Web service differences between REST and RPC

I have a web service that accepts JSON parameters and have specific URLs for methods, e.g.:

http://IP:PORT/API/getAllData?p={JSON}

This is definitely not REST as it is not stateless. It takes cookies into account and has its own session.

Is it RPC? What is the difference between RPC and REST?

Consider the following example of HTTP APIs that model orders being placed in a restaurant.

• The RPC API thinks in terms of "verbs", exposing the restaurant functionality as function calls that accept parameters, and invokes these functions via the HTTP verb that seems most appropriate - a 'get' for a query, and so on, but the name of the verb is purely incidental and has no real bearing on the actual functionality, since you're calling a different URL each time. Return codes are hand-coded, and part of the service contract.
• The REST API, in contrast, models the various entities within the problem domain as resources, and uses HTTP verbs to represent transactions against these resources - POST to create, PUT to update, and GET to read. All of these verbs, invoked on the same URL, provide different functionality. Common HTTP return codes are used to convey status of the requests.

Placing an Order:

• RPC: http://MyRestaurant:8080/Orders/PlaceOrder (POST: {Tacos object})
• REST: http://MyRestaurant:8080/Orders/Order?OrderNumber=asdf (POST: {Tacos object})

Retrieving an Order:

• RPC: http://MyRestaurant:8080/Orders/GetOrder?OrderNumber=asdf (GET)
• REST: http://MyRestaurant:8080/Orders/Order?OrderNumber=asdf (GET)

Updating an Order:

• RPC: http://MyRestaurant:8080/Orders/UpdateOrder (PUT: {Pineapple Tacos object})
• REST: http://MyRestaurant:8080/Orders/Order?OrderNumber=asdf (PUT: {Pineapple Tacos object})

Example taken from sites.google.com/site/wagingguerillasoftware/rest-series/what-is-restful-rest-vs-rpc

You can't make a clear separation between REST or RPC just by looking at what you posted.

One constraint of REST is that it has to be stateless. If you have a session then you have state so you can't call your service RESTful.

The fact that you have an action in your URL (i.e. getAllData) is an indication towards RPC. In REST you exchange representations and the operation you perform is dictated by the HTTP verbs. Also, in REST, Content negotiation isn't performed with a ?p={JSON} parameter.

Don't know if your service is RPC, but it is not RESTful. You can learn about the difference online, here's an article to get you started: Debunking the Myths of RPC & REST. You know better what's inside your service so compare it's functions to what RPC is and draw your own conclusions.

As others have said, a key difference is that REST URLs are noun-centric and RPC URLs are verb-centric. I just wanted to include this clear table of examples demonstrating that:

---------------------------+-------------------------------------+--------------------------
Operation                 | RPC (operation)                     | REST (resource)
---------------------------+-------------------------------------+--------------------------
Signup                    | POST /signup                        | POST /persons

---------------------------+-------------------------------------+--------------------------
Resign                    | POST /resign                        | DELETE /persons/1234

---------------------------+-------------------------------------+--------------------------
Read person               | GET /readPerson?personid=1234       | GET /persons/1234

---------------------------+-------------------------------------+--------------------------
Read person's items list  | GET /readUsersItemsList?userid=1234 | GET /persons/1234/items
---------------------------+-------------------------------------+--------------------------
Add item to person's list | POST /addItemToUsersItemsList       | POST /persons/1234/items
---------------------------+-------------------------------------+--------------------------
Update item               | POST /modifyItem                    | PUT /items/456

---------------------------+-------------------------------------+--------------------------
Delete item               | POST /removeItem?itemId=456         | DELETE /items/456

---------------------------+-------------------------------------+--------------------------

Notes

• As the table shows, REST tends to use URL path parameters to identify specific resources
  (e.g. GET /persons/1234), whereas RPC tends to use query parameters for function inputs
  (e.g. GET /readPerson?personid=1234).

• Not shown in the table is how a REST API would handle filtering, which would typically involve query parameters (e.g. GET /persons?height=tall).

• Also not shown is how with either system, when you do create/update operations, additional data is probably passed in via the message body (e.g. when you do POST /signup or POST /persons, you include data describing the new person).

• Of course, none of this is set in stone, but it gives you an idea of what you are likely to encounter and how you might want to organize your own API for consistency. For further discussion of REST URL design, see this question.

It is RPC using http. A correct implementation of REST should be different from RPC. To have a logic to process data, like a method/function, is RPC. getAllData() is an intelligent method. REST cannot have intelligence, it should be dumb data that can be queried by an external intelligence.

Most implementation I have seen these days are RPC but many mistakenly call it as REST. REST with HTTP is the saviour and SOAP with XML the villain. So your confusion is justified and you are right, it is not REST. But keep in mind that REST is not new(2000) eventhough SOAP/XML is old, json-rpc came later(2005).

Http protocol does not make an implementation of REST. Both REST(GET, POST, PUT, PATCH, DELETE) and RPC(GET + POST) can be developed through HTTP(eg:through a web API project in visual studio for example).

Fine, but what is REST then? Richardson maturity model is given below(summarized). Only level 3 is RESTful.

• Level 0: Http POST
• Level 1: each resource/entity has a URI (but still only POST)
• Level 2: Both POST and GET can be used
• Level 3(RESTful): Uses HATEOAS (hyper media links) or in other words self exploratory links

eg: level 3(HATEOAS):

1. Link states this object can be updated this way, and added this way.

2. Link states this object can only be read and this is how we do it.

   Clearly, sending data is not enough to become REST, but how to query the data, should be mentioned too. But then again, why the 4 steps? Why can't it be just Step 4 and call it REST? Richardson just gave us a step by step approach to get there, that is all.

