Using threading with flask

Using threading with flask. More common would be to start the thread whose target is, for example, def run_server(): asyncio. run()" which starts the Discord bot part) to launch the Flask server; It'll just run the flask, get stuck on that until I Ctrl+C out of the Flask server, then it'll proceed to start the Discord bot. app = Flask(__name__) @app. flask run --without-threads . Feb 26, 2015 · @BlackMamba : @methane 's answer explained the reason, using t = threading. Flask, as a WSGI application, uses one worker to handle one request/response cycle. import threading def function1(): # your code here def function2(): # your code here You start threads like this: threading. PyThreadState_SetAsyncExc(thread_id, ctypes. start() # will start the function and continue, even if the function still runs. run()" somewhere in my code (before calling "client. Oct 10, 2019 · Approach #2: Use eventlet. I have a flask endpoint that takes 40 seconds to run the code (CPU intensive work). Follow. We were running into issues where these threads would emit something and it would take forever for it to be pushed to clients, until we switched to async_mode='threading'. set the exit_event. As far as I can tell it doesn't appear that the Flask documentation has been updated as a result of the bug fix, so the best documentation can be found in the bug report Jun 7, 2020 · Inside flask function: Thread-1. flaskenv files. time. NumFound(path) return json. start() So, the answer is that it launches a new thread on each request. Yes, Flask URL routing supports the use of HTTP methods. The same problem persists if I were to for example add "app. b = 2 new_t = threading. Another use case is when the result is not Jul 18, 2023 · I am trying to use threading in flask to train a model in parallel. Perhaps someone else have a more elegant pythonic solution. To solve your issue, you should either disable debug ( app. Share. In this case it doesn't run in parallel. Make sure to not call your application flask. you need an application server that is compatible with WSGI that will handle creating a pool of workers (threads, processes, ) that will take care of concurrently answering the requests that came from the May 13, 2022 · from flask import Blueprint from threading import Thread bp = Blueprint('backend', __name__) def backend(app): thread = Thread(target=start, args=(app,)) thread. . You can also retrieve the state from a task through Flask if you want the client to verify that the task was/was not completed. set () inside the task function to end the task or prevent the task from running. Thread(target=function2). Jul 7, 2015 · Flask can run just fine in a separate thread, but the reloader expects to run in the main thread. May 10, 2016 · You can just process this in a Thread and forget about the result. Flask supports async coroutines for view functions by executing the coroutine on a separate thread instead of using an event loop on the main thread as an async-first (ASGI) framework would. Sep 7, 2018 · Celery and Flask are then two separate python processes communicating with one another. Just launch it like this instead. import time. So it’ll create one process and two threads. gunicorn). monkey_patch() And then change the SocketIO object creation line to: socketio = flask_socketio. class EndpointAction(object): def __init__(self, action): self. In this case all child threads will be joined automatically and the main thread will be successfully stopped immediately. This synchronous task is fine when a user needs the result of calculation immediately. In the single-threaded mode, a Flask application can handle no more than one HTTP request at a time. 1) if user_text May 22, 2021 · In order for the asyncio event loop to properly run in Flask 1. with flask, you are creating the web application part. start() Both will live at the same time Dec 13, 2019 · args = (request, client_address)) t. Feb 25, 2016 · 24. Jan 1, 2020 · While Testing the live video streaming (laptop and USB webcam) through flask, I am not able to display the video streaming on the main page as well as while accessing the decorator. start Aug 14, 2021 · How to add a background thread to a Flask app? Posted on August 14, 2021 · Last updated February 7, 2022 · 4 minute read. app. Thread (target = worker, name = "NewThread") new_t. It is used to create async functions in Python. 📌. Knowledge of Python and basic knowledge of Flask is required. Those can also be passed as arguments to app. This will call my backend() function from adding threaded=True inside app. I. The audit is not CPU intensive at all, it's just some db inserts and logging. Using flask's development server, I can use app. _threads = [] self. Improve this answer. results () needs to issue multiple http requests before returning, and I would like to do them in I have web application written in Flask. self. Above is the sample code of what I am trying to do. These are of size 8GB collectively. Note:-The code works with python3. Sorted by: 0. Jan 19, 2014 · I'm a little bit new with the concept of application schedulers, but what I found here for APScheduler v3. This is only or a prototype to be used and tried and it is not a final solution that will see production some day. 1, it's something a little bit different. The easiest way to run a Flask application is to use a built-in development server. x, the Flask application must be run using threads (default worker type for