Daemons

A daemon is a process that runs forever. Like scheduled tasks, daemons often play a supporting role in web app backends - for example, by performing some background task such as processing data polled from a website or a queue.

Example

Here, the daemon continuously scrapes a stock price from a website, saving it to a multinode dict. When the service receives a GET request, the latest stock price is loaded from the dict and returned.

import time
import os
import requests
from fastapi import FastAPI
import uvicorn
import multinode as mn

app = FastAPI()

prices_dict = mn.get_dict(name="prices")

@mn.daemon()
def maintain_up_to_date_stock_price():
    while True:
        response = requests.get("https://stocksite.com/tickers/ABC")
        current_price = extract_price_from_html(response)
        prices_dict["ABC"] = current_price

        time.sleep(1)

@app.get("/price")
def get_price():
    price = prices_dict["ABC"]
    return {"price": price}

@mn.service(port=80)
def api():
    uvicorn.run(app, host="0.0.0.0", port=80)