Why is HTTP stateless? 🤔

In this article, I will explain what is HTTP, what does it mean to be stateless, and why HTTP is designed to be stateless. I will also give some examples of how HTTP can be made stateful using cookies and sessions. 🚀

What is HTTP? 🌐

HTTP stands for Hypertext Transfer Protocol, and it is the basis of the web. HTTP defines how messages are formatted and transmitted between clients and servers over the Internet. HTTP messages consist of two types: requests and responses. Requests are sent from clients to servers to ask for a resource or a service, such as a web page, an image, a file, etc. Responses are sent from servers to clients to deliver the requested resource or service, or to indicate the status of the request, such as success, failure, redirection, etc.

What does it mean to be stateless? 🙅‍♂️

A protocol is said to be stateless if it does not keep track of the state or the history of the communication between the parties involved. In other words, each message is treated independently and separately from the previous or the next message. A protocol is said to be stateful if it does keep track of the state or the history of the communication between the parties involved. In other words, each message is related and dependent on the previous or the next message.

For example, consider a simple conversation between two people:

Person A: Hi, how are you?
Person B: I'm fine, thank you.
Person A: What's your name?
Person B: My name is Bob.

This conversation is stateful because each message depends on the previous message. Person B's answer to Person A's question depends on what Person A asked. If we change the order of the messages, the conversation does not make sense:

Person A: What's your name?
Person B: I'm fine, thank you.
Person A: Hi, how are you?
Person B: My name is Bob.

This conversation is stateless because each message does not depend on the previous message. Person B's answer to Person A's question does not depend on what Person A asked. If we change the order of the messages, the conversation still makes sense:

Person A: Hi, how are you?
Person B: My name is Bob.
Person A: What's your name?
Person B: I'm fine, thank you.

Why is HTTP designed to be stateless? 🤷‍♂️

HTTP is designed to be stateless because it has some advantages over being stateful, such as:

Simplicity: Stateless protocols are easier to implement and maintain than stateful protocols because they do not require storing and managing any information about the communication between clients and servers.
Scalability: Stateless protocols are more scalable than stateful protocols because they do not require any synchronization or coordination between clients and servers. Stateless protocols can also handle more concurrent requests and responses than stateful protocols because they do not consume any resources or memory on the servers.
Reliability: Stateless protocols are more reliable than stateful protocols because they do not depend on any previous or next message. Stateless protocols can handle any failure or interruption in the communication without affecting the outcome of the request or response.

However, HTTP being stateless also has some disadvantages, such as:

Lack of context: Stateless protocols do not have any context or history of the communication between clients and servers. This means that each request or response has to contain all the necessary information to complete the transaction, such as authentication, preferences, session data, etc. This can increase the size and complexity of the messages and reduce the performance and efficiency of the communication.
Lack of personalization: Stateless protocols do not have any memory or knowledge of the communication between clients and servers. This means that each request or response has to be treated equally and generically without any customization or adaptation based on the user's behavior, preferences, history, etc. This can reduce the user experience and satisfaction of the communication.

How can HTTP be made stateful using cookies and sessions? 🍪

HTTP can be made stateful using cookies and sessions, which are two techniques that allow storing and transferring some information about the communication between clients and servers.

Cookies are small pieces of data that are stored on the client's device by the server and sent back to the server with each request. Cookies can contain various information about the user's identity, preferences, history, etc. Cookies can make HTTP stateful by allowing the server to recognize and remember the user across multiple requests and responses.

Sessions are temporary storage spaces that are created on the server for each user who accesses a web application. Sessions can contain various information about the user's activity, data, status, etc. Sessions can make HTTP stateful by allowing the server to keep track and manage the user's interaction with a web application across multiple requests and responses.

The following diagram illustrates how cookies and sessions work together to make HTTP stateful:

sequenceDiagram
    participant Client
    participant Server
    Client->>Server: Request (without cookie)
    Server->>Server: Create session (with session ID)
    Server->>Client: Response (with cookie containing session ID)
    Client->>Server: Request (with cookie containing session ID)
    Server->>Server: Retrieve session (using session ID)
    Server->>Client: Response (with cookie containing session ID)

Conclusion 🎉

In this article, I have explained what is HTTP, what does it mean to be stateless, and why HTTP is designed to be stateless. I have also given some examples of how HTTP can be made stateful using cookies and sessions.

I hope you have learned something new and useful from this article 😊

If you have any questions or feedback, please feel free to leave a comment below 👇 Thank you for reading! 👋