REST versus RPC

Have you considered the merits and applicability of RESTful web apps? Here are a few notes I’ve made.

There was quite a [discussion about RPC, REST, and message queuing]( — they are not the same thing. Each one is needed in a different scenario. All are used in building distributed systems.

Wikipedia’s [explanation of REST]( is quite informative, especially their [examples]( of RPC versus REST.

The poster “soabloke” says RPC “Promotes tightly coupled systems which are difficult to
scale and maintain. Other abstractions have been more successful in building
distributed systems. One such abstraction is message queueing where systems
communicate with each other by passing messages through a distributed queue.
REST is another completely different abstraction based around the concept of a
‘Resource’. Message queuing can be used to simulate RPC-type calls
(request/reply) and REST might commonly use a request/reply protocol (HTTP) but
they are fundamentally different from RPC as most people conceive it. ”

The [REST FAQ]( says, “Most applications that self-identify as using “RPC” do not conform to the REST. In particular,
most use a single URL to represent the end-point (dispatch point) instead of using a multitude of
URLs representing every interesting data object. Then they hide their data objects behind method
calls and parameters, making them unavailable to applications built of the Web. REST-based
services give addresses to every useful data object and use the resources themselves as the
targets for method calls (typically using HTTP methods)… REST is incompatible with
‘end-point’ RPC. Either you address data objects (REST) or you don’t.”

RPC: Remote Procedure Call assumes that people agree on what kinds of procedures they would like
to do. RPC is about algorithms, code, etc. that operate on data, rather than about the data
itself. Usually fast. Usually binary encoded. Okay for software designed and consumed by a
single vendor.

REST: All data is addressed using URLs, and is encoded using a standard MIME type. Data that is
made up of other data would simply have URLs pointing to the other data. Assumes that people
won’t agree on what they want to do with data, so they let people get the data, and act on it
independently, without agreeing on procedures.