Multer S3

Streaming multer storage engine for AWS S3.

This project is mostly an integration piece for existing code samples from Multer's storage engine documentation with s3fs as the substitution piece for file system. Existing solutions I found required buffering the multipart uploads into the actual filesystem which is difficult to scale.

Installation

npm install --save multer-s3

Usage

var aws = require('aws-sdk')
var express = require('express')
var multer = require('multer')
var multerS3 = require('multer-s3')

var app = express()
var s3 = new aws.S3({ /* ... */ })

var upload = multer({
  storage: multerS3({
    s3: s3,
    bucket: 'some-bucket',
    metadata: function (req, file, cb) {
      cb(null, {fieldName: file.fieldname});
    },
    key: function (req, file, cb) {
      cb(null, Date.now().toString())
    }
  })
})

app.post('/upload', upload.array('photos', 3), function(req, res, next) {
  res.send('Successfully uploaded ' + req.files.length + ' files!')
})

File information

Each file contains the following information exposed by multer-s3:

Key	Description	Note
`size`	Size of the file in bytes
`bucket`	The bucket used to store the file	`S3Storage`
`key`	The name of the file	`S3Storage`
`acl`	Access control for the file	`S3Storage`
`contentType`	The `mimetype` used to upload the file	`S3Storage`
`metadata`	The `metadata` object to be sent to S3	`S3Storage`
`location`	The S3 `url` to access the file	`S3Storage`
`etag`	The `etag`of the uploaded file in S3	`S3Storage`

Setting ACL

ACL values can be set by passing an optional acl parameter into the multerS3 object.

var upload = multer({
  storage: multerS3({
    s3: s3,
    bucket: 'some-bucket',
    acl: 'public-read',
    key: function (req, file, cb) {
      cb(null, Date.now().toString())
    }
  })
})

Available options for canned ACL.

ACL Option	Permissions added to ACL
`private`	Owner gets `FULL_CONTROL`. No one else has access rights (default).
`public-read`	Owner gets `FULL_CONTROL`. The `AllUsers` group gets `READ` access.
`public-read-write`	Owner gets `FULL_CONTROL`. The `AllUsers` group gets `READ` and `WRITE` access. Granting this on a bucket is generally not recommended.
`aws-exec-read`	Owner gets `FULL_CONTROL`. Amazon EC2 gets `READ` access to `GET` an Amazon Machine Image (AMI) bundle from Amazon S3.
`authenticated-read`	Owner gets `FULL_CONTROL`. The `AuthenticatedUsers` group gets `READ` access.
`bucket-owner-read`	Object owner gets `FULL_CONTROL`. Bucket owner gets `READ` access. If you specify this canned ACL when creating a bucket, Amazon S3 ignores it.
`bucket-owner-full-control`	Both the object owner and the bucket owner get `FULL_CONTROL` over the object. If you specify this canned ACL when creating a bucket, Amazon S3 ignores it.
`log-delivery-write`	The `LogDelivery` group gets `WRITE` and `READ_ACP` permissions on the bucket. For more information on logs.

Setting Metadata

The metadata option is a callback that accepts the request and file, and returns a metadata object to be saved to S3.

Here is an example that stores all fields in the request body as metadata, and uses an id param as the key:

var opts = {
    s3: s3,
    bucket: config.originalsBucket,
    metadata: function (req, file, cb) {
      cb(null, Object.assign({}, req.body));
    },
    key: function (req, file, cb) {
      cb(null, req.params.id + ".jpg");
    }
  };

Setting Cache-Control header

The optional cacheControl option sets the Cache-Control HTTP header that will be sent if you're serving the files directly from S3. You can pass either a string or a function that returns a string.

Here is an example that will tell browsers and CDNs to cache the file for one year:

var upload = multer({
  storage: multerS3({
    s3: s3,
    bucket: 'some-bucket',
    cacheControl: 'max-age=31536000',
    key: function (req, file, cb) {
      cb(null, Date.now().toString())
    }
  })
})

Setting Custom Content-Type

The optional contentType option can be used to set Content/mime type of the file. By default the content type is set to application/octet-stream. If you want multer-s3 to automatically find the content-type of the file, use the multerS3.AUTO_CONTENT_TYPE constant. Here is an example that will detect the content type of the file being uploaded.

var upload = multer({
  storage: multerS3({
    s3: s3,
    bucket: 'some-bucket',
    contentType: multerS3.AUTO_CONTENT_TYPE,
    key: function (req, file, cb) {
      cb(null, Date.now().toString())
    }
  })
})

You may also use a function as the contentType, which should be of the form function(req, file, cb).

Testing

The tests mock all access to S3 and can be run completely offline.

npm test

hetenho/multer-s3