Gunicorn, uWSGI, and the Flask development server): Each thread will run an instance of the Flask application when a request is processed. Dec 28, 2023 · Create a simple Flask application and import Flask-SocketIO: from flask import Flask. Each request still ties up one worker, even for async views. This verifies that Flask is indeed running the view functions in a separate thread other than the main thread. There's a route defined as follows: def sentence_numfound(path): nf = util. Then everything worked perfectly, except we now get the warning: WebSocket transport not available. Timer is a good idea, as the request will return but I'm leaving the server with a resident thread waking up every 30 minutes. First we need to patch the Python threading system at the start of the program: import eventlet. Now you can run it without threads like so FLASK_APP=server. run() will enable threads per-request for multiple concurrent requests to the server. start() return '', 200. Aug 15, 2019 · After looking at the source code, I see that Flask has the --without-threads parameter, which was added as a result of this bug report. backend(app) to my create_app() function in __init__. run: app. Once you have it at this point you can switch to a production WSGI such as gunicorn. To run the application, use the flask command or python -m flask. But even this beast supports two modes of request handling. start() return 'hello'. By default, a route only answers to GET requests, but this can be changed by providing the methods argument to the route () decorator. I just need a way to create a queue so Nov 18, 2013 · In fact, even if you run Flask with multiple threads, Flask is smart enough to keep the request objects isolated. This is your application code for publishing ping results via websockets to your browser (same as we would see while running ping command in Linux . May 2, 2023 · Use SQLAlchemy's scoped_session: To work with SQLAlchemy in a multi-threaded environment, it's recommended to use a scoped session. For example say I want to use python multiprocessing for CPU intensive work (or multithreading for IO intensive work). What worked for me is to specify Agg as Matplotlib backend. 6, Flask 0. To trigger the webcam we pass ‘0’ as the argument. g. serve(hello, 'localhost', 8899) as ws_server: await asyncio. Jul 14, 2022 · The function thread. After we changed the app. _threads. 3. Concurrency of my web application can go upto 1000 requests. To use celery commands, Celery needs an app object, but that’s no longer directly available. I am new to python and read that python has GIL, which means at one time only one thread can run irrespective of number of cores. If you want to make a threaded function that runs in background, just use the threading module, like this: from threading import Thread. sleep (0. start() self. and modify the task function to better mimic a long or indefinite running task. I believe that for the newest versions, the package structure, class names, etc. env and . run to be threaded=True, this is how the responses look like now. The upside is that you can run async code within a view, for example to make multiple concurrent database queries, HTTP requests to an external Mar 22, 2017 · I am developing a web app which has a service/task which might take a long time to finish. use('Agg') import matplotlib. pythonapi. request = {thread_id1: Request1, thread_id2: Request2,} Flask uses werkzeug Local class; import threading import time class A: b = 1 my_obj = A def worker (): my_obj. In doing so, it becomes possible for two threads, each handling a different request, to simultaneously call request. sleep(5) return redirect("/goodbye") Is this possible? Why when this code is ran it does not work as intended? /hello should load, then after 5 seconds it should redirect, but it never redirects and I Mar 27, 2023 · The Waitress package is an essential tool for Flask developers who want a production-ready, efficient, and easy-to-use WSGI server. The Flask docs provide several examples on how to set that up. Basic request lifecycle with Flask goes like this: Flask gets a request. run(app, host='::', port=1234) app. Now every function of the socket namespace will act as an event if the function starts with on_ like in this example Mar 25, 2018 · daemon for a child thread means that the main thread won't wait till this daemon child thread is finished its job if you're trying to stop the main thread. 0 is not a valid address to navigate to, you’d use a specific IP address in your browser. Create a make_celery. e. This short article covers a template for setting up a Flask based web app with a background thread. py because this would conflict with Flask itself. But if I set threaded true to my application it is showing unknown behavior. I have been using flask, and some of my route handlers start computations that can take several minutes to complete. Its pure Python implementation, simple configuration, and efficient request handling make it a popular choice for serving Flask applications. 1 and Uwsgi. app = Flask("proxapp") import datetime. 