 CacheManager           = require('./cache_manager')
 SystemPermissions      = require('./system_permissions')
 
-class UserPermissionManager extends CacheManager
+# the permission might be changed by other workers.
+# caching is disabled
+class UserPermissionManager
     collectionName = "Permissions"
 
     constructor : (@mongoInterface, callback) ->
-        super(SystemPermissions)
         @dbOperation('addIndex', null, {_email:1}, 
             (err) =>
                 callback(err,this)

                if sysPermRec
                    @dbOperation 'removeUser', user, null, (err) ->
                        # Remove from cache
                        next(err, @remove(user))
                else next(null, null)
        ], callback


                callback(null, null)
            else callback(null, sysPermRec)

        Async.waterfall [
            (next) =>
                @dbOperation('findUser', user, null, next)
            (dbRecord, next) =>
                if not dbRecord then next(null, null)
                else
                    # Add to cache
                    sysPermRec = new SystemPermissions(user, dbRecord.permission)
                    for mountPoint, app of dbRecord.apps
                        appPerm = sysPermRec.addItem(mountPoint, app.permission)
                        if app.appInstances
