Recommended Elixir client for Backblaze B2

For file upload, I would definitely use ex_aws_s3, I have used it in the past with backblaze successfully on a project, you really don’t want to deal with things like large file uploads on your own and the s3 library works very well.

As for other backblaze specific endpoints, what I personally did was to just use a customized HTTPoison client and implement authentication and the few APIs I needed from their official documentation, it is very fast and easy to do as their API documentation is pretty good.

Also recommend rolling your own for the parts that are simple if you are concern about outdated libraries. Check out this article on Small Development Kits (SDK) from Dashbit if you need inspiration. SDKs with Req: Stripe - Dashbit Blog

Thanks for the mention. I tried Req/ReqS3 with a few S3-compatible services but not yet B2. If anyone runs into any problems please open up an issue!

Thank you for the recommendations! It’s comforting to hear that you’ve successfully used Backblaze B2 with the ex_aws_s3 client. I may give the recommendation from @ragamuf and @wojtekmach below a shot as well since the functionality I currently need is only limited to get_object and put_object. However if that doesn’t pan out, ex_aws_s3 will be my first choice. Thanks!

Thanks for the recommendation! I actually saw this article but didn’t realize part II had been published specifically about S3-compatible services. I will definitely give this a shot since my current requirements are only limited to put_object and get_object.

I am planning on following your recommendations in the article specifically for Backblaze B2 - will definitely let you know how it goes. Thanks for writing the article series!

Oh, there is one consideration for Backblaze in particular. If you’d upload huge files, instead of doing it in a single put_object (an HTTP PUT) you may consider doing multipart uploads, ExAws.S3.initiate_multipart_upload/2 and friends. These are not available in Req/ReqS3 and there are no plans at the moment.

@ragamuf and @wojtekmach I ended up implementing a small and lightweight B2 client using the advice in the article. This is only for my own use, so there is room for improvement (feel free to add any suggestions/feedback!) but here is what the end result looks like:

# in Livebook (or your `mix.exs`)
Mix.install([
  {:req, "~> 0.5.6"},
  {:typed_struct, "~> 0.3.0"}
])

defmodule B2.Client do
  use TypedStruct

  typedstruct do
    field :app_key_id, String.t(), enforce: true
    field :app_key, String.t(), enforce: true
    field :endpoint_url, String.t(), enforce: true
    field :bucket, String.t(), enforce: true
  end
end

defmodule B2 do
  defp new(%B2.Client{} = client, options) when is_list(options) do
    Req.new(
      # https://hexdocs.pm/req/Req.Steps.html#put_aws_sigv4/1
      aws_sigv4: [
        service: :s3,
        access_key_id: client.app_key_id,
        secret_access_key: client.app_key
      ],
      base_url: "#{client.endpoint_url}/#{client.bucket}"
      # retry: :transient
    )
    |> Req.merge(options)
  end

  def client(app_key_id, app_key, endpoint_url, bucket) do
    %B2.Client{
      app_key_id: app_key_id,
      app_key: app_key,
      endpoint_url: endpoint_url,
      bucket: bucket
    }
  end

  def get_object(%B2.Client{} = client, key, options \\ []) when is_binary(key) do
    req = new(client, options)
      
    case Req.get(req, url: key) do
      {:ok, %{status: 200, body: body}} -> body
      {:ok, %{status: 404}} -> nil
      error -> error
    end
  end

  def put_object(%B2.Client{} = client, key, object, options \\ [])
    when is_binary(key) and is_binary(object) do
    req =
      new(client, options)
      # TODO: properly set the content MIME type
      # https://developer.mozilla.org/en-US/docs/Web/HTTP/Basics_of_HTTP/MIME_types/Common_types
      # |> Req.Request.put_header("Content-Type", "text/csv")
    
    case Req.put(req, url: key, body: object) do
      {:ok, %{status: 200}} -> :ok
      {:ok, %{status: n} = resp} when n > 300 -> {:error, resp}
      error -> error
    end
  end
end

And here is some example usage:

# configure the client using the Application environment or environment variables etc

# in this example I am using LiveBook secrets
b2_app_key_id = System.get_env("LB_B2_APP_KEY_ID")
b2_app_key = System.get_env("LB_B2_APP_KEY")

# make sure to replace your <region>
endpoint_url = "https://s3.<region>.backblazeb2.com"
# make sure to replace your <bucket>
bucket = "<bucket>"

client = B2.client(b2_app_key_id, b2_app_key, endpoint_url, bucket)

# write a file
contents = """
col_1,col_2,col_3
A1,B1,C1
A2,B2,C2
A3,B3,C3
A4,B4,C3
"""
:ok = client |> B2.put_object("example.csv", contents)

# read a file
object = client |> B2.get_object("example.csv")

Thanks again to everyone that provided recommendations, I really appreciate the feedback