Caching “streamed” content in Rails

In a previous article, I illustrated one way of generating streaming content programatically.

The application utilizing it is still slow in sending it, though, because it’s got to interact with the database, process the data, and so on. The ideal solution would be to cache it, however, the normal rails cacheing solutions don’t work, because the return value is a Proc, and if you try and write that to disk, it just writes the equivalent of proc_object.inspect, which doesn’t do me much good.

However, I figured out a clever way of running the exact same controller method “standalone”, and stashing the results to disk. I placed this file in scripts/cacher:

#!/usr/bin/env ruby

ENV['RAILS_ENV'] = ARGV.first || ENV['RAILS_ENV'] || 'development'

require File.dirname(__FILE__) + '/../config/boot'
require "#{RAILS_ROOT}/config/environment"
require 'console_app'

app.get '/mycontroller/big_results_method'

resp = app.controller.response
File.open("#{RAILS_ROOT}/public/cached_big_results.csv", 'w') do |out|
  resp.body.call resp, out
end

I think it could be improved, because it seems to be running the DB query twice – once during the actual app.get, and once again when the Proc is called. But, in any case, it works, and now I can call it from a cron job.

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