Using threading with flask. I made a test and opened 100 threads.
Using threading with flask And if in need of passing parameter to the target function, use the arg=(parameters) keyword argument. Upvoting indicates when questions and answers are useful. Feb 19, 2021 · Extremely good point. May 27, 2025 · Threading Example Implementation Utilize the threading module in Python. using static is a new kind of using clause that lets you import static members of types directly into sco Mar 8, 2017 · User kokos answered the wonderful Hidden Features of C# question by mentioning the using keyword. 54K subscribers 2 May 5, 2017 · I have python-socketio used in Flask and want to start Thread instance and emit signals from it when signal comes. So I thought of Gunicorn with Flask. from flask import Flask from threading import Thread app = Flask(__name__) def process_task(): # Perform long 1 day ago · Threads are particularly useful when tasks are I/O bound, such as file operations or making network requests, where much of the time is spent waiting for external resources. It merely ensures that the context is correctly propagated when threads are used. However, I can never get this to work. I. Of all the advantages using provides, it can't be combined with other predicates: select*from t join t2 using(i) and on 1 wouldnt work. run_simple - one of those arguments is threaded which defauls to True as of Flask 1. Feb 1, 2022 · I am trying to run code after I return my template in flask Here is sample code @app. Oct 21, 2010 · I had been using cocaine. Concept Create separate threads to handle long-running or blocking tasks. To make your Flask web and Telegram bot work simultaneously, you can use threading in Python. dumps (), so it's recommended to use jsonify () whenever possible in Flask apps. using static is a new kind of using clause that lets you import static members of types directly into sco Jul 10, 2019 · SQLAlchemy and Postgres are a very popular choice for python applications needing a database. start() # will start the function and continue, even if the function still runs doSomethingelseAtSameTime # runs with bg_func You can also have multiple background threads. That's the responsability of the WSGI gateway (eg. 3. Thread(target=app. Jun 17, 2015 · I have been using flask, and some of my route handlers start computations that can take several minutes to complete. I am using flask with pytorch ( with cuda ) , every thread is taking 20 to 30mb and never release it when using empty_cache and even after thread is executed successfully. In the single-threaded mode, a Flask application can handle no more than one HTTP request at a time. Meaning, with a reference point in the past, starting a time before then up to the reference point, I was habitually using cocaine up to and including that point. 17. See the examples in Contextual/Thread-local Sessions for setting up your own thread-safe sessions: Apr 24, 2024 · With Flask-SocketIO you have three concurrency options: threads (async_mode='threading', and the --threads option in Gunicorn) gevent eventlet Using threads is going to give you the biggest compatibility with third-party libraries libraries. In fact, trying "python --enable-threading" does not work. So for the latest versions of Flask, the default development server will be able to serve multiple clients simultaneously by default, and will handle that for When the flask app is called using gunicorn with worker type gevent, I understand for each incoming request, a greenlet is spawned. Process), everything works as expected, and I can spin up arbitrary numbers of mockers without blocking. Using multiprocessing instead of threatening is suggested workaround. In flask app I have: Jun 22, 2020 · The first, t1 = threading. 2, eventlet 0. serving. Similarly, if within using body something may happen, which is not directly related to the variable in using, then I wrap it with another try for that particular exception. Hence, in application. This makes sense for a quick file IO or database action, for example, that doesn't change the Flask response to the user. While using them in the context of a python WSGI web application, I’ve often encountered the same kinds of bugs, related to connection pooling, using the default configuration in SQLAlchemy. Jul 23, 2025 · The below code demonstrates the use of ThreadPoolExecutor, notice unlike with the threading module we do not have to explicitly call using a loop, keeping a track of thread using a list or wait for threads using join for synchronization, or releasing the resources after the threads are finished everything is taken under the hood by the constructor itself making the code compact and bug-free. Flask doesn't spawn or manage threads or processes. Not only does it squeeze out performance gains from the application by improving concurrency, it can potentially enhance user experience by reducing wait times. run (host=HOST, port=PORT, threaded=True) This code is controlled by Dataiku, and it is injected to webapp editor. Thread(target=do_sth_else) seem to work for me. Mar 4, 2021 · Trying to use threading. If I have 100 threads the 1st 100 calls will take 20 30mb each. from flask 2 days ago · Yet, Flask developers seamlessly use `from flask import request` to access request-specific data (like headers, form data, or URL parameters) in their view functions—*as if `request` were a global variable*. Using this class, you can create an instance of the Thread and then start it using the . Oct 22, 2008 · But if you put the using declaration inside a namespace it's limited to the scope of that namespace, so is generally OK (with the usual caveats on your particular needs and