Nodestream

Streaming library for binary data transfers

Description

This library aims to provide an abstraction layer between your application/library and all the various remote storage services which exist on the market, either as hosted by 3rd parties or self-hosted (S3, GridFS etc.). Your code should not depend on these services directly - the code responsible for uploading a file should remain the same no matter which storage service you decide to use. The only thing that can change is the configuration.

Available adapters


Amazon S3	GridFS (WIP)	Google Cloud Storage	Local Filesystem

Available transforms

See Transforms section for more info.

checksum	compress	progress (WIP)	crypto (WIP)
Checksum Calculator	Stream (de)compressor	Progress monitor	Stream (en/de)cryption

Usage

Installation

The first step is to install nodestream into your project:

npm install --save nodestream

The next thing is to decide which adapter you want to use. An adapter is an interface for nodestream to be able to interact with a particular storage system. Let's use local filesystem for a start:

npm install --save nodestream-filesystem

Configuration

Let's create and configure a nodestream instance with which your application can then interact:

// Require the main Nodestream class
const Nodestream = require('nodestream')
const nodestream = new Nodestream({
  // This tells nodestream which storage system it should interact with
  // Under the hood, it will try to require `nodestream-filesystem` module
  adapter: 'filesystem',
  // This object is always specific to your adapter of choice - always check
  // the documentation for that adapter for available options
  config: {
    // You MUST provide either an absolute path or nothing at all
    // You can use array notation, the parts will be joined for you
    root: [__dirname, '.storage']
  }
})

Great! At this point, nodestream is ready to transfer some bytes!

Actions

Uploading

You can upload any kind of readable stream. Nodestream does not care where that stream comes from, whether it's an http upload or a file from your filesystem or something totally different.

For this example, we will upload a file from our filesystem.

We will be uploading the file to our local filesystem as well as reading it from the same filesystem. Normally you would probably use a source different from the target storage, but Nodestream does not really care.

const fs = require('fs')
// This is the file we will upload - create a readable stream of that file
const profilePic = fs.createReadStream('/users/me/pictures/awesome-pic.png')

nodestream.upload(profilePic, {
  // directory and name are supported by all storage adapters, but each
  // adapter might have additional options you can use
  directory: 'avatars',
  name: 'user-123.png'
})
.then(results => {
  // results can contain several properties, but the most interesting
  // and always-present is `location` - you should definitely save this
  // somewhere, you will need it to retrieve this file later!
  console.log(results.location)
})
.catch(err => {
  // U-oh, something blew up 😱
})

Congratulations, you just uploaded your first file!

Downloading

Downloading a file is quite straight-forward - all you need is the file's location as returned by the upload() method and a destination stream to which you want to send the data. This can be any valid writable stream. Again, Nodestream does not care where you are sending the bytes, be it local filesystem, an http response or even a different Nodestream instance (ie. S3 to GridFS transfer).

// Let's create a destination for the download
const fs = require('fs')
const destination = fs.createWriteStream('/users/me/downloads/picture.png')

// We are hardcoding the location here, but you will probably want to
// retrieve the file's location from a database
nodestream.download('avatars/user-123.png', destination)
.then(() => {
  // All good, destination received all the data!
})
.catch(err => {
  // Oh well...
})

Removing

Just pass the file's location to the .remove() method.

nodestream.remove('avatars/user-123.png')
.then(location => {
  // The file at this location has just been removed!
})
.catch(err => {
  // Oh no!
})

Transforms

Nodestream supports a feature called transforms. In principle, a transform is just a function that acts somehow on (ie. modifies) the incoming or outgoing bytes, transparently, for each stream passing through Nodestream. Some use cases:

Calculating checksums
Compressing/decompressing data
Modifying the data completely, ie. appending headers/footers and whatnot

Registering a transform

WARNING!

The order in which transforms are registered matters! Transforms are applied to the stream in the order they were registered. For example, if you first register a checksum calculation transform and then a compress transform, the checksum will be calculated from the uncompressed data. Switching the order would cause the checksum to be calculated from the compressed data. There are use cases for both situations, so the choice of ordering is completely up to you.

When you configure your Nodestream instance, you should register transforms using the .addTransform() function.

// The first argument defines when the transform should be applied ('upload', 'download')
// The second argument is the transform's name - Nodestream will attempt to require
// `nodestream-transform-compress` under the hood, so make sure you have it installed!
// The third argument is an option configuration object which will be passed as-is to
// the transform stream when the time comes to use the transform.
nodestream.addTransform('upload', 'compress', { mode: 'compress' })
nodestream.addTransform('download', 'compress', { mode: 'decompress' })

Now, every time you call .upload() or .download(), the respective transform will be applied on the stream.

A transform can optionally publish some data about the applied transformations onto the results object.

There is no limit to the amount of transforms which can be registered per Nodestream instance, although there are some practical limitations which restrict you to only one particular transform type per Nodestream instance (ie. only one checksum transform with only one compress transform).

License

This software is licensed under the BSD-3-Clause License.

nodestream / nodestream.github.io Goto Github PK

nodestream.github.io's Introduction