RESTful is hardly harmful.

A provocative essay came up on Hacker News today, entitled RESTful considered harmful.

The summary of the essay:

  • JSON is bloated in comparison to protobufs and similar binary protocols
  • There are no interface contracts or data schema
  • HATEOAS doesn’t work
  • No direct support for batching, paging, sorting, etc – eg no SQL semantics
  • CRUD is too limited
  • No, really, CRUD is too limited
  • HTTP Status codes don’t naturally map to business semantics
  • there’s no queueing, or asynchrony
  • There are no standards
  • Backward compatibility is hard

Let’s have a look at the validity of these concerns.

1. JSON is bloated in comparison to protobufs

The essay cites “one tremendous advantage of JSON”: human readability, and then completely discounts this advantage by saying that it’s bloated. It really is a tremendous advantage, which is why XML won over MQ’s binary protocol and the XDR from Sun RPC, and the NDR from DCE RPC, and every other frigging binary protocol. And readability is why JSON displaced XML.

Ask yourself this: what is the value of readability versus the performance advantages of the alternatives, like Thrift or protobufs? Is readability worth 1x as much as the improved efficiency you might get with protobufs? 2x? I believe that for many people, its worth 100x. It trumps all other. For uber-experts, it’s deceptively attractive to wave away the advantage of human-readability. For the rest of the world, for 97% of developers, it’s a huge, Huge, HUGE advantage. For high speed financial trades, JSON is wrong. For Google’s internal interfaces, wrong. For most of the world, RIGHT.

AND as the essay notes, REST doesn’t prescribe JSON. Or XML. Or anything. There’s a content-type header, and clients and servers can negotiate it. If the client says Accept: application/x-protobuf, and the server can send it, bliss for you. So this point – “JSON is bloated” – is not only not valid (false) in the first place, it’s also not an argument against REST.

2. There are no interface contracts or data schema

This is a feature. OMG, have we not tried this enough times? Did this guy skip his “History of IDL compilers” course in the Computer History department at school? Sun RPC IDL. DCE RPC IDL. Corba IDL. WSDL, ferpeetsake! XML Schema!!

It’s pretty straightforward to deliver plain-old-XML over HTTP, which is quite RESTful. More popular is JSON-over-HTTP. Either of those have schema languages. Few people embrace them, though. Why? Because IDLs and Schema languages are too much structure, and they handcuff people more than help them. We have fortunately learned from the past. There are more tools coming in this area, for those who wish to embrace them. See apistudio.io .

3. HATEOAS doesn’t work

Mmmmm, yep. No argument here. In my experience, nobody really uses this, in practice. Pragmatic REST is what people do, and it generally does not use HATEOAS.

4. no SQL semantics

Uhhuh, true. This has been addressed with things like OData. If you want SQL Semantics, seek solutions, don’t just complain.

5. CRUD is too limited

Really? This is a problem? That you might need a switch statement in your code to handle different types of events? Really?

6. CRUD is really too limited

….

Mmmmm, sorry. I have to stop now. I’m completely bored of responding to this essay by now. Except for one more:

10. Backward compatibility is hard

This has NOTHING to do with REST. This is just true. Back compat in any interface is tricky.


In summary, I don’t find any of the arguments compelling.

Let me draw an analogy. The position in this essay is like saying “Oil is no good as a transportation fuel.” Now, Oil has it’s drawbacks! Oil is dirty. We can imagine alternatives that are better in theory. Even today, in specific local situations (daily use, short trips, urban travel) electric cars are better, MUCH better, than fossil-fuel based cars. (An bicycles are even better than electric cars) But gasoline-powered cars deliver massive utility to billions of people. Gasoline refueling stations are everywhere. The delivery system for gasoline is mature and redundant. The World RUNS, very effectively, on gasoline-powered transport, by and large. Objectively, Oil is VERY GOOD as a transportation fuel.

Sure, we’ll evolve better approaches in the future. That’s great. And sure, we can imagine a world with electric-powered vehicles. But today, in the world of reality, Oil wins.

And likewise Pragmatic REST, HTTP, JSON, and schema-less interfaces are winning. We’ll evolve better approaches. But today, This platform wins.

HTTP, HTML, Javascript, and JSON are ubiquitous, are the foundation of the web, and are not going anywhere. Any architect is free to choose other options, and they might have good reasons for doing so. On the other hand the vast majority of installations won’t benefit from using protobufs or thrift, or some non-HTTP protocol. Pragmatic REST, JSON and HTTP are very very safe choices in the vast majority of scenarios.

