Stream CSV from Rails 3.2

Question

I am desperate to download streaming CSV downloads to my Rails 3.2.2 application.

I tried the gem csv_builder (https://github.com/dasil003/csv_builder), which advertises support for this function, however it seems that in Rails 3.2 there are some changes that do not allow work (it creates an "uninitialized persistent error ActionView :: Template :: Handler "at application startup).

Any other ideas or solutions? Thanks!

EDIT: To clarify, I need to export all the model records as a CSV file. There are so many lines that this is a timeout ... therefore the need for streaming. I have used Comma gem (https://github.com/crafterm/comma) for this in the past, but at the moment it does not support streaming.

Answer 1

OK, after a bit more research, I cracked the following in the controller. It will be a stream if response_body is given something enumerable (is that a word?). In addition, the server must be able to stream (I use Unicorn on Heroku). I would very much like that I did not have all this in the controller, so my next step is to somehow extract it.

  format.csv { @entries = Entry.all @columns = ["First Name", "Last Name"].to_csv @filename = "entries-#{Date.today.to_s(:db)}" self.response.headers["Content-Type"] ||= 'text/csv' self.response.headers["Content-Disposition"] = "attachment; filename=#{@filename}" self.response.headers["Content-Transfer-Encoding"] = "binary" self.response_body = Enumerator.new do |y| @entries.each_with_index do |entry, i| if i == 0 y << @columns end y << [entry.first_name, entry.last_name].to_csv end end } 

Answer 2

The approach I used with Rails 2.3.8 was to create a new thread to handle csv parsing, and then use an AJAX call to check the server to see if the file was ready (I relied on File.mtime )

Just pulled it out of the application to post it here, so I removed alot of csv parsing code and didn't include all the views

sorry the end of the day rush: D

Controllers / exports_controller.rb

  class ExportsController < ApplicationController require 'fastercsv' require 'generic_agent' require 'generic_record' def listing @this_filepath = "../html/whatever/" << Time.now.strftime("%I:%M:%S_%d:%m:%y") << ".csv" @spawn_id = spawn(:nice => 1) do FasterCSV.open(@this_filepath, "w") do |csv| csv << [ "outbreak_id"] end end render :update do |page| page.replace_html 'export_status', :partial => 'export_status_partial' end end def send_export @this_filepath = params[:with] csv_file = File.open(@this_filepath.to_s, 'r') csv_string = "" csv_file.each_line do |line| csv_string << line end send_data csv_string, :filename => "export.csv", :type => 'text/csv; charset=iso-8859-1; header=present', :disposition => "attachment; filename=export.csv" #send_file @this_filepath.to_s, :stream => false, :type=>"text/csv", :x_sendfile=>true #send_data csv_string, :filename => export.csv #File.delete(@this_filepath.to_s) end def export_checker filename_array = params['filename'].split(/\//) @file_found = 0 @file_ready = 0 @file_size = File.size(params['filename']) @this_filepath = params['filename'] if File.exists?(params['filename']) release_time = Time.now - 5.seconds if File.mtime(params['filename']).utc < release_time.utc @file_found = 1 @file_ready = 1 @file_access_time = File.mtime(params['filename']) @file_release_time = release_time @file_size = File.size(params['filename']) else @file_found = 1 @file_ready = 0 @file_size = File.size(params['filename']) end else @file_found = 0 @file_ready = 0 @file_size = File.size(params['filename']) end render :action => "export_checker" end end 

view / export / export_checker.rjs

 if @file_found == 1 && @file_ready == 1 && @file_size > 0 page.replace_html 'link_to_file', :partial => "export_ready" if @file_release_time page.replace_html 'notice', "<div>Completed #{@file_release_time.strftime("%I:%M:%S %A %d %B %Y")} :: file size #{@file_size.to_s}</div>" end page.visual_effect :highlight, 'link_to_file', :endcolor => '#D3EDAB' elsif @file_found == 1 page.replace_html 'link_to_file', "<div> File found, but still being constructed.</div><div>#{@this_filepath.to_s}</div>" page.visual_effect :highlight, 'link_to_file', :endcolor => '#FF9900' else page.replace_html 'link_to_file', "<div> File not found @file_found #{@file_found.to_s} @file_ready #{@file_ready.to_s}</div>" page.visual_effect :highlight, 'link_to_file', :endcolor => '#FF0000' end