Steve Vinoski’s Blog

My latest Internet Computing column has been available since last Friday. It’s entitled “RPC and REST: Dilemma, Disruption, and Displacement” (PDF, HTML) and like my previous 2008 columns, it explores another angle of the “RPC vs. REST” debate.

Since previous columns have covered many of the technical angles, this time I present the debate from the technology adoption angle. As the abstract for the column says, many technologists tend to treat such debates as if they’re purely technical, but of course they’re never that black-and-white. What’s often behind some of the raging “technical” debates we’ve all seen or experienced is simply the difference between the arguing parties in their relative positions along the Technology Adoption Lifecycle curve. Nobody would be surprised at a disagreement over technology between someone classified as an early adopter or visionary (from the far left of the curve) and someone classified as a technology skeptic (from the far right), yet we always seem surprised when two people whose preferences aren’t too far apart on the curve — from the opposite edges of the mainstream band in the middle of the bell curve, for example — don’t see eye to eye, despite the fact that this sort of scenario is quite common. Even small differences in goals for adopted technologies and desired risk/reward trade-offs, along with the inevitable hidden and unstated assumptions resulting from such factors, can cause vigorous debate about what technology or approach is best for a given situation.

When it comes to published explanations of how innovation works and how technologies move along the adoption curve, my favorite author by far is Clayton Christensen. IMO all developers should study and learn from his books, specifically The Innovator’s Dilemma, The Innovator’s Solution, and Seeing What’s Next. All are amazingly insightful works that will open your eyes to how real-life markets react to technological change and advancement.

In this column I try to view and classify the “RPC vs. REST” debate based on Christensen’s theories about innovation and technology adoption. I hope you find it interesting, and as always, I welcome all constructive comments.

I’ve noticed that frequently in technical discussions, the strongest disagreements seem to come from people with little to no actual experience with the technology they’re arguing against. How can that be? For example:

• Test-First Development. I wish I had a dollar for every time I’ve suggested to a developer that writing their tests before or along with writing their code will make the code not only easier to write but also more robust coming out of the gate, and I get back responses like, “What? That’s crazy! How can you write tests before you have any code? That doesn’t make any sense!” Having an initial reaction like that isn’t such a big deal, as I’ve seen numerous developers who have such reactions actually try the “test first” approach and quickly become strong advocates who wonder how they ever did without it. The point is, though, that they actually tried it. Arguing with them before they tried it always turned out to be a total waste of time. No amount of words seemed to convince them. They had to experience it before they understood it.

• Erlang syntax. Erlang is getting more and more attention these days, and rightfully so, but a typical reaction from those who have written little to no Erlang code is that the language’s syntax is too weird, too hard to read and write, etc. Is the syntax different? Yes. Is it weird or difficult? No, not at all — in fact, it’s actually very simple and regular when compared to popular general-purpose imperative languages. Spend a day or two writing some real Erlang code, and I guarantee you that any initial dislike you might have for its syntax will disappear.

• REST. If you search the blog of any REST proponent, including this one, you’re sure to find all kinds of comments from detractors who argue against REST despite never having used it to develop any real systems. Similarly, the blogs of many WS-* advocates who have never tried using REST contain all kinds of reasons why REST can’t possibly work. Check out the comments in Damien Katz’s recent “REST, I just don’t get it” posting, for example; you have useful ones from those who have obviously used REST and understand its benefits, and then you have other comments that argue against REST while simultaneously showing a great misunderstanding of it. Those detractors would do well to read Bill de hÓra’s excellent response.

Also interesting about these three particular cases is that I don’t personally know of anyone who’s actually tried the approaches and decided against them. In a posting last November, for example, I asked for comments from anyone who had actually tried REST for real and with an open mind, but decided that it was inferior to WS-* and so abandoned it. Either nobody read that posting or no such people exist. I’m fairly confident it’s the latter.

There will always be arguments made by people whose livelihood is somehow threatened by the approach they’re opposing, but I don’t think that’s the source of all the opposing arguments. As developers we can’t possibly try everything, of course, because there just isn’t enough time. It’s inevitable that we’ll sometimes have to resort to researching an approach via only reading, questions and discussion and decide against it without prototyping. But ultimately we developers owe it to ourselves and our employers to keep ourselves objectively informed so that we can take advantage of new approaches whenever appropriate. When a whole bunch of smart developers have success with a particular approach, I don’t see how any responsible developer can actively and vocally oppose it without first objectively trying the approach and experiencing it firsthand.

Eric Newcomer gives us his take on my recent articles (1, 2, 3, 4) and blog postings (1, 2, 3, 4) about RPC, REST, and programming languages:

Anyway, after carefully reading the article and blog entries, I believe Steve is not against RPC per se. He wants people to think before just automatically using it because it’s convenient.

Exactly!

Also spot on are the following postings:

• Bill de hÓra: Patterns of Web Architecture
• Three postings from Stu Charlton:
  • Convenience, Correctness, and Network Interactions
  • Can technology progress?
  • On changing industry mindsets

The beauty common to all these postings is the breadth, depth, and variety of thinking and reasoning they present. There’s a lot to read, but if you’re interested in critical thinking about the design and construction of distributed systems I encourage you to read them all the way through, including the comments, and to follow the links they offer as well.

Stefan Tilkov‘s latest InfoQ article, REST Anti-Patterns, is simply outstanding. It covers all the bases. While it’s a great read for anyone doing RESTful service development, it’s especially suitable for developers who’ve already studied the fundamentals of REST but are still struggling to put them into practice, and also for developers who’ve done a lot of browser-focused web development but not much application-to-application web development.

My latest Internet Computing column, “Convenience Over Correctness,” (PDF) is now available. It continues the exploration of problems with RPC-oriented distributed programming approaches that I’ve been writing about in each of my three prior columns this year, as well as in columns from years gone by and in the erlang-questions mailing list.

For years we’ve known RPC and its descendants to be fundamentally flawed, yet many still willingly use the approach. Why? I believe the reason is simply convenience. Regardless of RPC’s well-understood problems, many developers continue to go down the RPC-oriented path because it conveniently fits the abstractions of the popular general-purpose programming languages they limit themselves to using. Making a function or method call to a remote or distributed function, object, or service appear just like any other function or method call allows such developers to stay within the comfortable confines of their language. Those who choose this approach essentially decide that developer convenience and comfort is more important than dealing with hard distribution issues like latency, concurrency, reliability, scalability, and partial failure.

Is this convenience for the developer the right thing to focus on? I really, really don’t think it is. There are ways of developing robust distributed applications that don’t require code-generation toolkits, piles of special code annotations, or brittle enterprisey frameworks. Perhaps the wonderful programming language renaissance we’re currently experiencing will help us to finally see the light and put tired old broken abstractions like RPC permanently out to pasture.