Cheers

I don’t see the point in Revoking or Blacklisting JWT

I heard someone asking today for support for Revocation of JWT, and I thought
about it a little, and decided I don’t see the point.

Specifically, I don’t see the point of the process described in this post regarding “Blacklisting JWT in express-jwt“. I believe that it’s possible to blacklist JWT. I just don’t see the point.

Let’s take a step back and look at OAuth

For those unaware, JWT refers to JSON Web Token, which is a type of token that can be used in APIs. The format of JWT is self-describing.

Here’s the key problem tokens address: how does a server decide whether to honor or reject a request? It’s a matter of authorization. OAuthV2 has been proposed and is now being used by the industry as the model or framework for enabling authorization in API-oriented apps. Basically it says, “give apps tokens, then grant access based on the token.”

Often the way things work under the OAuth framework is:

  1. an app running on a mobile phone connects to a token dispensary (a server) to request a token
  2. the server requires the client (==app) to provide some credentials before generating and dispensing a token. Sometimes the server also requires user authentication before token delivering a token. (This is done in the Authorization Code grant or the password grant.)
  3. the client app then sends this token to a different server to ask for services.
  4. the API server evaluates the token before granting service. Often this requires contacting the original token dispensary to see if the token is good, and to see if the token should be honored for the particular service being requested.

You can see there are three parties in the game: the app, the token dispensary, and the API server.

One handy optimization is to put the API endpoint behind an OAuth-aware proxy server, like Apigee Edge. (Disclaimer: I work for Apigee). The app then contacts Edge for a token (via POST /token). If the credentials are good, Edge generates and stores an opaque token, which looks like n06ztxcf2bRpN42cDwVUNvroGOO6tMdt, and delivers it back to the app. The app then requests service (via GET /service, or whatever), passing the previously obtained token. Edge sees this request, extracts the token within it, evaluates whether the token is good, and either passes the request through to the API endpoint or rejects it based on the token status.

The key thing: these tokens are opaque. The app doesn’t know what that token is, beyond a string of characters. The app cannot tell what the token is good for, unless it asks the token dispensary, which is the final arbiter. Sometimes when dispensing the token, the token dispensary also delivers metadata about the token, like: expiry, scopes, and other attributes. But that is not required, and not always done. So, bearer tokens are often opaque, and they are opaque by default in Apigee Edge.

And by “Bearer”, we mean… an app that possesses a token is presumed to “own” the token, and should be granted service based on that token alone. In other words, the token is a secret. It’s like cash money – if you lose it, someone else can spend it. But not exactly like cash. An opaque token is more like a promissory note or an IOU; to determine if it’s worth anything you need to go back to the issuing party, to ask “are you willing to pay up on this note?”

How is JWT different?

JWT is a different kind of OAuth token. OAuth is just a framework, and does not stipulate exactly the kind of token that needs to be generated and delivered. One type of token is the opaque bearer kind. JWT is an alternative format. Rather than being an opaque string, JWT is a self-describing format for bearer tokens. Generally, a JWT includes an encoded payload that can be decoded and read by anyone, and that payload contains a bunch of claims. The standard set of claims includes: when the token was generated (“issued at”), who generated it (the “issuer”), the intended audience, the expiry, and other things. JWT can include custom claims, such as “the user is a good person”. But more often the custom claim is: “this user is authorized to invoke /serviceA at endpoint http://example.com”, although this kind of claim is shortened quite a bit and is encoded in JSON, rather than in English.

Optionally accompanying that payload with its claims is a signature, which can be verified by any party possessing the public key used to sign it, (or, when using secret key encryption, the secret key). This is what is meant by “self describing”. The self-describing nature of JWT is the opposite of opaque. [JWT can be unsigned, can be signed, or can be encrypted. The encryption part is an optional part of the spec.]

(Commercial message: I said above that Apigee Edge generates opaque bearer tokens by default. You can also configure Apigee Edge to generate signed JWT.)

Why Self-describing Tokens?

The main benefit of a model that uses self-describing tokens is that the API endpoint need not contact the token dispensary in order to determine if the token is good, not-expired, and if a request bearing such a token ought to be honored. In other words, JWT supports federation. One party issues the token, another party can verify it, without contacting the issuer. Remember, JWT is a bearer model, which means the possessor of the token is presumed to be authorized to get service based on what’s in the token. This is truly like cash money this time, because … when honoring a JWT, the API endpoint need not contact the issuer, just as when accepting a $20 bill, you don’t have to contact the US Treasury to see if the bill is worth $20.

