How to Run a Flask Project in IIS: A Step-by-Step Guide

In my work, I encountered the challenge of deploying a Flask project on Windows, but I was unsure how to proceed. After searching online, I found that many articles were unhelpful. However, I eventually discovered the solution, and I would like to share how I successfully accomplished it.

Running a Flask application on Internet Information Services (IIS) is a great way to host Python web applications on a Windows server. IIS is a flexible, secure, and manageable web server for hosting anything on the web. In this article, we will walk through the process of setting up and running a Flask project in IIS with practical examples.

Prerequisites

Step 1: Install IIS and Configure CGI

1. Install IIS: If IIS is not already installed, you can install it by opening the Control Panel → Programs and Features → Turn Windows features on or off. Check the box for Internet Information Services and select OK.

2. Enable CGI: Under the same IIS features, ensure that CGI is installed. This allows IIS to execute Python scripts.

   • Go to Control Panel → Programs and Features → Turn Windows features on or off.
   • Expand Internet Information Services → Web Management Console
   • Expand Internet Information Services → World Wide Web Services → Application Development Features.
   • Check CGI and select OK.

            

Step 2: Install Python and Set Up Your Flask Application

1. Install Python: Download and install Python from the official website (https://www.python.org/downloads/). Make sure to add Python to the system PATH during installation.

2. Install Flask: Open a command prompt and run the following command: 

        pip install flask

      3. Create a Simple Flask App: Create a new directory for your Flask app and navigate to it. Create a Python file (app.py) with the following                      content:

        

    4. Run the app.py file and navigate to http://127.0.0.1:5000/ in your browser.

      

 

Step 3: Set Up FastCGI for Python

1. Install wfastcgi: wfastcgi is a Python package that enables FastCGI for IIS. Install it using pip:

   pip install wfastcgi
   

2. Configure wfastcgi: After installing, run the following command to configure wfastcgi:

wfastcgi-enable

            

Step 4: Configure IIS for Your Flask Application

1. Create a New Website in IIS:

   • Open IIS Manager.
   • In the Connections pane, right-click Sites → Add Website.
   • Enter a site name (e.g., "FlaskApp").
   • Set the Physical path to the directory where your Flask app resides.
   • Choose a Port (e.g.,5010 or another available port).
   • Click OK to create the website.
   • 

2. Add a Handler Mapping:

   • In IIS Manager, select your new site.
   • Double-click Handler Mappings.
   • On the right, click Add Module Mapping....
   • Enter the following settings:
     • Request path: *
     • Module: FastCgiModule
     • Executable: "C:\Program Files\Python312\python.exe"|"C:\Program Files\Python312\Lib\site-packages\wfastcgi.py" (your executable from step 3)
     • Name: FastApiHandler
     • Click on Request Restrictions..
       • Uncheck "Invoke handler only if request is mappeed to"
       • 
   • Click OK.
   • 
   • 
   • Click Yes

3. Configure FastCGI Settings:

   • Click on FastCGI Settings in IIS Manager (available in the Features view).
   • Find the entry for python.exe and select it.
   • Click Edit... on the right-hand side.
   • 
   • Add an environment variable with the following values:
     • Key: PYTHONPATH
     • Value: C:\Users\Alex\Documents\web_demo (yours path dir)
     • Key: WSGI_HANDLER
     • Value: app.app
     • 
   • Click OK to save.

Step 5: Test Your Flask Application

1. Start Your IIS Website: Ensure that your newly created site is running in IIS Manager.

2. Access Your Application: Open a web browser and navigate to http://127.0.0.1:5000/ or the IP address and port you configured. You should see your Flask app running with the

   {"email":"alex@mail.com","name":"Alex"}

   message.

Conclusion

You've successfully set up and run a Flask application in IIS using FastCGI. This setup is suitable for deploying Python web applications in a Windows environment where IIS is the preferred web server. With the power of IIS and the flexibility of Flask, you can now serve Python-based web applications in a production-ready environment.

Troubleshooting Tips

• Permission Issues: Ensure that the IIS user has permission to access the Python executable and your Flask application files.
  • Navigate to the directory of your Flask app, right-click, and select "Properties." Then, go to the "Security" tab and click "Edit." In the dialog that appears, click "Add" and enter IIS_IUSRS.
  •