style). Below are few experiments with different configurations of Gunicorn. Now when t1. Camera streaming (Open-CV + Flask) and display on different threads with safe synchronization May 22, 2021 · This article looks at Flask 2. Timer to run Flask app periodically Asked 4 years, 2 months ago Modified 4 years, 2 months ago Viewed 328 times In this lesson you'll learn about the need to send emails asynchronously and how to do that in a Flask application. These are super quick, scalable, handle threading, and it is one of the Flask-recommended methods. async_handlers – If set to True, event handlers for a client are executed in separate threads. Oct 15, 2024 · Increase OpenCV speed with Python and Multithreading. , two routes updating app. start() return 'hello' def long_running_task(): time. I need to run in threading mode. How will the threads behave in this set up and are they monkey patched as greenlets? How does the thread switch tie in together with the use of gevent?. app_variable is the variable with the application. while running an app) see this excellent post: How to schedule a function to run every hour on Flask? Feb 7, 2016 · The server log says something about using the --enable-threading flag, but there are not suggestions on how this is done. But even this beast supports two modes of request handling. py file and the behavior can be instantly reproduced. However, I can't seem to pass the application context to the sub-process, and existing libraries are focused on requests - I need this process to start running in parallel when flask is run, no later. However, note that longer running tasks will benefit more from using something like Celery for real asynchronous processing. May 27, 2025 · Table of Contents Setting Up the Environment The Core Idea Key Components of the Code 1. Check the documentation for May 13, 2022 · I am trying to implement multiprocessing or threading in my flask __init__. run accepts additional keyword arguments (**options) that it forwards to werkzeug. I will have been using cocaine. run(**kwargs)), does not pass the function but calls the function in the main thread. I made a test and opened 100 threads. I am using multithreading in a Flask app and want each thread to append to an entry in a database. One route sends a simple message, and another route receives a number from the URL and returns its square. Feb 5, 2025 · FastAPI vs Flask: Key Differences and Use Cases Both FastAPI and Flask are Python web Tagged with fastapi, flask, python, programming. module_import is the dotted import name to the module with your application. GetResponse() inside of the root block of a method, then the using variable will have method scope, actually similar to the defer statement in go. It appears you have eventlet Dec 6, 2021 · I am wondering is there something special I need to do for ending a thread job in Flask? Here is the sample code: from flask import ( Flask, jsonify, render_template, request ) import threading Nov 17, 2025 · However, if you enable multi-threading (e. py to implement a sub-process that will handle some back-end work for me. , flask run --threaded) or use a production server with threads, concurrent writes to application-scope variables can cause race conditions (e. 3, Flask 0. Follow this step-by-step tutorial for faster video processing. 0's new async functionality and how to leverage it in your Flask projects. When your application uses Flask-SocketIO, a plain WSGI web server isn't sufficient, because WSGI does not support WebSocket, the WSGI protocol needs unofficial extensions to support this protocol. Oct 9, 2022 · In this post we will learn how to use waitress as a WSGI (Web Server Gateway Interface) for a flask application Why use waitress The default flask server is not meant for production deployment since it is single-threaded and not highly secure Waitress is meant to be a production-quality pure-Python WSGI server with very acceptable performance What is Waitress Waitress is a pure python WSGI Jun 22, 2021 · I'm writing a server for sending rendered images to clients (browsers) using Flask. Jul 18, 2014 · So if you are using using var resp = req. A simple test you can do is to run your application in the "threading" async_mode, which uses standard threads. In Flask application I am loading some Machine Learning m May 19, 2021 · If you want to make a threaded function that runs in background, just use the threading module, like this: from threading import Thread def bg_func(): doSomething t = Thread(target=bg_func) t. If your server can fork itself, like here Jan 12, 2016 · To make a WSGI application available online you need to expose it through a web server. 2 A typedef-name can also be introduced by an alias-declaration. To use the same json encoder and decoder as a Flask application, use flask. Thread(target=runApp) is used the function is passed and not called to the main thread. Contribute to sintezcs/flask-threads development by creating an account on GitHub. What I cannot do is implementing a queue, feed it with items from a list, and have thread workers work on it. When instrumented, new threads created using threading. It is important to note that this instrumentation does not produce any telemetry data on its own. Jul 23, 2025 · Using jsonify () is generally easier and more convenient than using json. This is to effectively mimic application making an outbound HTTP call or database call. seeing everything in) those other namespaces. So we don't want to keep the user waiting Nov 15, 2023 · Use Asyc Functions in Flask using Threading | Handle Open AI Long Delays & Timeout in Flask API UBprogrammer 2. run(threaded=True) and my server Also, as I said in my OP, I manage to start a single thread for my function within flask without interrupting flask. Jun 5, 2019 · 0 Found that if I switch out threading for multiprocessing (and threading. Create Python Flask App that sleeps for two seconds and responds with message ' Finished '. Here is a link conjugating it in all its tenseful glory. active_count () could you see if your version of the AioRTC code with Flask closes everything properly, even after, say a 24 hour stream? Oct 18, 2022 · I'm using "flask-socketio" package in my project with "threading" async_mode option and everything is working but on disconnection it throws an Exception. 