pace

Command-line progress bar and progress metrics. Helps you measure the 'pace' of a long-running script.

Pace

A node.js module that outputs a progress bar and other metrics to the command-line. It was originally conceived to help measure the 'pace' of long running scripts. We've used it to optimize scripts that would have taken hours to complete down to minutes, without having to wait the hours before knowing that the script could use some optimization.

$ npm install pace

Running the following code:

var total = 50000,
    count = 0,
    pace = require('../')(total);
 
while (count++ < total) {
  pace.op();
 
  // Cause some work to be done.
  for (var i = 0; i < 1000000; i++) {
    count = count;
  }
}

Will cause output to your console similar to:

The module exports a factory function to generate instances of Pace objects. So require('pace')(<options>) creates an instance of Pace, passing options to the constructor.

Options can either be an object literal, or an integer. If its an integer then it is the same as passing options with only the total specified.

require('pace')(100);
 
// Same as
 
require('pace')({total: 100});

Supported Options:

  • total - The total number of operations that YOUR script will execute.
  • maxBurden - The maximum 'burden' that the progress bar should incur. See more about burden below.
  • showBurden - Mostly for debugging. Show the current burden / skipped steps with the other metrics.

Signal to pace that an operation was completed in your script by calling pace.op().

If you would rather track the progress in your own logic, you can call pace.op(<count>) where <count> is the current operation interation (for example step # 50 of a 100 step process).

If your script has a dynamic amount of work to do (for example, depending on the results of previous operation there may be more steps to complete), you can freely change the value of pace.total. Just set the value like: pace.total = 200.

Depending on how intensive your operations are, calculating, formatting, and printing the progress bar might be much more expensive than the work you are doing. It would be silly if printing a progress bar caused your job to take significantly longer than it would have otherwise. Pace tracks a stat called 'burden', which is basically a percentage of the overall execution time that is being spent inside the progress bar logic itself.

The default maxBurden is 0.5, which translates to 0.5% of the total execution time. If this low burden is causing you to see progress reported less often than you would prefer, you can raise it to something like 20 (20%) via the maxBurden option.

The test/ folder contains some simple test scripts you can run to see the progress bar in action.