How to output the execution time of tasks in the luigi workflow system, as discussed [here](https://groups.google.com/d/msg/luigi-user/uivbf-luX9w/z0GCKKsIefoJ)

luigi_time_tasks_example.py

import luigi
import time

class TimeTaskMixin(object):
    '''
    A mixin that when added to a luigi task, will print out
    the tasks execution time to standard out, when the task is
    finished
    '''
    @luigi.Task.event_handler(luigi.Event.PROCESSING_TIME)
    def print_execution_time(self, processing_time):
        print('### PROCESSING TIME ###: ' + str(processing_time))


class TaskA(luigi.ExternalTask, TimeTaskMixin):
    '''
    A simple task representing a simple file with a few rows
    of dummy content
    '''
    def output(self):
        return luigi.LocalTarget('input.txt')
    

class TaskB(luigi.Task, TimeTaskMixin):
    '''
    A simple task that just outputs the content of its dependency
    into a new file with the the same name plus the extension .taskb
    '''
    def requires(self):
        return TaskA()

    def output(self):
        return luigi.LocalTarget(self.input().path + '.taskb')

    def run(self):
        time.sleep(1)
        with self.input().open() as infile, self.output().open('w') as outfile:
            for row in infile:
                outfile.write(row)


class TaskC(luigi.Task, TimeTaskMixin):
    '''
    A simple task that just outputs the content of its dependency
    into a new file with the the same name plus the extension .taskc
    '''
    def requires(self):
        return TaskB()

    def output(self):
        return luigi.LocalTarget(self.input().path + '.taskc')

    def run(self):
        time.sleep(2)
        with self.input().open() as infile, self.output().open('w') as outfile:
            for row in infile:
                outfile.write(row)


# If this file is executed as a script, run the last class in the dependency
# graph, TaskC.
if __name__ == '__main__':
    luigi.run(main_task_cls=TaskC)

If I'm not mistaken, the @luigi.Task.event_handler(luigi.Event.PROCESSING_TIME) will actually add the processing time callback to all luigi tasks, not just the ones that inherit the mixin. That is if the processing time event doesn't have some magic that other events don't have... The event_handler registrator adds it globally to all tasks on or below in class hierarchy from the one you call it on, so in this case that would be all luigi Tasks since it's called on Task.

awesome code snippets! 👍

Still useful years later! 😄

This is great! Any ideas how to get this into the UI?

It's excellent snippets! Thanks.