4. 7. Risks and Mitigations While using multiple threads can alleviate the Feb 10, 2023 · Hi I have a flask app which needs to run a background task at certain intervals,I have tried to achieve this by using threading. Mar 8, 2017 · User kokos answered the wonderful Hidden Features of C# question by mentioning the using keyword. Apr 1, 2019 · Are you using eventlet or gevent? I'm not sure if Timer is compatible with green threads, that could be the problem. A helper library to work with threads in Flask. Gevent and Eventlet provide higher scalability than threads, but the cost is that the asynchronous programming model is harder to set up, as you need to Jun 7, 2020 · I was using asyncio inside a view function for Flask to run some asynchronous functions and met an error. Gunicorn allow to fork multiple instances of Flask. 1, flask-socketio1. When t1 = threading. I use Python threading to parallelize the image and OCR processing but even so the total processing can take 10 to 20 sec. I also do know that I can run Flask in main thread, and I am NOT Using debugging. Though the flask documentation provides the basic config, this guide is one I've used and it gives a much-more in-depth walkthrough for installation. Web Automation 3. The syntax is {module_import}:{app_variable}. The bigger problem is that Python doesn't utilize multiple CPU cores. A typical use case for threading includes managing a pool of worker threads that can process multiple tasks concurrently. For this purpose, we’ll be using the Python threading module to create a thread that generates random numbers regularly, and emits the newest value to all connected clients. gunicorn). The frontend polls the backend for progress updates while the task runs in a background thread. Why not put in some other wonky tenses? I will have used cocaine. Using flask's development server, I can use app. route("/hello") def Hello(): thread = threading. I'm afraid that the service will crash at some n t Running ¶ The only required argument to Gunicorn tells it how to load your Flask application. py, we define a thread object that will continually create random numbers and emit them using socketIO separately to the main flask process: Feb 23, 2020 · Learn all how you can stream real-time video with the Raspberry Pi camera and a Jetson Nano using the Flask framework! This library provides instrumentation for the threading module to ensure that the OpenTelemetry context is propagated across threads. They are Jun 8, 2012 · 45 Flask will process one request per thread at the same time. Nov 24, 2024 · By employing the threading module, you can easily run some code without blocking the main application thread, allowing your Flask app to remain responsive while executing background tasks. Thread, threading. I have tkinter running in the main thread, flask running in a seperate thread, and everything is working swimmingly except it doesn't run the command to insert the data into the GUI. I have… Feb 7, 2022 · 0 I'm trying to understand seemingly inconsistent performance of a Python Flask app on Google Cloud Run. The identifier following the using keyword becomes a typedef-name and the optional attribute-specifier-seq following the identifier appertains to that typedef-name. The issue is my server needs to handle lots of request coming to it and so I assigned multiple workers in gunicorn to handle it but when I do that my background task gives inconsistent result,for a certain time interval it should be executed only once but sometimes it Jul 10, 2015 · How can I update a flask session inside a python thread? The below code is throwing this error: *** RuntimeError: working outside of request context from flask import session def test(ses): May 14, 2015 · I am using Flask as service for requests that execute heavy processing tasks. The problem with putting using namespace in the header files of your classes is that it forces anyone who wants to use your classes (by including your header files) to also be 'using' (i. This allows your main Flask application thread to continue processing other requests while the background threads work independently. Nov 2, 2022 · Got a question, using threading. 0 and this runs the server in multi-threaded mode. Jan 4, 2016 · I am using Python 3. The app takes an image file as input and does some pre-processing using cv2 and then OCR using Tesseract. If you have 2 processes with 4 threads each, that's 8 concurrent requests. Aug 6, 2015 · I'm having a look at a couple of the new features in C# 6, specifically, "using static". Feb 26, 2015 · @BlackMamba : @methane 's answer explained the reason, using t = threading. start() method. Method 4: Using the before first request Decorator If you need your function to execute as soon as the first request is made after the app starts, you can utilize the before_first_request decorator: Nov 6, 2024 · Explore methods to handle state management in Flask applications and understand the implications of using global variables in a multi-threaded environment. As suggested by everyone, I can't