Multer Azure Blob Storage

ES6 & Typescript friendly Multer storage engine for Azure's blob storage.

Installation

npm i -S multer-azure-blob-storage

or

yarn add multer-azure-blob-storage

Usage

Typescript

Leverages strong typings

import * as multer from 'multer';
import { MulterAzureStorage, MASNameResolver } from 'multer-azure-blob-storage';

const resolveBlobName: MASNameResolver = (req: any, file: Express.Multer.File): Promise<string> => {
    return new Promise<string>((resolve, reject) => {
        const blobName: string = yourCustomLogic(req, file);
        resolve(blobName);
    });
};

export type MetadataObj = { [k: string]: string };
const resolveMetadata: MASObjectResolver = (req: any, file: Express.Multer.File): Promise<MetadataObj> => {
    return new Promise<MetadataObj>((resolve, reject) => {
        const metadata: MetadataObj = yourCustomLogic(req, file);
        resolve(metadata);
    });
};

const azureStorage: MulterAzureStorage = new MulterAzureStorage({
    connectionString: 'DefaultEndpointsProtocol=https;AccountName=mystorageaccountname;AccountKey=wJalrXUtnFEMI/K7MDENG/bPxRfiCYzEXAMPLEKEY;EndpointSuffix=core.windows.net',
    accessKey: 'wJalrXUtnFEMI/K7MDENG/bPxRfiCYzEXAMPLEKEY',
    accountName: 'mystorageaccountname',
    containerName: 'documents',
    blobName: resolveBlobName,
    metadata: resolveMetadata,
    containerAccessLevel: 'blob'
});

const upload: multer.Instance = multer({
    storage: azureStorage
});

app.post('/documents', upload.any(), (req: Request, res: Response, next: NextFunction) => {
  console.log(req.files)
  res.status(200).json(req.files)
});

Javascript ES6

Common.js style imports

const multer = require('multer')
const MulterAzureStorage = require('multer-azure-blob-storage').MulterAzureStorage;

E6 style imports

import * as multer from 'multer';
import { MulterAzureStorage } from 'multer-azure-blob-storage';

Rest of the JS code

const resolveBlobName = (req, file) => {
    return new Promise((resolve, reject) => {
        const blobName = yourCustomLogic(req, file);
        resolve(blobName);
    });
};

const resolveMetadata = (req, file) => {
    return new Promise((resolve, reject) => {
        const metadata = yourCustomLogic(req, file);
        resolve(metadata);
    });
};

const azureStorage = new MulterAzureStorage({
    connectionString: 'DefaultEndpointsProtocol=https;AccountName=mystorageaccountname;AccountKey=wJalrXUtnFEMI/K7MDENG/bPxRfiCYzEXAMPLEKEY;EndpointSuffix=core.windows.net',
    accessKey: 'wJalrXUtnFEMI/K7MDENG/bPxRfiCYzEXAMPLEKEY',
    accountName: 'mystorageaccountname',
    containerName: 'documents',
    blobName: resolveBlobName,
    metadata: resolveMetadata,
    containerAccessLevel: 'blob'
});

const upload = multer({
    storage: azureStorage
});

app.post('/documents', upload.any(), (req, res, next) => {
  console.log(req.files)
  res.status(200).json(req.files)
});

More details on using upload can be found in the Multer documentation

File information

Multer Azure Blob Storage will return the following information in each file uploaded. This can be found in the req.files param:

Key	Description	Note
fieldname	The field name/key sent in the form's post request.	Added by Multer
originalname	Full original name of the file on the user's computer.	Added by Multer
encoding	File encoding type.	Added by Multer
mimetype	MIME type of the file.	Added by Multer
blobName	Blob/file name of created blob in Azure storage.
containerName	Name of azure storage container where the blob/file was uploaded to.
blobType	Type of blob.	From the result of call to azure's getBlobProperties() of blobService
size	Size of the blob.	From the result of call to azure's getBlobProperties() of blobService
etag	Etag.	From the result of call to azure's getBlobProperties() of blobService
metadata	Blob's metadata.	From the result of call to azure's getBlobProperties() of blobService
url	The full url to access the uploaded blob/file.