0. from flask import (. With model_training() called in thread returns a status as its in a far loop and works fine as expected. If you have 2 processes with 4 threads each, that's 8 concurrent requests. io client from these threads. daemon = self. use_reloader=False ). append(t) t. daemon_threads. Flask comes with a built-in development web server, but you shouldn't be using it in production. Ultimately, I need to use the Dec 27, 2019 · Deploy Flask application using Flask dev server. This code snippet demonstrates the integration of Flask-SocketIO into your Flask application. Mar 1, 2022 · For example, the workers would be threads if you're using the Flask Development Server with its default configuration. response = Response(status=200, headers={}) def __call__(self, *args): Oct 26, 2023 · Now, enter the below code into “myapp. pyplot as plt # Your code here You can refer to Matplotlib documentation (Matplotlib in a web application server) for the details. May 15, 2020 · Once the jobs are completed, the awakened thread need a way to get inputs from the jobs. Thread(target=long_running_task) thread. When a request comes in to an async view, Flask will start an event loop in a thread, run the view function there, then return the result. Apr 19, 2018 · I was on the same situation, Flask with Matplotlib combo. from flask_socketio import SocketIO. This is necessary for Flask to remain backwards compatible with extensions and code built before async was introduced into Python. May 23, 2017 · Yes you can. run() doc, this is also briefly mentioned in the changelog part: Changed in version 1. . , have changed, so I'm putting here a fresh solution which I made recently, integrated with a basic Flask application: Jul 2, 2019 · Thank you, it looks like it has been asked about debug, I am wondering about threading. My main aim is to access multiple cameras through using flask mentioned below is the code I am working on . SocketIO(flask_app, always_connect=True, async_mode='eventlet') Now socketio uses Websocket. with threading you can't speed up a CPU-bound task, you must use multiprocessing. run (threaded=True) and my server will continue to respond to other requests while it's off performing these multi-minute computation. start() I then added backend. when the main thread executes this sleep call) time. This module lets you write concurrent code using async/await syntax. If you just want to know about success/fail for the task. dumps(nf. from flask import Flask, Response. For Jun 18, 2015 · threading=True with flask-socketio. Nov 29, 2021 · When flask. Let’s study client-server multithreading socket programming by code-. May 28, 2021 · I don't know what you mean by "overwritten" but both calls are required if the server is started this way. Flask will process one request per thread at the same time. Not sure whether that helps in your case, it sounds like maybe you're trying to receive one request from the user and then have the app use threading. from flask import jsonify. path and get the correct information for their respective requests. and finally returns the result. state)) than Flask says that he wants to get this variable from the app. In Flask application I am loading some Machine Learning models. asyncio. Using this technique, the ScopedSession provides a quick and relatively simple way of providing a single, global object in an application that is safe to be called upon from multiple threads. Apr 9, 2022 · If you need to wrap a Flask application inside your project, create a separate class to your needs and add functions that should be executed. daemon and self. We can either provide the path of the video file or use numbers to specify the use of local webcam. This is the difference between using threads on the server side. is parses input parameters. action = action. gunicorn server:app. $ flask --app hello run. The route in your Flask app. event () outside of the route function. if not t. thread = threading. You can store the state of the task in Database and query it when needed. More info is here. 45. id] = thread. If you need asynchronous support, Gunicorn provides workers using either gevent or eventlet. def bg_func(): doSomething. And if in need of passing parameter to the target function, use the arg=(parameters) keyword argument. run (debug=True, use_reloader=False). the request handling becomes sequential. This is my code. py: socketio = SocketIO(app, always_connect=True) But I noticed that my application could not answer several requests at the same time. Aug 15, 2019 · if the background thread has a lot of stuff to audit, it blocks the main thread, the more stuff in memory, the longer it blocks the main thread. So I thought of Gunicorn with Flask. I need to run in threading mode. run threaded=False, even if all the requests were issued simultaneously, the requests were processed one by one. 457s) at once. py or something similar. As suggested by everyone, I can't use Flask in production. Flask doesn't spawn or manage threads or processes. Hello, I am using flask-socketio to add socketio functionality in my flask api. 0. route('/') def index(): return 'hello'. 