Python App with Watchdog Observer in Docker Container Throws FileNotFoundError

Question

I developed a tiny python app to constantly run -> utilizing the watchdog package's capabilities of checking for events. When I drop an event in one folder on my desktop, I want to subsequently upload that file to a google drive folder.

I'm hosting this script in a docker container. Everything runs and works as expected when I run the script locally, but when I execute docker run after building my image, I receive a FileNotFoundError: [Errno 2] No such file or directory thrown from the observer.start() method.

I've altered my Dockerfile to use a linux base image since inotify runs on linux, among adding in logic to handle a race condition before the volume is mounted, but alas, no cigar. Looking for any help here.

Here's my main.py script

import os
import json
import time
from datetime import datetime, timedelta
from googleapiclient.discovery import build, MediaFileUpload
from google.oauth2 import service_account
import mimetypes
import subprocess
from watchdog.observers import Observer
from watchdog.events import FileSystemEventHandler
import logging

# configure logger

logging.basicConfig(filename='heartbeat.log', level=logging.INFO, format='%(asctime)s - %(message)s')

# get current datetime
current_datetime = datetime.now()
date_string = current_datetime.strftime("%Y-%m-%d %H:%M:%S")

# scope
scopes = ['https://www.googleapis.com/auth/drive']

#paths
source_path = '/Users/nickrinaldi/Desktop/Dubstep-Test/staging'
destination_path = '/Users/nickrinaldi/Desktop/Dubstep-Test/uploaded'
mount_path = 'app/staging'
credentials_path = 'service_account_key.json'

# build event handler
class MyHandler(FileSystemEventHandler):

    def on_created(self, event):
        if not event.is_directory:  # Ignore directory creation events
            print(f"New file created: {event.src_path}")
            upload_and_move(event.src_path, destination_path=destination_path)

# build heartbeat 
def log_heartbeat():
    
    while True:
        print(f"Heartbeat: Script is still running at: {date_string}")
        logging.info(f"Heartbeat: Script is still running at: {date_string}")
        time.sleep(3 * 36000)

# build drive service

def build_drive_service(credentials_path, scopes):

    creds = None

    try:
        creds = service_account.Credentials.from_service_account_file(credentials_path, scopes=scopes)
    except Exception as e:
        print(f"Error intializing service account creds. Exception: {e}")
        logging.error(f"Error intializing service account creds. Exception: {e}")

    drive_service = build('drive', 'v3', credentials=creds)
    return drive_service

def parse_folder(source_path):

    items = []

    if os.path.exists(source_path):
        # for item in os.listdir(source_path):
        # item_path = os.path.join(source_path, item)
        items.append(source_path)
    else:
        print(f"The folder '{source_path}' does not exist")
        logging.error(f"The folder '{source_path}' does not exist")

    return items

# upload folder function
def upload_to_folder(raw_path, file_name, folder_id, drive_service):

    file_metadata = {
        'raw_path':  raw_path,
        'name': file_name,
        'parents': [folder_id]
    }

    mime_type, _ = mimetypes.guess_type(file_metadata['raw_path'])
    media = MediaFileUpload(file_metadata['raw_path'], mimetype=mime_type, resumable=True)
    request = drive_service.files().create(
        body=file_metadata,
        media_body = media,
        fields='id'
    )

    response = None

    while response is None:
        status, response = request.next_chunk()
        print(status, response)
        if status:
            print(f'Uploaded {int(status.progress())}%')

    print(f"Uploaded file {file_metadata['name']} complete")
    logging.info(f"Uploaded file {file_metadata['name']} complete")
    
def remove_path(source_path):

    substring = "Dubstep-Test/staging/"
    index = source_path.find(substring)
    path_new_name = {}

    if index != -1:

    # Remove everything before "Dubstep-Test/" including "Dubstep-Test/"
        new_file_name = source_path[index + len(substring):]
        path_new_name['raw_path'] = source_path
        path_new_name['file_name'] = new_file_name

        return path_new_name
    
def move_file(source_path, destination_path):

    try:
        # Copy the file to the destination path
        with open(source_path, 'rb') as source_file:
            with open(destination_path, 'wb') as destination_file:
                destination_file.write(source_file.read())

        # Remove the file from the source path
        os.remove(source_path)

        print(f"File moved from '{source_path}' to '{destination_path}' successfully.")
    except Exception as e:
        print(f"Error moving the file: {str(e)}")


def upload_and_move(source_path, destination_path):

    with open('secrets.json') as secrets_file:
        secrets = json.load(secrets_file)

    # folder id
    folder_id = secrets['folder_id']

    # build the drive service
    drive_service = build_drive_service(credentials_path, scopes=scopes)

    items = parse_folder(source_path)

    for item in items:
        item_dict = remove_path(item)
        upload_to_folder(item_dict['raw_path'], item_dict['file_name'], folder_id, drive_service)
        destination_path = destination_path + "/" + item_dict['file_name']
        move_file(item_dict['raw_path'], destination_path=destination_path)

# execution
if __name__ == "__main__":

    mount_path = 'app/staging'

    event_handler = MyHandler()
    observer = Observer()
    observer.schedule(event_handler, path=mount_path, recursive=False)
    observer.start()
    log_heartbeat()

    try:
        while True:
            time.sleep(5)
    except KeyboardInterrupt:
        observer.stop()
    observer.join()

And here's my Dockerfile:

# Use an official Python runtime as a parent image
FROM alpine:latest

# Set the working directory in the container
WORKDIR /app

# Install necessary packages (including pip)
RUN apk --no-cache add python3 py3-pip

# Copy the requirements file into the container at /app
COPY requirements.txt .

# Install any needed packages specified in requirements.txt
RUN pip install -r requirements.txt

# Copy the rest of the application code into the container
COPY . .

# Run your Python script
CMD ["python3", "main.py"]

And here are my build + run commands:

docker build -t google_drive_uploader .

docker run -v /Users/nickrinaldi/Desktop/Dubstep-Test/staging:/app/staging -d google_drive_uploader