Configuration object

Details of the configuration object that needs to be passed into the constructor of the MulterAzureStorage class.

Parameter Name	Type	Sample Value
connectionString	string	'DefaultEndpointsProtocol=https;AccountName=mystorageaccountname;AccountKey=wJalrXUtnFEMI/K7MDENG/bPxRfiCYzEXAMPLEKEY;EndpointSuffix=core.windows.net'
accessKey	string	'wJalrXUtnFEMI/K7MDENG/bPxRfiCYzEXAMPLEKEY'
accountName	string	'mystorageaccountname'
containerName	string or function: MASNameResolver	'documents' or (req: any, file: Express.Multer.File) => Promise<string>
metadata	{ [k: string]: string } or function: MASObjectResolver	'{author: John Doe; album: ASOT}' or (req: any, file: Express.Multer.File) => Promise<{[k: string]: string}>
blobName	function: MASNameResolver (optional)	(req: any, file: Express.Multer.File) => Promise<string>
containerAccessLevel	string (optional)	'blob' or 'container' or 'private'
urlExpirationTime	number (optional)	60

For more information about the meaning of individual parameters please check Azure documentation on node.js integration.

Defaults

For the optional parameters in the configuration object for the MulterAzureStorage class, here are the default fallbacks:

• containerAccessLevel: blob
• urlExpirationTime: 60 minutes. NOTE: To unset this property and not revert to the default, pass in -1
• blobName: Date.now() + '-' + uuid.v4() + path.extname(file.originalname). This results in a url safe filename that looks like '1511161727560-d83d24c8-d213-444c-ba72-316c7a858805.png'

File naming

The containerName can be anything you choose, as long as it's unique to the storage account and as long as it fits Azure's naming restrictions. If the container does not exist the storage engine will create it.

The blobName in an Azure container also needs to have a unique name.

multer-azure-blob-storage allows you to customize the containerName and blobName per request before uploading the file. This can be done by providing a MASNameResolver function in the configuration object for the desired parameter.

const resolveName: MASNameResolver = (req: any, file: Express.Multer.File): Promise<string> => {
    return new Promise<string>((resolve, reject) => {
        // Compute containerName or blobName with your custom logic.
        const computedName: string = yourCustomLogic(req, file);
        resolve(computedName);
    });
};

multer-azure-blob-storage also allows you to add/customize metadata per request before uploading the file. This can be done by providing a MASObjectResolver function in the configuration object for the desired parameter.

export type MetadataObj = { [k: string]: string };
const resolveMetadata: MASObjectResolver = (req: any, file: Express.Multer.File): Promise<MetadataObj> => {
    return new Promise<MetadataObj>((resolve, reject) => {
        const metadata: MetadataObj = yourCustomLogic(req, file);
        resolve(metadata);
    });
};

Azure

Creating a storage account

For instructions on how to create a storage account, see the following Azure documentation.

Credentials (Quick tips)

Your credentials can all be obtained under the Access keys section in the storage account pane in Azure.

The connectionString is prefered. If its not provides, please provide accessKey and accountName.

You only need to provide one of the two access keys in the accessKey field.

The accountName is just the name of your storage account that you've created in Azure.

If using the MulterAzureStorage class without passing in any configuration options then the following environment variables will need to be set:

1. AZURE_STORAGE_CONNECTION_STRING, for the connectionString.
2. AZURE_STORAGE_ACCESS_KEY, for the accessKey.
3. AZURE_STORAGE_ACCOUNT, for the accountName.

Tests

Not implemented yet

Thanks

All great things are built on the shoulder of giants. I want to thank my giants for lending their shoulders:

• mckalexee
• MantaCodeDevs

License

MIT