The way in which distributed systems communicate with each other is crucial to their efficiency, reliability, and overall functionality. REST (Representational State Transfer) and RPC (Remote Procedure Call) are prominent communication paradigms.
REST and RPC allow different systems or components to talk to each other. However, they have fundamental differences in philosophy, design, and application.
This tutorial highlights the differences between REST and RPC, uncovering their histories, principles, advantages, and disadvantages.
2. Historical Context
The differences in the origins of REST and RPC highlight the evolution of web communication and emphasize the challenges and environments each was designed to address.
2.1. Short History of RPC (Remote Procedure Call)
The concept of RPC dates back to the early days of distributed computing. Systems needed a way to execute procedures or functions on remote machines, essentially making a call as if it were a local procedure.
The RPC systems began taking shape in the 1980s with the introduction of SunRPC, developed by Sun Microsystems. As the internet evolved, RPC’s capabilities grew. This led to the development of variations like XML-RPC, which allowed for remote calls using XML over HTTP and later JSON-RPC.
2.2. Emergence of REST (Representational State Transfer)
Dr. Roy Fielding introduced REST in his 2000 doctoral dissertation. Instead of focusing on actions or methods, as in RPC, REST centers on resources. Fielding emphasized using the web’s inherent capabilities, particularly HTTP’s stateless requests and standardized methods.
Given its simplicity and alignment with the web’s principles, REST quickly gained traction. It became the standard for public APIs on the web. While RESTful principles are still highly prevalent, there’s a growing movement towards more flexible and efficient protocols, especially in specific use cases where REST might not be optimal.
3. Basic Definitions
Let’s overview the basic definitions and characteristics of both REST and RPC.
REST is an architectural style. It provides a set of constraints that enable systems to achieve properties like performance, scalability, and modifiability.
At its core, REST is about representing and manipulating resources on the web. A resource can be anything – an object, a service, a piece of data – and it’s uniquely identified by its URI.
RPC is a protocol that a program can use to request a service from a program located on another computer. It allows a program to cause a procedure or subroutine to execute on another address space, usually another computer on a shared network. It’s similar to calling a method on an object that exists on a different machine.
4. Communication Model
The way in which data is transferred, and the conventions used for such communication differentiate REST and RPC significantly. Let’s dissect the respective communication models of each.
REST harnesses the power and simplicity of the HTTP protocol for communication, relying on its standardized set of methods. These standard HTTP verbs ensure uniformity and predictability in interactions.
Due to stateless communication, each request from a client to a server must contain all the information needed to understand and process the request. This makes interactions clear-cut, without any need to maintain a session state on the server.
RPC’s model is more about invoking actions. Its method calls are more verbose, indicating specific procedures.
RPC is like calling a function. The client specifies the procedure to execute along with the parameters, and the server returns the results. This might appear more direct and granular compared to the resource-based approach.
An essential aspect to note is that RPC might seem tightly coupled because of its procedural nature. Modern implementations like gRPC are built with flexibility and efficiency in mind, allowing for more scalable and loosely coupled systems.
5. Addressing Resources
How systems identify and address the data or services they interact with is central to their design and functionality. The paradigms of REST and RPC have distinct ways of approaching this.
In the RESTful world, everything revolves around the concept of resources. Every resource in a RESTful system is uniquely identified by its URI. This design choice provides a straightforward way to locate, manipulate, and interact with entities on the web.
In REST, it’s not just about identifying the resource but also about how we represent it. Common representations include JSON and XML, among others. The idea is to interact with the resource using these representations via standard HTTP methods.
RPC revolves around invoking procedures or methods. In RPC, we call a specific method provided by the server. The method name and parameters are central to the request. There’s no standard like URIs in REST. Instead, the method name and its signature become the defining aspect.
Parameters can be passed by name or by position, and the method naming usually mirrors the function it’s trying to achieve on the server side. While this can be seen as flexible, it can also lead to challenges with versioning and changing method signatures over time.
6. Data Formats
The representation and structure of data being transmitted play a pivotal role in the clarity, efficiency, and performance of communication. Both REST and RPC employ different strategies for this.
REST is agnostic to the data format, but there are popular conventions that have been widely adopted in the industry. The majority of RESTful services use JSON due to its lightweight nature and ease of use. XML was more prevalent in earlier implementations, especially with SOAP-based services, but has seen a decline in favor of JSON.
The beauty of REST is that we can choose the representation that best fits our needs. For instance, while JSON and XML are common, some systems might use YAML, HTML, or even custom formats.
The data format in RPC largely depends on the type and specifications of the RPC protocol being used.
In newer RPC protocols like gRPC, performance is strongly emphasized. Protobuf, for example, is smaller and faster than JSON and XML. This can lead to significant performance gains, especially in systems with high-throughput requirements.
7. Comparing REST and RPC
Every architectural style or protocol has its own set of advantages and trade-offs. Understanding these can aid developers in selecting the right approach for their specific use cases.
Let’s review the pros and cons of REST architecture:
Also, we can list same advantages and disadvantages of RPC as well:
To conclude, neither REST nor RPC is a silver bullet. They cater to different needs and scenarios, and understanding their strengths and limitations is crucial. The right choice often emerges from a thorough analysis of our project’s requirements, objectives, and potential evolutions.