#Python – #FastAPI Webserver sharing information from values in a different thread

Hi !

After my yesterday post using Flask, I was sure that a FastAPI version will be needed, so here it goes:

I have a common scenario which involves:

• A sensor collecting information
• A web-server publishing the sensor information

Read my previous posts to understand why I think this is the simple way to solve this: Multi-threading.

• Thread 1, where an infinite loop request information from the sensor, and stores the latest value to be shared.
• Thread 2, where a web-server process requests and share the latest sensor information.

Easy ! And after a couple of tests, I manage to create a single file implementing this:

	# Bruno Capuano
	# simple webserver with fastapi
	# run with uvicorn 07:app -reload
	# test with http://127.0.0.1:8000/getdata
	# on each call, validate if the thread is started,
	# of the thread is None, start a different thread +1 a shared var
	from typing import Optional
	from fastapi import FastAPI
	import threading
	import time
	stateThread = None
	iCounter = 0
	app = FastAPI()
	def validateStateThread():
	global stateThread
	if (stateThread is None):
	print(f"start thread")
	stateThread = threading.Thread(target=mainSum)
	stateThread.daemon = True
	stateThread.start()
	@app.get("/getdata")
	def main():
	global iCounter
	validateStateThread()
	t = time.localtime()
	current_time = time.strftime("%H:%M:%S", t)
	return str(f"{current_time} – data {iCounter}")
	def mainSum():
	# increment counter every second
	global iCounter
	while True:
	iCounter = iCounter + 1
	t = time.localtime()
	current_time = time.strftime("%H:%M:%S", t)
	print(str(f"{current_time} – data {iCounter}"))
	time.sleep(1)

view raw WebServerMultiThreadRequestsFastAPI.py hosted with ❤ by GitHub

So at this point, you may think: why does El Bruno need this? So, let’s share an image that I’ll use in future posts:

Resources

• FastAPI, https://fastapi.tiangolo.com/
• Python – Multithreaded Programming
• Flask Webserver sharing information from values in a different thread