Pattern for saving / doing background work from a Falcon App using a queue from the standard Python Library

background_queue_falcon.py

# Credit: @vytas7 (Vytautas Liuolia)

import queue
import signal
import threading
import time
import uuid

import falcon


class Worker:
    _QUIT = object()

    def __init__(self):
        self._thread = threading.Thread(target=self.run)
        self._queue = queue.Queue()

    def start(self):
        self._thread.start()

    def run(self):
        while True:
            try:
                dataset = self._queue.get(timeout=1.0)
                if dataset is self._QUIT:
                    print('QUIT received; exiting the worker.')
                    break

                print(f'Saving to the DB: {dataset}...')
                time.sleep(5)  # <== Time consuming operation
                print(f'Saved: {dataset}')
            except queue.Empty:
                continue

    def submit(self, dataset):
        self._queue.put(dataset)

    def stop(self):
        self._queue.put(self._QUIT)
        self._thread.join()


class Dataset:

    def __init__(self):
        self._id = uuid.uuid4()

    def marshal(self):
        return {
            'id': str(self._id),
            'message': 'Hello, World!',
        }

    def __repr__(self):
        return f'Dataset<{self._id}>'


class Store:

    def __init__(self, worker):
        self._worker = worker

    def on_post(self, req, resp):
        dataset = Dataset()
        resp.media = dataset.marshal()

        self._worker.submit(dataset)


class App(falcon.API):

    def __init__(self):
        super().__init__()

        self._worker = Worker()
        self.add_route('/store', Store(self._worker))

        self._worker.start()

    def stop(self, signum, frame):
        print('SIGQUIT received, shutting down!')
        self._worker.stop()


app = App()
signal.signal(signal.SIGQUIT, app.stop)