()) {
                 return false;
             }