Question

I’m thinking about whether to host uploaded media files (video and audio) on S3 instead of locally. I need to check user’s permissions on each download.

So there would be an action like get_file, which first checks the user’s permissions and then gets the file from S3 and sends it using send_file to the user.

def get_file
  if @user.can_download(params[:file_id])
    # first, download the file from S3 and then send it to the user using send_file
  end
end

But in this case, the server (unnecessarily) downloads the file first from S3 and then sends it to the user. I thought the use case for S3 was to bypass the Rails/HTTP server stack for reduced load.

Am I thinking this wrong?

PS. I’m using CarrierWave for file uploads. Not sure if that’s relevant.

Answer 1

Amazon S3 provides something called RESTful authenticated reads, which are basically timeoutable URLs to otherwise protected content.

CarrierWave provides support for this. Simply declare S3 access policy to authenticated read:

  config.s3_access_policy = :authenticated_read

and then model.file.url will automatically generate the RESTful URL.