Multer's GridFS storage engine

GridFS storage engine for Multer to store uploaded files directly to MongoDb.

This module is intended to be used with the v1.x branch of Multer.

The new version 2 brings a simplified api and more features. If you still need the old version, you can switch to the v1.x branch.

Installation

Using npm

$ npm install multer-gridfs-storage --save

Basic usage example:

const express = require('express');
const multer  = require('multer');

// Create a storage object with a given configuration
const storage = require('multer-gridfs-storage')({
   url: 'mongodb://yourhost:27017/database'
});

// Set multer storage engine to the newly created object
const upload = multer({ storage: storage });

const app = express()

// Upload your files as usual
const sUpload = upload.single('avatar');
app.post('/profile', sUpload, (req, res, next) => { 
    /*....*/ 
})

const arrUpload = upload.array('photos', 12);
app.post('/photos/upload', arrUpload, (req, res, next) => {
    /*....*/ 
})

const fUpload = upload.fields([{ name: 'avatar', maxCount: 1 }, { name: 'gallery', maxCount: 8 }])
app.post('/cool-profile', fUpload, (req, res, next) => {
    /*....*/ 
})

API

module(options): function

The module returns a function that can be invoked with options to create a Multer storage engine.

Check the wiki for an in depth guide on how to use this module.

Options

The options parameter is an object with the following properties.

url

Type: string

Required if db option is not present

The mongodb connection uri.

A string pointing to the database used to store the incoming files. This must be a standard mongodb connection string.

With this option the module will create a mongodb connection for you instead.

Note: If the db option is specified this setting is ignored.

Example:

const storage = require('multer-gridfs-storage')({
    url: 'mongodb://yourhost:27017/database'
});

connectionOpts

Type: object

Not required

This setting allows you to customize how this module establishes the connection if you are using the url option.

You can set this to an object like is specified in the MongoClient.connect documentation and change the default behavior without having to create the connection yourself using the db option.

db

Type: DB or Promise

Required if url option is not present

The database connection to use or a promise that resolves with the connection.

This is useful to reuse an existing connection to create more storage objects.

Example:

MongoClient.connect('mongodb://yourhost:27017/database').then((database) => {
  storage = new GridFSStorage({ db: database });
});

or

const promise = MongoClient.connect('mongodb://yourhost:27017/database');
storage = new GridFSStorage({ db: promise });

file

Type: function or function*

Not required

A function to control the file storage in the database. Is invoked per file with the parameters req and file, in that order.

By default, this module behaves exactly like the default Multer disk storage does. It generates a 16 bytes long name in hexadecimal format with no extension for the file to guarantee that there are very low probabilities of naming collisions. You can override this by passing your own function.

The return value of this function is an object or a promise that resolves to an object (this also applies to generators) with the following properties.

Any missing properties will use the defaults.

If you return null or undefined from the file function, the values for the current file will also be the defaults. This is useful when you want to conditionally change some files while leaving others untouched.

This example will use the collection 'photos' only for incoming files whose reported mime-type is image/jpeg, the others will be stored using default values.

const GridFsStorage = require('multer-gridfs-storage');

const storage = new GridFsStorage({
  url: 'mongodb://host:27017/database',
  file: (req, file) => {
    if (file.mimetype === 'image/jpeg') {
      return {
        bucketName: 'photos'
      };
    } else {
      return null;
    }
  }
});
const upload = multer({ storage });

This other example names every file something like 'file_1504287812377', using the date to change the number and to generate unique values

const GridFsStorage = require('multer-gridfs-storage');

const storage = new GridFsStorage({
  url: 'mongodb://host:27017/database',
  file: (req, file) => {
    return {
      filename: 'file_' + Date.now()
    };
  }
});
const upload = multer({ storage });

Is also possible to return values other than objects, like strings or numbers, in which case they will be used as the filename and the remaining properties will use the defaults. This is a simplified version of a previous example

const GridFsStorage = require('multer-gridfs-storage');

const storage = new GridFsStorage({
  url: 'mongodb://host:27017/database',
  file: (req, file) => {
    // instead of an object a string is returned
    return 'file_' + Date.now();
  }
});
const upload = multer({ storage });

Internally the function crypto.randomBytes is used to generate names. In this example, files are named using the same format plus the extension as received from the client, also changing the collection where to store files to uploads

const crypto = require('crypto');
const path = require('path');
const GridFsStorage = require('multer-gridfs-storage');

var storage = new GridFsStorage({
  url: 'mongodb://host:27017/database',
  file: (req, file) => {
    return new Promise((resolve, reject) => {
      crypto.randomBytes(16, (err, buf) => {
        if (err) {
          return reject(err);
        }
        const filename = buf.toString('hex') + path.extname(file.originalname));
        const fileInfo = {
          filename: filename,
          bucketName: 'uploads'
        };
        resolve(fileInfo);
      });
    });
  }
});
const upload = multer({ storage });

File information

Each file in req.file and req.files contain the following properties in addition to the ones that Multer create by default. Most of them can be set using the file configuration.

To see all the other properties of the file object, check the Multer's documentation.

Note:

Do not confuse contentType with Multer's mimetype. The first is the value in the database while the latter is the value in the request.

You could choose to override the value at the moment of storing the file. In most cases both values should be equal.

Events

Each storage object is also a standard Node.js Event Emitter. This is done to ensure that some internal events can also be handled in user code.

Event: 'connection'

This event is emitted when the MongoDb connection is ready to use.

Event arguments

• db: The MongoDb database object that holds the connection

This event is triggered at most once.

Event: 'connectionFailed'

This event is emitted when the connection could not be opened.

• err: The connection error

This event only triggers at most once.

Only one of the events connection or connectionFailed will be emitted.

Event: 'file'

This event is emitted every time a new file is stored in the db.

Event arguments

• file: The uploaded file

Event: 'streamError'

This event is emitted when there is an error streaming the file to the database.

Event arguments

• error: The streaming error
• conf: The failed file configuration

Note:

Previously this event was named error which seemed to be the most logical choice but unfortunately this introduces a problem:

In node.js error events are special and crash the process if an error is emitted and there is no error listener attached. You could choose to handle errors in an express middleware forcing you to set an empty error listener to avoid crashing.

To simplify the issue this event was renamed to allow you to choose the best way to handle storage errors.

Event: 'dbError'

This event is emitted when the underlying connection emits an error.

Only available when the storage is created with the url option.

Event arguments

• error: The error emitted by the database connection

Test

To run the test suite, first install the dependencies, then run npm test:

$ npm install
$ npm test

Tests are written with mocha and chai.

Code coverage thanks to istanbul

$ npm coverage

License

MIT