Coding The Stuffer

Like many teams before us (mysocial.io), we got to the point where we want our users to be able to upload files (mostly photos and videos) to our community.

Of course, there are tons of solutions out there. Starting from a simple S3 Bucket, to end up into some rudimental image storage service that we developed by another company I work with.

Anyway, it is more fun to face the challenge and build from scratch, right? Plus I thought it would be a good opportunity to learn more about streams and efficient memory management.

On top of it, I had some personal requirements for a File Storage service!

A File Storage service should…

work on my dev machine, offline, with as little memory footprint as possible
scale to a cluster in the cloud, with endless storage
work as the origin for a CDN like CloudFront
handle local cache, with configurable limits
handle file transformations like resize or gzip (also cached)
handle fine-grained access permission rules
allow adding custom features as simple Javascript plugins
work as Docker container
be NodeJS

Somehow I didn’t manage to find a product that matched all those requirements… So I made it :-)

Meet “the Stuffer”

I called it “Stuffer” because you put stuff in it, it handles that stuff, you fetch some stuff from it. That’s it.

NOTE: In order to enjoy the rest of this article you need Docker and some understanding of bash commands like CURL, or Postman.

The “Hello World” of file storage

The first thing that we want to try out is to simply run Stuffer on your local machine and be able to upload a file, and then download it. Let’s start a Stuffer instance:

docker run --rm -p 8080:8080 marcopeg/stuffer

Now let’s assume you have a file you want to upload, say an image, located at:

/Users/john/doe.jpg

We can issue a CURL command to upload that file to our newly created instance:

curl -X POST http://localhost:8080/upload \
    -F f1=@/Users/john/doe.jpg

Stuffer answers with a JSON document that contains some details about the upload:

{
  "files": [
    {
      "field": "f1",
      "fileName": "doe.jpg",
      "checksum": "d7fa2ae42c7e18ff5cfc405700641576",
      "type": "image/jpeg",
      "encoding": "7bit",
      "size": "55.8 kB",
      "bytes": 55767,
      "url": {
          "resource": "http://localhost:8080/public/de9d99a0-c8e5-4ca3-b732-45d358d3dedf",
          "original": "http://localhost:8080/public/de9d99a0-c8e5-4ca3-b732-45d358d3dedf/doe.jpg"
      },
      "meta": {}
    }
  ],
  "errors": []
}

The most interesting information is files[].url.original which gives us a direct link to the recently uploaded resource:

http://localhost:8080/public/de9d99a0-c8e5-4ca3-b732-45d358d3dedf/doe.jpg

If you copy that into your browser, you should see the original file.

NOTE: You can set an env variable DOWNLOAD_BASE_URL=mycnd.cloudfront.net that alters the resulting URL. This is useful when your run Stuffer under a CDN or on a custom domain.

Namespaces and Resource ID

We can break down the generated resource URL:

http://localhost:8080/public/de9d99a0-c8e5-4ca3-b732-45d358d3dedf/doe.jpg

into this template:

{downloadBaseUrl}/{space}/{uuid}/{fileName}

downloadBaseUrl > http://localhost:8080
space           > public
uuid            > de9d99a0-c8e5-4ca3-b732-45d358d3dedf
fileName        > doe.jpg

You can think to space/uuid as the account/repository in GitHub. A space is a container for multiple resources, each resource is identified by a unique universal id (or you can provide your own), and the resource can contain a file and its modifications.

The general idea is that you could upload a video, and have it automatically transcoded in different formats, or chunked for better streaming. Or anything else.

Anonymous Uploads, or Authentication?

We just performed an anonymous upload, meaning that we didn’t provide any credentials to the Stuffer instance. Just a file to store.

Under this circumstance, Stuffer creates the resource into the public space. It’s somehow similar to Dropbox’s Public folder. And if you’d like to change the name to match your needs, just provide an env variable UPLOAD_PUBLIC_SPACE=foo.

Of course, if you make your instance accessible from the Internet, you probably want to limit and regulate access to it. You can set the environment variable AUTH_ENABLE_ANONYMOUS_UPLOAD=false to deny anonymous upload access.

At this point, you will need to authenticate your upload request… With a JWT token!

Conclusions

It’s been a lot of fun to write this app. It took more or less a week to get to a first stable release, and now we are using it in production quite happily.

The main use-case that we focused on was the create new post feature of a classic social media app. In this case, a user chooses a file or takes a new picture for the post.

In this specific case, the space/UUID makes a lot of sense because each upload will be unique (hence the UUID) and associated with the user’s credentials. So the space name could be something like user-{userId}.

This structure has the advantage to scope all the files that got uploaded by a specific user under a single folder. In case the user drops out and enforces her GDPR rights to delete all her produced contents, it’s going to be a quick job.

I am aware of a different use-case, let’s call it the WordPress use-case, where a single entity (WordPress or a CMS) needs to upload resources to a custom and mutable folder structure. Stuffer doesn’t cover this use-case yet, but it shouldn’t be a problem to write an extension for it!

What do I read next?

Stay tuned because I’m going to write more Stuffer’s tutorials:

Upload with Authentication
Upload configuration and custom file limits
Apply modifiers to your downloads: how to get a black and white image?
Set up the store-s3 extension and run a full AWS S3 data mirror with configurable local cache

Other details are available here: