将回形针pdf从S3转换为base64（Rails）

Question

I'm sending a base64 of a PDF to an external API endpoint in a Rails app.

This occurs regularly with different PDFs for different users. I'm currently using the Paperclip gem.

The problem is getting the PDF into a format that I can then convert to base64.

Below works if I start with a PDF locally and .read it, but not when it comes from S3.

Code:

def self.get_pdf(upload_id)

  # get URL for file in S3 (for directly accessing the PDF in browser)
  # `.generic` implemented via `has_attached_file :generic` in model
  # `.expiring_url` is paperclip syntax for generating a URL
  s3_url = Upload
      .find(upload_id)
      .generic
      .expiring_url(100)

  # open file from URL
  file = open(s3_url)

  # read file
  pdf = File.read(file)

  # convert to base64
  base64 = Base64.encode64(File.open(pdf, "rb").read)
end

Error:

OpenURI::HTTPError (404 Not Found):

Ideally this can just occur in memory instead of actually download the file.

Streaming-in a base64 from S3 while streaming out the API request would be awesome but I don't think thats an option here.

UPDATE:

• signed URLs from Cyberduck + Michael's answer will work
• paperclip URLs fail + Michael's answer results in below error

Error:

The specified key does not exist.

Unfortunately I need to use Paperclip so I can generate links and download PDFs on the fly, based on the uploads table records in my db.

Is there is a technicality about paperclip links I don't understand?

Answer 1

base64 =  Base64.encode64( get_me(s3_url).body ).gsub("\n", '')

def get_me(url)
    uri = URI(url)
    req = Net::HTTP::Get.new(uri)
    req['Any_header_you_might_need'] = 'idem'
    res = Net::HTTP.start(uri.host, uri.port, use_ssl: uri.scheme == 'https') do |http|
      http.request(req)
    end
    return res
  end