til/ruby/add-progress-reporting-to-long-running-script.md

Add Progress Reporting To Long-Running Script

A script that is going to iterate over and process a ton of data can take a long time to run. It can be hard to predict how long it will take to run. So, it is nice to have some indication of it's progress as it goes.

Here is a small snippet that I add to the main loop so that I have some feedback while the script runs:

running_count = 0

tons_of_data.each do |item|
  running_count += 1
  if running_count % 1000 == 0
    print '@'
  elsif running_count % 100 == 0
    print '*'
  else
    print '.'
  end

  # process this `item` ...
end

Then I get some output that looks like this over time as the script runs.

...............................................................................
....................*..........................................................
.........................................*.....................................
..............................................................*................
...............................................................................
....*..........................................................................
.........................*.....................................................
..............................................*................................
...................................................................*...........
...............................................................................
.........*.....................................................................
..............................*................................................
...................................................@..................

I can get a sense of how quickly it is processing each record and roughly count how far along it is.