use Flask in production. Since an image maybe not ready (is still rendering), I wrote the following code to wait for a rendering thread un Sep 18, 2023 · Approaching Flask in this way has numerous advantages. This sample can be copied and pasted in a . Jun 1, 2013 · I know that using threading can let these two functions independently of each other, but I have learnt programming for a very short time so I have no experience in threading programming, Could anybody provide some ideas or code examples for me at this problem? python flask asked Jun 1, 2013 at 8:44 Ying. I rarely use Exception in my catch es. So I am stuck, but I need to have background threads to keep my web server responsive. How can I change it? Unfortunately, it's my first time using threading and I'm having some issues getting ngrok/flask and tkinter to run concurrently. Here's an example of how you can start your Flask web in a separate thread: Aug 31, 2023 · We will learn how to configure Gunicorn to efficiently handle multiple concurrent requests for a Flask App on Azure App Service Linux. However, you may feel free to put a using statement in your (private) *. Apr 1, 2025 · This Flask application demonstrates web-based progress tracking. I want to use multi threading. For your use case, if you can speed up the individual image processing using threading or multiprocessing, you can choose to do that. 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 Dec 4, 2017 · Weekend Project (Part 2): Turning Flask into a real-time websocket server using Flask-SocketIO If you haven’t already, you can read Part 1 of this series here. If the following code is being run locally, Flask immediately returns the response and a few seconds later "Task done" appears in the logs. Updating the using keyword was specifically for templates, and (as was pointed out in the accepted answer) when you are working with non-templates using and typedef are mechanically identical, so the choice is totally up to the programmer on the grounds of readability and communication of intent. How does Flask ensure that `request` remains thread-safe, even when hundreds of requests are processed concurrently? Python isn't a real multithreaded language Python threads have limitations but they are real (otherwise Flask would freeze if one of the requests is blocked). Flask-SocketIO supports a variety of web servers that support WebSocket. g. ” Flask checks the URL the user visits and executes the matching function. Thread(target=long_running_task) thread. Flask Streaming Server 4. I dunno what kind of threading Flask is using, but Python can only run one native Python thread at a time. How to get rid of this leak ? 2 days ago · Using Flask This method use Flask framework only. Getting Started ¶ Initialization ¶ The following code example shows how to add Flask-SocketIO to a Flask application: Dec 27, 2019 · Deploy Flask application using Flask dev server The easiest way to run a Flask application is to use a built-in development server. It also allows heavy computation tasks to run in the background while keeping the application responsive. 1. Zhao 164314 3 Answers Sorted by: 5 Apr 25, 2022 · Hello world! I'm trying to help out a friend with this problem that I couldn't figure out. Thread for multiprocessing. Hi! Is there any way to enable multi-thread in a python flask app? app. What's reputation and how do I get it? Instead, you can save this post to reference later. Create and Start Thread A thread can be created using the Thread class provided by the threading module. Thread Management Running the Code and Viewing the Stream Using SSH Tunnel Applications and Considerations Conclusion Full Code Selenium makes it easy to automate your browser and take control of web pages for testing and automation May 28, 2021 · You'll need to complete a few actions and gain 15 reputation points before being able to upvote. cpp files. Timer, or Feb 9, 2020 · flask. Can you elaborate on that? What are the uses of using? In other word, if you know that the initialization of a variable in using may throw a particular exception, I wrap it with try-catch. the request handling becomes sequential. Dec 27, 2013 · 182 In C++11, the using keyword when used for type alias is identical to typedef. e. 10. start() is used the passed function will be called in the new thread and start the app there. json. Feb 25, 2016 · A really good way of setting this up would be to use "uwsgi" as your application server (and protocol) and Nginx as your front-end proxy. It can also be a function call (with any arguments) if you’re using the app factory pattern. cache simultaneously). Jun 29, 2024 · Centralized Logging System in Flask: The Backbone of Multithreaded Python Applications — In-Depth Guide In the ever-evolving landscape of software development, the importance of robust logging … 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. Flask. Selenium WebDriver Setup 2. Nov 13, 2023 · Python provides a module called threading that provides a high-level threading interface to create and manage threads in Python programs. Here, API is created using regular functions called “routes. Since you’re reading this blog … Jul 2, 2019 · Thank you, it looks like it has been asked about debug, I am wondering about threading. Nov 5, 2021 · Have you tried fixing it using the schedule package? For an example see this post: Python script to do something at the same time every day For running a scheduler in the background (i. WSGI servers will use multiple threads and/or processes for better performance and using connection pools in I have web application written in Flask. cxstbgrzvlcarxkzrjtcktoxiccmfdlcrmbrhjwewyhesbzhxbgixcnxulljokiudtjqf