Gunicorn Deployment Guide for Flask Applications

How to deploy Flask application using Gunicorn?

Flask is a lightweight Python Web framework that is widely used to develop various types of Web applications. Gunicorn (Green Unicorn) is a Python-based HTTP server used to run WSGI (Web Server Gateway Interface) applications. This article will introduce how to use Gunicorn to deploy Flask applications, and attach specific code examples.

Step 1: Install dependencies

Before we start, we need to make sure that python and pip tools have been installed in the system. Open a terminal and execute the following command to install Flask and Gunicorn:

$ pip install flask gunicorn

Step 2: Create a Flask application

Create a file named app.py in the project directory Python file, select a simple sample application to demonstrate Gunicorn deployment. The following is a code example for a simple Flask application:

from flask import Flask

app = Flask(__name__)

@app.route('/')
def hello():
    return "Hello, Flask!"

if __name__ == '__main__':
    app.run()

The above code creates a Flask application named app and returns a simple Hello message on the root route.

Step 3: Test the Flask application

Execute the following command in the terminal to test whether the Flask application is running properly:

$ python app.py

If everything goes well, you should be able to See output similar to the following:

 * Running on http://127.0.0.1:5000/ (Press CTRL+C to quit)

Now, we have verified that the Flask application works properly.

Step 4: Use Gunicorn to start the application

Now we can use Gunicorn to start the Flask application. Execute the following command in the terminal:

$ gunicorn app:app

In the above command, app:app means that the application to be started is app# in the app.py file ##Object.

If all goes well, you should be able to see output similar to the following in the terminal:

[2021-01-01 12:00:00 +0000] [12345] [INFO] Starting gunicorn 20.0.4
[2021-01-01 12:00:00 +0000] [12345] [INFO] Listening at: http://127.0.0.1:8000 (12345)
[2021-01-01 12:00:00 +0000] [12345] [INFO] Using worker: sync
[2021-01-01 12:00:00 +0000] [12345] [INFO] Booting worker with pid: 67890

Step 5: Test the Gunicorn deployed application

Now, we need to test Let’s see if Gunicorn successfully deployed our Flask application. Open the following address in the browser:

http://127.0.0.1:8000/

If everything goes well, you should be able to see the "Hello, Flask!" information returned by the Flask application we defined previously displayed on the browser page.

Conclusion

Through the above simple steps, we successfully used Gunicorn to deploy Flask applications. Gunicorn provides high-performance, stable and scalable services that can provide better performance and availability for Flask applications. I hope this article can help you successfully deploy your Flask application.

Reference link

Flask official documentation: https://flask.palletsprojects.com/
• Gunicorn official documentation: https://gunicorn.org/

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