spotify/luigi — pull request #402 by paxan (2014-08-13 00:18:07+00:00)
Title: Add an event that tells how long run() took.

Quintessential example:

```py
@luigi.Task.event_handler(luigi.Event.PROCESSING_TIME)
def be_mindful_of_time(task, x):
my.metrics.send_value(type(task).__name__, x)
```