0: If installed, python-dotenv will be used to load environment variables from . py_object(SystemExit)) Share. Nov 27, 2018 · November 27, 2018. Therefore, the get_status_list method returns the status_list back to the caller. You just need to import the threading module. start_new_thread () is used to start a new thread and return its identifier. Jun 25, 2021 · This question is regarding using python multi-processing (or multi-threading) code inside a flask endpoint. I have looked at Twisted and Klein, but I'm not sure they are overkill, as maybe Threading would suffice. Flask-SQLAlchemy , an extension for Flask , provides a scoped_session that automatically creates a new session for each thread and keeps the session open for the duration of the thread. This flask function works as a webhook triggered by AWS lambda that creates a thread to process the data without making the lambda wait for it to finish. I'm using Python 2. t = Thread(target=bg_func) t. start () while True: user_text = input ("let's do some work on the main thread: ") # will only resolve the GET request after user input # (i. threads[data. py”. Putting it Together Oct 20, 2020 · Step3- Capture Video using OpenCV : Create a VideoCapture () object to trigger the camera and read the first image/frame of the video. That should satisfy your multithreaded approach. Save it as hello. The upside is that you can run async code within a view, for example to make multiple concurrent database queries, HTTP requests to an external May 16, 2019 · We also want to emit data to the socket. This is the only task which I need Flask to run asynchronously, and I would like some advice on how best to implement this. The first argument is the function to call and its second argument is a tuple containing the positional list of arguments. But, I would like to train a model by using model_train() (below code). You need to tell the Flask where your application is with the --app option. That's the responsability of the WSGI gateway (eg. py would look like: Apr 19, 2014 · I would like to use concurrency when responding to a specific route without creating extra threads on every request. Feb 1, 2022 · Flask using thread to run code after/alognside return. – Callers who call upon the registry in a different thread get a Session instance that is local to that other thread. The threading module helps us to create multiple threads in a python program. Apr 6, 2020 · To solve the issues of multi-threading in Flask we can use dictionary data structure, e. Example Python 3 Flask application that uses threading. May 19, 2021 · 1 Answer. _active. py flask run. Until now everything worked fine by initializing the application like this: main. py file that calls the Flask app factory and gets the Celery app from the returned Flask app. extensions["celery"] Point the celery command to this file. from flask import Flask. eventlet. Oct 14, 2021 · thread = Thread(target=process_audio, kwargs={'bucket_name': bucket_name, 'key': key, '_id': _id, 'extension': extension}) thread. If nothing else, it's an interesting exercise in tracing code paths. 10. And the RAM of machine is 15GB. Jun 8, 2012 · Add a comment. run(the_server()) and then we have the_server as a coroutine: async def the_server(): async with websockets. from example import create_app flask_app = create_app() celery_app = flask_app. To get cool features like separate processes for each request and static file serving, you need to run an actual web service and a WSGI service in front of your Flask application. Dec 6, 2021 · declare the threading. run() In the index route (/) we spawn a thread for each exporting task, and we return an ID to that task so that the client can retrieve it later with the progress route (/progress/ [exporting_thread]). app = Flask ( __name__) socketio = SocketIO ( app) # Rest of your Flask app code. Performance¶. debug = False ), or disable the reloader ( app. Within each thread, a separate asyncio event loop is created for Nov 8, 2019 · If I add new argument (def do_it(FirstArgument, SecondArgument, mydata. Thread(target=function1). py : socketio. start() threading. If you're interested in learning more about the differences between threads, multiprocessing, and async in Python, check out the Speeding Up Python with Concurrency, Parallelism, and asyncio article and the Concurrency in May 18, 2018 · from flask import Flask. py, right before the end of my function. This is not the same as Python’s async/await, or the ASGI Mar 3, 2022 · Here you can see you can use the base class that we created before BaseSocket. The items that need to be audited are added to an object in memory from the main thread and are passed by reference to the This is working but I don't know if threading. How can I pass this data to the do_it function? And one more question. import matplotlib matplotlib. Aug 7, 2015 · run and provide a callback to be executed when the method returns, whilst Flask can continue to process requests. Condition to wait for several Flask-APScheduler one-off jobs to complete execution 4. block_on_close: if self. Introduction. Feb 16, 2022 · I user the below code to kill threads when I am existing a server , My suggestion is to kill all active threadss before opening a new one. daemon = True thread. Future() # run forever. In the Flask. Thread(target=do_sth_else) seem to work for me. With threaded=True requests are each handled in a new thread. route. does necessary calculations. All the requests come back at 1 second (1. Async functions require an event loop to run. for id, thread in threading. thread = ThreadXXX(data) thread. results(path)) nf. Jun 5, 2019 · Here is a more succinct usage to demonstrate: import time from stuff_mock import StuffMock mocker = StuffMock (8099) mocker. Async with gevent or eventlet¶ The default sync worker is appropriate for many use cases. items(): ctypes. I also do know that I can run Flask in main thread, and I am NOT Using debugging. The exporting thread updates its progress value every time it thinks it is appropriate. Background jobs with Flask. _threads is None: self. py Jan 26, 2021 · For example, if there’s a program in which there are two async functions.