Downstream

Downstream is a thin wrapper around hackney that turns the response body of an HTTP/S request into an Elixir stream.

It also provides a convenience wrapper Downstream.download/2 that will take care of streaming the data directly to a file at the provided output path.

Several more functions are available as well:

• download/3 allows you to provide a callback that will fire every chunk with metadata for the purposes of doing things like showing a progress indicator, but still handles streaming of the data directly to a file like download/2.

• stream/3 returns an Elixir stream of chunks containing iodata that can be piped directly into a File.stream! or other Collectable. If the metadata: true option is provided, then these chunks will instead be a Downstream.Chunk struct containing keys :data and :metadata which may be transformed for more advanced behavior.

Installation

def deps do
  [
    {:downstream, "~> 0.1.0"}
  ]
end

Implementation

Downstream operates by transforming the output of repeated calls to :hackney.stream_body/1 into an Elixir stream using Stream.resource/3, and packaging this with the the status code and headers returned by the initial call to :hackney.get/3, along with some useful metadata like total file length, length downloaded, and length remaining.