node在操作gridfs时出了错，求解答

异常: MongoError: cannot establish topology capabilities as driver is still in process of connecting

var mongodb = require('mongodb');
var db = new mongodb.Db('image_test', new mongodb.Server('127.0.0.1', 27017));

var ImageDB = {
    'save_image': function(img, callback){
        var gs = new mongodb.GridStore(db, name, 'w',{
            'content_type' : img.mimetype
        });
        gs.open(function(err, gs){
            gs.write(img.buffer, function(){
                gs.close(function(err, result){
                    if(err){
                        console.log(err);
                    }else{
                        console.log(result);
                    }
                });
            });
        });
    },
}

请问这何解，今天刚学node

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已经解决了。。。原来还需要先open一下。。。明天再研究了

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你好，能分享一下你的完整代码吗？