如何为烧瓶app.run（）设置启动时处理程序

Question

I haven't found a way to set a handler to detect when a flask server is already running. Consider the following code snippet:

import flask
import requests

def on_start():
    # send a request to the server, it's safe to do so
    # because we know it's already running
    r = requests.get("http://localhost:1234")
    print(r.text) # hello world

app = flask.Flask(__name__)
@app.route("/")
def hello():
    return "hello world"
app.run(port=1234, host="localhost", on_start=on_start)

The last line fails because on_start is not an argument of run , but hopefully you get the idea of what I'm trying to do. How can I do it?

Answer 1

What you can do is wrap the function that you want to kick off with before_first_request decorator as found here ==> http://flask.pocoo.org/docs/1.0/api/#flask.Flask.before_first_request

However, it won't get kicked off until someone makes a request to the server but you can do something like this:

import requests
import threading
import time
from flask import Flask
app = Flask(__name__)

@app.before_first_request
def activate_job():
    def run_job():
        while True:
            print("Run recurring task")
            time.sleep(3)

    thread = threading.Thread(target=run_job)
    thread.start()

@app.route("/")
def hello():
    return "Hello World!"


def start_runner():
    def start_loop():
        not_started = True
        while not_started:
            print('In start loop')
            try:
                r = requests.get('http://127.0.0.1:5000/')
                if r.status_code == 200:
                    print('Server started, quiting start_loop')
                    not_started = False
                print(r.status_code)
            except:
                print('Server not yet started')
            time.sleep(2)

    print('Started runner')
    thread = threading.Thread(target=start_loop)
    thread.start()

if __name__ == "__main__":
    start_runner()
    app.run()

Details & Source via Google-fu: https://networklore.com/start-task-with-flask/