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Mastering WSGI Servers: A Vital Component of Python Web Development

Introduction to WSGI Servers

If you’re a web developer, then you have likely heard of the term WSGI server. However, not everyone may be familiar with what it is and how it functions.

Simply put, a WSGI server is a Python-based web server that handles requests and generates responses. In this article, we will delve into the process of handling requests and providing responses, the use of workers to handle multiple requests simultaneously, and the recommended number of workers based on server resources.

Process of Handling Requests and Providing Responses

When a user sends a request to a website, the WSGI server begins the process of handling the request. It takes the request and sends it to the appropriate application or function.

In Python, this is typically done with a WSGI application or function. The function then processes the request and generates a response.

The response is then returned to the WSGI server, which sends it back to the user’s browser. This process is repeated every time a new request is made to the web server.

Use of Workers to Handle Multiple Requests Simultaneously

As websites become more popular, the number of requests that a WSGI server must handle simultaneously will increase. This can lead to user frustration as requests take longer to process.

To handle multiple requests at once, web servers use workers. Workers are separate processes that handle requests independently of each other.

By using multiple workers, a WSGI server can handle multiple requests simultaneously, improving performance and user experience.

Recommended Number of Workers Based on Server Resources

The number of workers a WSGI server should use depends on the resources available on the server. If there are not enough workers, requests will take longer to process.

However, if there are too many workers, the server will become overloaded, leading to slower performance. To determine the appropriate number of workers, web developers should perform load testing.

Load testing involves simulating a high number of requests to the server to determine how many workers are needed to handle the load effectively.

Creating a WSGI Server in Flask

Now that you have a basic understanding of what a WSGI server does let’s move on to creating our own WSGI server using Flask.

Setting up Directory and Importing Necessary Packages

To get started, we need to set up our directory and import the necessary packages. We will be using Flask, a Python-based web framework, and wsgiref, a reference implementation of the WSGI server interface.

First, create a new directory for your project and navigate inside of it. Next, create a new file called app.py, which will contain our web application.

From here, we will import the necessary packages by adding the following code to the top of our app.py file:


from flask import Flask

from wsgiref.simple_server import make_server


Defining a Function-Based Web App Using Environment and Response Parameters

Next, we need to define our web application using Flask. Flask allows us to create a web application using a function.

Our function will take two parameters: environ and start_response. The environ parameter represents the environment variables that are sent with the request, while the start_response parameter is a function that we will use to set the status and headers of the response.

Here’s an example of how our function would look:


def app(environ, start_response):

status = ‘200 OK’

headers = [(‘Content-type’, ‘text/plain’)]

start_response(status, headers)

return [b’Hello, world!’]


Creating Status and Headers to Set the Response

In our example function, we have set the status to ‘200 OK’ and set the content type to ‘text/plain’. We then used the start_response function to set the status and headers.

The last line of our function returns the response data, which in this case is simply ‘Hello, world!’.

Serving the App Using make_server() Function and serve_forever() Method

Now that we have defined our web application, we need to serve it using a WSGI server. Flask includes a built-in WSGI server, but for the purposes of this article, we will use wsgiref’s make_server() and serve_forever() functions.

We can serve our application using the following code:


if __name__ == ‘__main__’:

httpd = make_server(”, 8000, app)

print(“Serving on port 8000…”)



This code will create a new WSGI server listening on port 8000 and serving our app function.


In conclusion, WSGI servers are a crucial component of web development in Python. By using workers to handle multiple requests simultaneously and determining the appropriate number of workers based on server resources, developers can ensure that their websites are both performant and scalable.

By creating a WSGI server in Flask, web developers can gain a deeper understanding of how WSGI servers work and how to create them in a Python environment.

Importance of Understanding and Creating WSGI Servers

Web developers are often concerned with creating web applications that are both performant and scalable. To achieve this, many use a WSGI (Web Server Gateway Interface) server.

A WSGI server is responsible for handling requests and generating responses, which makes it an indispensable part of web development. Understanding how a WSGI server works and how to create one is essential for any web developer.

A WSGI server allows developers to handle multiple requests simultaneously, thereby improving website performance. It also gives developers more control over how their web applications work, making them more architecture-friendly.

Several powerful Python web frameworks, like Flask, Pyramid, and Django, come with built-in WSGI support, allowing developers to create servers quickly and without too much code. Additionally, WSGI servers are also compatible with other languages like Ruby, Java, and PHP.

Creating a WSGI server can be a challenging, but rewarding process for programmers. By building a server from the ground up, a programmer gains a deeper understanding of how web applications work and how to customize them.

This understanding better equips developers to debug errors, improve performance, and build more reliable web applications.

Additional Resources for Learning More About WSGI Servers

For those looking to learn more about WSGI servers, there are plenty of resources available online, including tutorial videos, online courses, and documentation.

The Python documentation contains an extensive section on writing WSGI applications, which can be a helpful starting point for beginners.

The Flask documentation, in particular, has a detailed guide on creating a WSGI server, which developers can use to follow a step-by-step process. Pluralsight is a popular online learning platform that offers a comprehensive course on WSGI, covering everything from understanding the basics to advanced configuration.

Udemy is another popular online learning platform that offers courses on creating WSGI servers in Python. For those who prefer video tutorials, the popular YouTube channel, Corey Schafer, has several WSGI-related videos, including a tutorial on creating a WSGI server in Flask.

Finally, joining online forums where web developers discuss their experiences with WSGI servers and share knowledge can be an excellent way to learn. These forums include Reddit’s r/webdev, Stack Overflow and open source communities like Apache, providing a wealth of knowledge and resources for developers.


A WSGI server is a vital part of any developer’s toolkit, and learning how to create one can be a challenging but rewarding experience. By building a WSGI server, developers can gain a more profound understanding of how web applications work and how to improve their website’s performance and scalability.

There are several resources available online for developers who want to learn more about WSGI servers, including documentation, online courses, video tutorials, and online communities. As web development continues to grow and innovate, WSGI servers will remain a critical part of web development, so it’s essential for developers to stay up-to-date with the latest techniques and improve their skills regularly.

In conclusion, WSGI servers are essential for web development in Python. They handle requests, generate responses, and improve website performance.

By using workers and determining the appropriate number of workers based on server resources, developers can ensure their web applications are scalable and performant. Creating a WSGI server in Flask helps developers gain a deeper understanding of how WSGI servers work and how to customize them.

With a range of resources available for learning, from Python documentation to online courses, mastering WSGI servers is more accessible than ever. Overall, WSGI servers are a vital part of web development and can help developers build more reliable web applications.

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