Using delayed_job for a respond_to PDF call

Question

In a controller I have a respond_to block which creates a PDF with wicked_pdf like this:

respond_to do |format|
  format.html
  format.pdf do
    render pdf: "pdf",
      template:          'users/show.pdf.haml',
      print_media_type:  true,
      orientation:       'Portrait',
      page_size:         'A4',
      disposition:       'attachment'
  end
end

This works fine, but I want to use delayed_job to move this to a background job. I have setup delayed_job and it works fine. For instance, delivering a notification email is in the background now by adding delay:

Notifier.new(@user).delay.send_email

How can I do this for the PDF? I tried to move the render block to a separate method and call delay on it, but then it is not executed as a delayed job:

respond_to do |format|
  format.html
    format.pdf do
      render_pdf.delay
    end
  end
end

Answer 1

Rendering the response from the controller is instant and blocking I/O. You can not achieve this as you think. Instead you can move pdf generation to background job and give the user notice like 'PDF will be sent soon by email'. Once PDF generation done in delayed job you can just email the PDF from the delayed job.

respond_to do |format|
  format.html
  format.pdf do
    render_pdf.delay
    redirect_to some_path, 'PDF will be sent soon by email'
  end
end

Logic need to be added in delayed job to deliver PDF.