rich progress and multiprocessing

24 Mar 2022

How to use rich with python’s multiprocessing:

  • What is this?
    • Track progress of long running tasks when using multiprocessing
  • Why would you want to do this?
    • When you are doing lots of things with multiprocessing and each task can take a long time - feedback makes it easier to see that things are actually happening

What it looks like:

How to do it:

import multiprocessing
import random
from concurrent.futures import ProcessPoolExecutor
from time import sleep

from rich import progress

def long_running_fn(progress, task_id):
    len_of_task = random.randint(3, 20)  # take some random length of time
    for n in range(0, len_of_task):
        sleep(1)  # sleep for a bit to simulate work
        progress[task_id] = {"progress": n + 1, "total": len_of_task}

if __name__ == "__main__":
    n_workers = 8  # set this to the number of cores you have on your machine

    with progress.Progress(
        refresh_per_second=1,  # bit slower updates
    ) as progress:
        futures = []  # keep track of the jobs
        with multiprocessing.Manager() as manager:
            # this is the key - we share some state between our 
            # main process and our worker functions
            _progress = manager.dict()
            overall_progress_task = progress.add_task("[green]All jobs progress:")

            with ProcessPoolExecutor(max_workers=n_workers) as executor:
                for n in range(0, 20):  # iterate over the jobs we need to run
                    # set visible false so we don't have a lot of bars all at once:
                    task_id = progress.add_task(f"task {n}", visible=False)
                    futures.append(executor.submit(long_running_fn, _progress, task_id))

                # monitor the progress:
                while (n_finished := sum([future.done() for future in futures])) < len(
                        overall_progress_task, completed=n_finished, total=len(futures)
                    for task_id, update_data in _progress.items():
                        latest = update_data["progress"]
                        total = update_data["total"]
                        # update the progress bar for this task:
                            visible=latest < total,

                # raise any errors:
                for future in futures: