Storage in the cloud

We are going to use Amazon Web Services for storing the generated certificates and images.

Set up AWS account

You may choose to set up your own AWS account or you can get credentials from the coach. If you choose to set up your own account make sure to take all the necessary security precautions in order to avoid having your account compromised. It can be a very costly experience. [Instructions on how to set up AWS account with some screen shots?]

Create S3 bucket

[Instructions on how to create an S3 bucket with some screen shots?]

Configure and implement AWS upload

# Gemfile

gem 'aws-sdk'
gem 'dotenv'

Let's start with configuring dotenv

As early as possible in your application bootstrap process, load .env:

# lib/application.rb

require 'dotenv'
...
class WorkshopApp < Sinatra::Base
Dotenv.load
...

Create a .env and .env.example file in the project root:

touch .env
touch .env.example

Make sure to exclude the configuration file from version control by adding .env to your .gitignore:

# .gitignore

...
.env

Now, set up your credentials in your .env file:

# .env

S3_BUCKET=< your bucket name >
AWS_REGION=< your bucket region >
AWS_ACCESS_KEY_ID=< your access key id >
AWS_SECRET_ACCESS_KEY=< your secret access key >

Let's do some manual testing and upload a file to the S3 bucket

# in irb:

s3 = Aws::S3::Resource.new(region:ENV['AWS_REGION'])
obj = s3.bucket(ENV['S3_BUCKET']).object(file)
file = 'pdf/development/Thomas_Ochman-2015-11-23.pdf'
obj.upload_file(file, acl:'public-read')
obj.public_url

Let's add two properties to the Certificate class:

# spec/certificate_spec.rb

it { is_expected.to have_property :certificate_key }
it { is_expected.to have_property :image_key }

# lib/certificate.rb

...
property :certificate_key, Text
property :image_key, Text
...

We need to set these properties to Text rather then String due to the fact that length can exceed 50 characters.

We are going to do some major re-factoring of the CertificateGenerator, extracting some functionality to private methods and adding a method that will handle our upload to S3.

Update your certificate_generator.rb with the following code:

# lib/certificate_generator.rb

require 'prawn'
require 'rmagick'
require 'aws-sdk'
require 'dotenv'

module CertificateGenerator
  Dotenv.load!
  CURRENT_ENV = ENV['RACK_ENV'] || 'development'
  PATH = "pdf/#{CURRENT_ENV}/"
  TEMPLATE = File.absolute_path('./pdf/templates/certificate_tpl.jpg')
  URL = ENV['SERVER_URL'] || 'http://localhost:9292/verify/'
  S3 = Aws::S3::Resource.new(region: ENV['AWS_REGION'])

  def self.generate(certificate)
    details = {name: certificate.student.full_name,
               date: certificate.delivery.start_date.to_s,
               course_name: certificate.delivery.course.title,
               course_desc: certificate.delivery.course.description,
               verify_url: [URL, certificate.identifier].join('')}

    file_name = [details[:name], details[:date], details[:course_name]].join('_').downcase.gsub!(/\s/, '_')

    certificate_output = "#{PATH}#{file_name}.pdf"
    image_output = "#{PATH}#{file_name}.jpg"

    make_prawn_document(details, certificate_output)
    make_rmagic_image(certificate_output, image_output)

    upload_to_s3(certificate_output, image_output)

    { certificate_key: certificate_output, image_key: image_output }
  end

  private

  def self.make_prawn_document(details, output)
    File.delete(output) if File.exist?(output)
    Prawn::Document.generate(output,
                             page_size: 'A4',
                             background: TEMPLATE,
                             background_scale: 0.8231,
                             page_layout: :landscape,
                             left_margin: 30,
                             right_margin: 40,
                             top_margin: 7,
                             bottom_margin: 0,
                             skip_encoding: true) do |pdf|
      pdf.move_down 245
      pdf.font 'assets/fonts/Gotham-Bold.ttf'
      pdf.text details[:name], size: 44, color: '009900', align: :center
      pdf.move_down 20
      pdf.font 'assets/fonts/Gotham-Medium.ttf'
      pdf.text details[:course_name], indent_paragraphs: 150, size: 20
      pdf.text details[:course_desc], indent_paragraphs: 150, size: 20
      pdf.move_down 95
      pdf.text "Göteborg #{details[:date]}", indent_paragraphs: 120, size: 12
      pdf.move_down 65
      pdf.text "To verify this certificate, visit: #{details[:verify_url]}", indent_paragraphs: 100, size: 8
    end
  end

  def self.make_rmagic_image(certificate_output, output)
    im = Magick::Image.read(certificate_output)
    im[0].write(output)
  end

  def self.upload_to_s3(certificate_output, image_output)
    s3_certificate_object = S3.bucket(ENV['S3_BUCKET']).object(certificate_output)
    s3_certificate_object.upload_file(certificate_output, acl: 'public-read')
    s3_image_object = S3.bucket(ENV['S3_BUCKET']).object(image_output)
    s3_image_object.upload_file(image_output, acl: 'public-read')
  end

end

We also want our Certificate class to delete the associated images and pdf's from S3 when the record is deleted. For that, we need to create an before :destroy callback:

# lib/certificate.rb

...

before :save do
  student_name = self.student.full_name
  course_name = self.delivery.course.title
  generated_at = self.created_at.to_s
  identifier = Digest::SHA256.hexdigest("#{student_name} - #{course_name} - #{generated_at}")
  self.identifier = identifier
  self.save!
end

before :destroy do
  s3 = Aws::S3::Resource.new(region: ENV['AWS_REGION'])
  bucket = s3.bucket(ENV['S3_BUCKET'])

  certificate_key = bucket.object(self.certificate_key)
  image_key = bucket.object(self.image_key)

  certificate_key.delete
  image_key.delete
end
...

Make sure to run all your features and specs. The testing suite will take longer to execute then it used to.

We are actually hitting the AWS cloud storage in our tests (that is in principle a no, no!). There is much room for improvement of the way we set up our tests, but we will not focus on re-factoring our test at this point. The important take away for you is that testing play a vital supportive role in your development process and needs to be done in a smart way so it not becomes an obstacle.

Anyway, we have now implemented a cloud storage solution in our application. That is huge!