rate_limited_update_checker.rb

# Put this in initializers/

# Kludge to avoid repeated globs & stats on closely spaced requests, eg. assets.
# Investigating at https://gist.github.com/cben/ca7a0d75734216816b39afdec5865224

# Patches https://github.com/rails/rails/blob/master/activesupport/lib/active_support/file_update_checker.rb
# http://apidock.com/rails/ActiveSupport/FileUpdateChecker

# TODO: make less noisy, accumulate stats, dump stats when actually found a change
# TODO: record times when assumed false, compare max mtime
# TODO: don't assume fresh if last check saw changes only after it's "quiet"?

require 'benchmark'

module RateLimitedUpdateChecker
  ASSUME_FRESH_SECONDS = 0.1

  def updated?
    thread_info = File.readlink('/proc/thread-self') rescue "#{Process.id} / #{Thread.current.object_id}"
    since_last_checked = Time.now - (@last_checked_at || Time.at(0))
    if since_last_checked.between?(0, ASSUME_FRESH_SECONDS)
      puts "[#{thread_info} #{to_s}] SKIPPING FILE UPDATE CHECK, STILL FRESH #{since_last_checked}sec."
      false
    else
      result = nil
      t = Benchmark.measure { result = super }
      puts "[#{thread_info} #{to_s}] Re-checking for updated files after #{since_last_checked}sec...   => #{result}, took #{t.to_s.strip}sec"
      @last_checked_at = Time.now
      result
    end
  end
end

ActiveSupport::FileUpdateChecker.prepend RateLimitedUpdateChecker