> You've built web sites that can be used by humans. But can you also > build web sites that are usable by machines? That's where the future > lies, and RESTful Web Services shows you how to do it.

• This book RESTful Web Services helps

• A very interesting read RPC vs REST

REST is best described to work with the resources, where as RPC is more about the actions.

REST stands for Representational State Transfer. It is a simple way to organize interactions between independent systems. RESTful applications commonly use HTTP requests to post data (create and/or update), read data (e.g., make queries), and delete data. Thus, REST can use HTTP for all four CRUD (Create/Read/Update/Delete) operations.

RPC is basically used to communicate across the different modules to serve user requests. e.g. In openstack like how nova, glance and neutron work together when booting a virtual machine.

The URL shared looks like RPC endpoint. Below are examples for both RPC and REST. Hopefully this helps in understanding when they can be used.

Lets consider an endpoint that sends app maintenance outage emails to customers.

This endpoint preforms one specific action.

RPC

POST https://localhost:8080/sendOutageEmails

BODY: {"message": "we have a scheduled system downtime today at 1 AM"}

REST

POST https://localhost:8080/emails/outage

BODY: {"message": "we have a scheduled system downtime today at 1 AM"}

RPC endpoint is more suitable to use in this case. RPC endpoints usually are used when the API call is performing single task or action. We can obviously use REST as shown, but the endpoint is not very RESTful since we are not performing operations on resources.

Now lets look at an endpoint that stores some data in the database.(typical CRUD operation)

RPC

POST https://localhost:8080/saveBookDetails

BODY: {"id": "123", "name": "book1", "year": "2020"}

REST

POST https://localhost:8080/books

BODY: {"id": "123", "name": "book1", "year": "2020"}

REST is much better for cases like this(CRUD). Here, read(GET) or delete(DELETE) or update(PUT) can be done by using appropriate HTTP methods. Methods decide the operation on the resources(in this case 'books'). Using RPC here is not suitable as we need to have different paths for each CRUD operation(/getBookDetails, /deleteBookDetails, /updateBookDetails) and this has to be done for all resources in the application.

To summarize,

• RPC can be used for endpoints that perform single specific action.
• REST for endpoints where the resources need CRUD operations.

I would argue thusly:

Does my entity hold/own the data? Then RPC: here is a copy of some of my data, manipulate the data copy I send to you and return to me a copy of your result.

Does the called entity hold/own the data? Then REST: either (1) show me a copy of some of your data or (2) manipulate some of your data.

Ultimately it is about which "side" of the action owns/holds the data. And yes, you can use REST verbiage to talk to an RPC-based system, but you will still be doing RPC activity when doing so.

Example 1: I have an object that is communicating to a relational database store (or any other type of data store) via a DAO. Makes sense to use REST style for that interaction between my object and the data access object which can exist as an API. My entity does not own/hold the data, the relational database (or non-relational data store) does.

Example 2: I need to do a lot of complex math. I don't want to load a bunch of math methods into my object, I just want to pass some values to something else that can do all kinds of math, and get a result. Then RPC style makes sense, because the math object/entity will expose to my object a whole bunch of operations. Note that these methods might all be exposed as individual APIs and I might call any of them with GET. I can even claim this is RESTful because I am calling via HTTP GET but really under the covers it is RPC. My entity owns/holds the data, the remote entity is just performing manipulations on the copies of the data that I sent to it.

Over HTTP they both end up being just HttpRequest objects and they both expect a HttpResponse object back. I think one can continue coding with that description and worry about something else.

There are bunch of good answers here. I would still refer you to this google blog as it does a really good job of discussing the differences between RPC & REST and captures something that I didn't read in any of the answers here.

I would quote a paragraph from the same link that stood out to me:

> REST itself is a description of the design principles that underpin HTTP and the world-wide web. But because HTTP is the only commercially important REST API, we can mostly avoid discussing REST and just focus on HTTP. This substitution is useful because there is a lot of confusion and variability in what people think REST means in the context of APIs, but there is much greater clarity and agreement on what HTTP itself is. The HTTP model is the perfect inverse of the RPC model—in the RPC model, the addressable units are procedures, and the entities of the problem domain are hidden behind the procedures. In the HTTP model, the addressable units are the entities themselves and the behaviors of the system are hidden behind the entities as side-effects of creating, updating, or deleting them.

This is how I understand and use them in different use cases:

Example: Restaurant Management

use-case for REST: order management

- create order (POST), update order (PATCH), cancel order (DELETE), retrieve order (GET)
- endpoint: /order?orderId=123

For resource management, REST is clean. One endpoint with pre-defined actions. It can be seen a way to expose a DB (Sql or NoSql) or class instances to the world.

Implementation Example:

class order:
    on_get(self, req, resp): doThis.
    on_patch(self, req, resp): doThat.

Framework Example: Falcon for python.

use-case for RPC: operation management

- prepare ingredients: /operation/clean/kitchen
- cook the order: /operation/cook/123
- serve the order /operation/serve/123

For analytical, operational, non-responsive, non-representative, action-based jobs, RPC works better and it is very natural to think functional.

Implementation Example:

@route('/operation/cook/<orderId>')
def cook(orderId): doThis.

@route('/operation/serve/<orderId>')
def serve(orderId): doThat.

Framework Example: Flask for python