Stateless-ness in RESTful APIs
In the intricate world of software architecture, the term “statelessness” stands as a fundamental principle, particularly in the realm of RESTful API design. Solutions Architects entrusted with the task of building or re-architecting platforms must navigate the nuances of statelessness to ensure the creation of scalable, performant, and resilient systems.
However, before we learn what Statelessness means within RESTful APIs, let’s take a moment to grasp the essence of APIs and RESTful APIs.
Understanding the Basics
API (Application Programming Interface)
An API defines rules that must be followed for software systems to communicate with each other. These are created by software developers who expose platforms to be programmatically accessible by other systems.
Key terms:
Client: The entity making use of information from the API.
Resource: Information provided by the API to the client. This is what is exposed to external use.
Server: Processes client requests and hosts the API containing desired resources.
HTTP request: The message a client sends to request information from a server.
RESTful API (REpresentational State Transfer)
REST is a standardised software architecture style facilitating communication between separate components. It is an interface or design pattern allowing secure information exchange over the internet. Coined by computer scientist Roy Fielding, RESTful APIs adhere to REST principles, offering simplicity, standardisation, scalability, high performance, and, crucially, statelessness (which is the main reason for this article).
Back to Statelessness in Restful APIs
Statelessness in the context of RESTful APIs signifies that each HTTP request operates in complete isolation from others, with the server not storing any client session state. When a client makes an HTTP request, it includes all necessary information for server processing, and the server reciprocates with information, enabling the client to create any required state.
In a scenario where we have two apps (app A talking to app B), app A brings its current state with it, and it doesn’t expect app B to maintain state-like process-based information between communication calls. App A supplies a representation of its relevant state with each request to app B. This increases reliability and resilience because if there is a communication issue or app B crashes and is restarted, it doesn’t lose the current state of its interactions with app A; App A can simply reissue the request and pick up from where the two apps left off.
Example of Statelessness
Suppose we have an API where we want to log in and order some goods; the API deployed on many servers can serve many requests, even from the same account, without storing the authentication details or provided token state. In a stateless environment, the server does not store the authentication/authorisation details of the client beforehand. These are provided, as well as other required information, with each request to the server. This approach ensures that even if a server becomes unreachable, the client can resend the request to another server instance and continue operations.
Advantages of Statelessness
- Scalability: Easy scaling of the API to millions of concurrent users through load balancing on multiple servers. Any server can handle requests because there is no session-related dependency.
- Simplified Design: Reduces complexity as servers don’t have to maintain previous interactions with clients.
- Improved Performance: Servers do not need to track client requests, enhancing overall performance.
- Reliability: Servers never lose track of client positions as clients provide all necessary information with each request.
Disadvantage of Statelessness
The main drawback is that requests must contain all necessary information and previous transactions, potentially leading to increased request sizes.
Closing thoughts
In the world of building software, understanding how statelessness works in RESTful APIs is crucial. It helps architects make systems that handle lots of user traffic, keep things simple, and run fast. While there’s a small downside with bigger requests, the good stuff, like reliability and speed, makes it totally worth it. By using statelessness smartly, architects set the stage for systems that can handle whatever the digital space throws at them.
Twitter handle: @KalemaEdgar