So how ’bout Revocation of JWT?

This is a long story and I’m finally getting to the point: If you want JWT with powers to revoke the token, then you abandon the federation benefit.

Making the JWT self-descrbing means no honoring party needs to contact the issuer. Just verify the signature (verify the $20 bill is real), and then grant service. If you add in revocation as a requirement, then the honoring party then needs to contact the issuer: “I have $20 bill with serial number T128-DCQ-2872JKDJ; should I honor it?”

It means a synchronous call across the two parties. Which means federation is effectively broken. You abandon the federation benefit.

The corollary to the above is that you also still incur all the overhead of the JWT handling – the signing and verification. So you get all the costs of JWT and none of the benefits.

If revocation of bearer tokens is important to you, you could do the same thing with an opaque bearer token and eliminate all the fussy signature and validation stuff.

When you’re using an API Proxy server like Apigee Edge for both issuing and verifying+validating tokens, then there is no expensive additional remote call to check the revocation status. But you still lack the federation benefit, and you still incur this signing and verification nonsense.

I think when people ask for the ability to handle JWT with revocation, they don’t really understand what they’re asking.

Adopting Microservices means speed

“it’s crucial to adopt a four-tier application architecture in which applications are developed and deployed as sets of microservices.”

I love this article from the nginx.com website, courtesy of Hacker News. Very good overview of the “microservices” meme that is currently rippling through the industry. This is stuff we’ve all known – heck, we’ve been doing SOA for 10+ years – but the new term is helping to organize thoughts and understanding about why services as a metaphor is important, why services need to be lightweight, why service contracts (APIs!) need to be loose and forward-compatible, why the development of cooperating services must be done independently.

“It’s becoming increasingly clear that if you keep using development processes and application architectures that worked just fine ten years ago, you simply can’t move fast enough to capture and hold the interest of mobile users who can choose from an ever-growing number of apps.”

Oh yeah! Preach it!

The article discusses Netflix and their adoption of the microservices architecture.

I really respect Netflix as a company that moves quickly and constantly adjusts, seeking optimized architectures to address business problems. All the talking and proselytizing they’re doing around microservices is just the latest reason to really like them. I also really hate Netflix as my children seem to be unable to resist the service for even 15 minutes. Me and Netflix – It’s complicated.

Independent of Netflix and the microservices topic, nginx is also really cool. I found it super easy to configure to accomplish some nifty things in some of my work.

API-First Development

POP.co logo

Pop.co explains why they went to an API-first development model.

This is going to be a continuing trend. More and more places are already doing this, even if they’re not blogging or talking about it. With the continued growth of mobile devices, to become co-equal with a website, if not the predominant way that people interact with companies, there is an imperative to go to APIs first.

Why?

  • Consistency is key. Companies will want to deliver the same or comparable capabilities, to the extent possible, across websites and mobile apps. There’s obvious duplication. Rather than duplicate efforts, APIs allow companies to reap economies of scale across the two platforms. One API can support both. New features can be released to both simultaneously using the same service-layer infrastructure.
  • Agile is not pure hype. This is how smart software developers work. And APIs are designed for Agile philosophy. APIs get versioned and updated rapidly. There’s no rigid, fixed schema, no “WSDL” to update and fiddle with. Think about it – that is just a clean restatement of the “minimal docs” plank of the Agile philosophy. If you’re agile, you want APIs. They support your work rather than fight it.

Everyone is going to be doing this.

I don’t agree with everything in that POP.co post. For example, POP lists “Scalability” as a reason for going to APIs. I don’t see it. Their theory is that Separation of concerns leads to scalability, meaning they can have web servers and API servers and scale them independently. But Microsoft refuted this as a requirement for high performance long ago. ASPNET proved that you can build a stateless layer of web/app servers, backed by a fast datastore layer, that screams. There’s no real performance benefit to separating the HTML server from the “API Server”.

On the other hand, the other reasons that POP.co offers for going to APIs first, make a ton of sense to me.

APIs within the Enterprise – a Webinar

Recently I did a web chat with colleague Greg Brail discussing the use of APIs in the Enterprise.

Quick summary: SOA has been used with success within enterprises to interconnect systems. APIs address a different set of problems, and there is real value to be gained by using APIs to interconnect systems within the enterprise, as well as to provide external or partner access into enterprise systems.