Use Celery workers to copy a directory of files in parallel, with error tracking and a progress bar.

celery_copy_directory.py

#!/usr/bin/env python
import shutil
from pathlib import Path
from typing import Iterable, Tuple, Optional

import click
from celery import Celery
from celery.utils.log import get_task_logger
from tqdm import tqdm

app = Celery("copy", broker="pyamqp://guest@localhost//", backend="rpc://")

logger = get_task_logger(__name__)


@app.task(name="copy_files")
def copy_files(destination: str, filename: str) -> Tuple[str, int, Optional[str]]:
    def copy_without_overwrite():
        if destination_filename.exists():
            raise IOError(f"{destination_filename} exists")
        shutil.copy(filename, destination_filename)

    destination = Path(destination)
    filename = Path(filename)
    destination_filename = destination / filename.name
    error = None
    try:
        copy_without_overwrite()
    except Exception as e:
        error = str(e)
        logger.error(e)
    return str(destination_filename), filename.stat().st_size, error


@click.command("copy-directory")
@click.argument("source", type=click.Path(exists=True, file_okay=False))
@click.argument("destination", type=click.Path(file_okay=False))
@click.option("--chunk-size", default=50, show_default=True, help="Number of files to copy per worker")
def copy_directory(source: str, destination: str, chunk_size: int):
    """
    Copy a directory of files.

    This uses Celery workers to do the copy in parallel, displays a progress bar that updates according to file size,
    and tracks copy errors for individual files.

    This will not overwrite files. If the file already exists in the destination directory, an error will be logged.

    Too start the Celery worker run the following command in this directory.
    \b

         celery -A celery_copy_directory worker
    """

    def files() -> Iterable[Path]:
        return (filename for filename in source.iterdir() if filename.is_file())

    def total_size() -> int:
        return sum(filename.stat().st_size for filename in files())

    source, destination = Path(source).absolute(), Path(destination).absolute()
    Path(destination).mkdir(parents=True, exist_ok=True)
    result = copy_files.chunks([(str(destination), str(filename)) for filename in files()], chunk_size)()
    errors = []
    with tqdm(total=total_size()) as progress:
        def message_callback(message):
            if message["status"] == "SUCCESS":
                for filename, size, error in message["result"]:
                    if error is None:
                        progress.set_description(filename)
                        progress.update(size)
                    else:
                        errors.append(error)

        result.get(on_message=message_callback)

    if errors:
        print("The following files were not copied:")
        print("\n".join(errors))


if __name__ == "__main__":
    copy_directory()