使用gridfsbucket opendownloadstream时出现“找不到文件”错误

我可以使用gridfsbucket的opendownloadstream上传一个文件,并在songs.files块下看到该文件。但出于某种原因,在尝试下载时会出现以下错误-

Caught exception: Error: FileNotFound: file def1.txt was not found

我的代码是-

var express = require('express');
var gridModule = express.Router();
var mongoose = require('mongoose');
var fs = require('fs');

gridModule.post('/', (req, res) => {
    console.log("::::grid");
    //const gridfs = new mongoose.mongo.GridFSBucket(mongoose.connection.db);

    //const writeStream = gridfs.openUploadStream('test.dat');

    var gridfs = new mongoose.mongo.GridFSBucket(mongoose.connection.db, {
        chunkSizeBytes: 1024,
        bucketName: 'songs'
    });

    fs.createReadStream('./def.txt').
        pipe(gridfs.openUploadStream('def1.txt')).
        on('error', function (error) {
            assert.ifError(error);
        }).
        on('finish', function () {
            console.log('done!');
            process.exit(0);
        });

});

gridModule.get('/', (req, res) => {
    var gridfs = new mongoose.mongo.GridFSBucket(mongoose.connection.db, {
        chunkSizeBytes: 1024,
        bucketName: 'songs'
    });
    /* var bucket = new mongodb.GridFSBucket(db, {
        chunkSizeBytes: 1024,
        bucketName: 'songs'
      }); */

      gridfs.openDownloadStream('def1.txt').
        pipe(fs.createWriteStream('./def1.txt')).
        on('error', function(error) {
            console.log(":::error");
          assert.ifError(error);
        }).
        on('finish', function() {
          console.log('done!');
          process.exit(0);
        });
});

module.exports = gridModule;

我也尝试使用objectid id,但同样的错误。有人猜到我在这里做错了什么吗?

注意-这里的代码可能不像声明两次bucket那样优化,请暂时忽略它,因为一旦它起作用,我将更正它。