diff --git a/apps/applications/utils/db_port_mapper.py b/apps/applications/utils/db_port_mapper.py
index 321751148..0b6bdd93a 100644
--- a/apps/applications/utils/db_port_mapper.py
+++ b/apps/applications/utils/db_port_mapper.py
@@ -29,20 +29,6 @@ class DBPortManager(object):
         mapper = dict(zip(self.all_usable_ports, list(db_ids)))
         self.set_mapper(mapper)
 
-    def get_db_by_port(self, port):
-        mapper = self.get_mapper()
-        db_id = mapper.get(port, None)
-        if db_id:
-            db = get_object_or_none(Application, id=db_id)
-            if not db:
-                msg = 'Database not exists, database id: {}'.format(db_id)
-            else:
-                msg = ''
-        else:
-            db = None
-            msg = 'Port not in port-db mapper, port: {}'.format(port)
-        return db, msg
-
     def add(self, db: Application):
         mapper = self.get_mapper()
         usable_port = self.get_next_usable_port()
@@ -54,25 +40,41 @@ class DBPortManager(object):
 
     def pop(self, db: Application):
         mapper = self.get_mapper()
-        to_delete_port = None
-        for port, db_id in mapper.items():
-            if db_id == str(db.id):
-                to_delete_port = port
-                break
+        to_delete_port = self.get_port_by_db(db)
         mapper.pop(to_delete_port, None)
         self.set_mapper(mapper)
 
+    def get_port_by_db(self, db):
+        mapper = self.get_mapper()
+        for port, db_id in mapper.items():
+            if db_id == str(db.id):
+                return port
+
+    def get_db_by_port(self, port):
+        mapper = self.get_mapper()
+        db_id = mapper.get(port, None)
+        if db_id:
+            db = get_object_or_none(Application, id=db_id)
+            if not db:
+                msg = 'Database not exists, database id: {}'.format(db_id)
+            else:
+                msg = ''
+        else:
+            db = None
+            msg = 'Port not in port-db mapper, port: {}'.format(port)
+        return db, msg
+
     def get_next_usable_port(self):
         already_use_ports = self.get_already_use_ports()
         usable_ports = list(set(self.all_usable_ports) - set(already_use_ports))
         if len(usable_ports) > 1:
             return usable_ports[0]
-        else:
-            already_use_ports = self.get_already_use_ports()
-            msg = 'No port is usable, All usable port count: {}, Already use port count: {}'.format(
-                len(self.all_usable_ports), len(already_use_ports)
-            )
-            logger.warning(msg)
+
+        already_use_ports = self.get_already_use_ports()
+        msg = 'No port is usable, All usable port count: {}, Already use port count: {}'.format(
+            len(self.all_usable_ports), len(already_use_ports)
+        )
+        logger.warning(msg)
 
     def get_already_use_ports(self):
         mapper = self.get_mapper()
@@ -82,6 +84,11 @@ class DBPortManager(object):
         return cache.get(self.CACHE_KEY, {})
 
     def set_mapper(self, value):
+        """
+        value: {
+            port: db_id
+        }
+        """
         cache.set(self.CACHE_KEY, value, timeout=None)