Ruby SDK

Send email with Rack

Use Parcel Wing from a minimal Rack endpoint or any Rack-compatible Ruby application.

Install the SDK

The official Ruby SDK is published as parcelwing.

Terminal

gem install parcelwing

Rack endpoint

A Rack app returns a status, headers, and body. Keep the Parcel Wing client in server code and run it through rackup.

config.ru

# config.ru
require "json"
require "rack"
require "rack/request"
require "parcelwing"
 
parcelwing = ParcelWing::Client.new(api_key: ENV.fetch("PARCELWING_API_KEY"))
 
app = lambda do |env|
  request = Rack::Request.new(env)
 
  unless request.post? && request.path == "/send-welcome"
    return [404, { "content-type" => "application/json" }, [{ error: "Not found" }.to_json]]
  end
 
  payload = JSON.parse(request.body.read)
 
  emails = parcelwing.emails.send(
    from: ENV.fetch("PARCELWING_FROM_EMAIL"),
    to: payload.fetch("email"),
    template_alias: "welcome",
    template_params: { first_name: payload["first_name"] || "friend" }
  )
 
  [200, { "content-type" => "application/json" }, [{ id: emails.first.fetch("id") }.to_json]]
rescue ParcelWing::Error => error
  [error.status || 500, { "content-type" => "application/json" }, [{ error: error.code, request_id: error.request_id }.to_json]]
end
 
run app

Production notes

Keep PARCELWING_API_KEY in server-side environment variables.
Use saved templates for onboarding, invites, receipts, and account notifications.
Log request_id from ParcelWing::Error for support and debugging.