Calculates estimated time it takes for a block to return zero. Useful when running operations in parallel (e.g. migrations).

countdown.rb

# Calculates estimated time it takes for a block to return zero. Useful when
# running operations in parallel (e.g. migrations).
#
# Usage:
# Run in IRB/Rake/whatever: add_slugs_to_each_post # example of long-running operations
# Run in parallel IRB session: countdown { Post.where(slug: nil).count }
#
# sleep_time parameter is optional. The higher the value the more accurate the
# results, but the longer the method takes to run.

def countdown(sleep_time = 10)
  first_count = yield
  sleep sleep_time
  second_count = yield

  operations_per_second = (second_count - first_count) / sleep_time
  p "#{operations_per_second} operations per second"

  operations_remaining = second_count
  p "#{operations_remaining} operations remaining"

  seconds_remaining = operations_remaining / operations_per_second
  p "#{seconds_remaining / 60} minutes remaining"
end