Monolithic Node.js

Are large-scale Node.js systems possible? Empirically, the answer is yes. Walmart and Paypal have both shown that it can be done. The quick criticism is that you need 10X engineers. This a classic, and well-founded criticism. New ways of doing things are often found to be exceptionally productive, precisely because brilliant minds self-select for the new and interesting.

So let’s rephrase the question. Are large-scale Node.js systems possible with mainstream developers? If you believe that these large-scale Node.js systems will resemble the large-scale Java and .Net systems you have known and loved, then the answer is, emphatically, no. JavaScript is far too weak a language to support the complexity inherent in systems of such scale. It’s not exactly type-safe, and half the language is unusable. There’s a reason the best-selling book on the language is called JavaScript, The Good Parts.

Despite this, we’ve managed to build quite a few large-scale systems at my company, nearForm. Here’s what we’ve learned, and how we do it.

The defining attribute of most large-scale, mainstream traditional systems is that they are monolithic. That is, a single large codebase, with many files, thousands of classes, and innumerable configuration files (in XML, if you’re lucky). Trying to build a system like this in JavaScript is indeed the path to madness. The visceral rejection of Node.js that you see from some quarters is often the spidey-sense of an experienced enterprise developer zapping them between the eyes. JavaScript? No! This reaction is entirely justified. Java and .Net have been designed to survive enterprise development. They enable monolithic architecture.

There are of course systems built in Java and .Net that are not monolithic, that are more structured. I’ve built in both styles myself. But it takes effort, and even the best systems fall to technical debt over time. It’s too easy to fall back into the monolithic trap.

Monolithic Systems are Bad

What is so bad about monolithic systems anyway? What does it mean for a system to be “monolithic”? The simplest definition is a system that cannot survive the loss of any of its parts. You pull one part out, and the whole thing fails. Each part is connected to the others, and interdependent on them.

The term monolith means single stone, and is derived from the ancient greek. The ancient city of Petra in modern-day Jordan is one of the best examples of monolithic architecture. Its buildings are constructed in one piece, hewn directly from the cliff face of a rocky mountain. It also provides a perfect example of the failure mode of monolithic systems. In 363AD an earthquake damaged many of the buildings, and the complex system of aqueducts. As these were carved directly into the mountain, they were impossible to repair, and the city fell into terminal decline.

So it goes with monolithic software. Technical debt, the complexity built into the system over time, makes the system impossible to repair or extend at reasonable cost as the environment changes. You end up with things like month-long code freezes in December so that the crucial Christmas shopping season is not affected by unknowable side-effects.

The other effect of monolithic software is more pernicious. It generates software development processes and methodologies. Because the system has so many dependencies, you must be very careful how you let developers change it. A lot of effort must be expended to prevent breakage. Our current approaches, from waterfall to agile, serve simply to enable monolithic systems. They enable us to build bigger and add more complexity. Even unit testing is an enabler. You thought unit testing was the good guy? It’s not. If you do it properly, it just lets you build bigger, not smarter.

Modular Systems are Good

So what are we supposed to do, as software developers, to avoid building monolithic systems. There are no prizes for knowing the answer. Build modular systems! The definition of a modular system is simply the inverse: each part stands alone, and the system is still useful when parts are missing.

Modular software should therefore be composed of components, each, by definition, reusable in many contexts. The idea of reusable software components is one of the Holy Grails of software development.

The greatest modular system humanity has created to date is the intermodal shipping container. This is a steel box that comes in a standard set of sizes, most commonly 8′ wide, 8’6” tall, and 20 or 40 feet long. This standardisation enables huge efficiency in the transport of goods. Each container is re-usable and has a standardised “API”, so to speak.

Sadly, software components are nothing like this. Each must necessarily have it’s own API. There are dependency hierarchies. There are versioning issues. Nonetheless, we persist in trying to build modular systems, because we know it is the only real way to deal with complexity.

There have been some success stories, mostly at the infrastructure level. UNIX pipes, and the UNIX philosophy of small programs that communicate over pipes, works rather well in practice. But it only takes you so far.

Other attempts, such as CORBA, or Microsoft’s OLE, have suffered under their own weight. We’ve grown rather fond of JSON-based REST services in recent years. Anyone who’s been at the mercy of third party APIs, and I’m looking at you, Facebook, will know that this is no promised-land either.

Objects are Hell

The one big idea for modular software that seems to have stuck to the wall, is the object-oriented paradigm.

Objects are supposed to be reusable representations of the world, both abstract and real. The tools of object-oriented development; interfaces, inheritance, polymorphism, dynamic methods, and so on, are supposed to provide us with the power to represent anything we need to build. These tools are supposed to enable us to build objects in a modular reusable way.

The fundamental idea of objects is really quite broken when you think about it. The object approach is to break the world into discrete entities with well-defined properties. This assumes that the world will agree to being broken up in such a way. Anyone who has tried to create an well-designed inheritance hierarchy will be familiar with how this falls apart.

Let’s say we have a Ball class, representing, well, a ball. We then define a BouncingBall, and a RollingBall, both inheriting from the base Ball class, each having suitable extensions of properties and methods. What happens when we need a ball than can both bounce and roll

Admittedly, inheritance is an easy target for criticism, and the solution to this problem is well-understood. Behaviours (bouncing and rolling) are not essential things, and should be composed instead. That this is known does not prevent a great deal of inheritance making it’s way into production systems. So the problem remains.

Objects are really much worse than you think. They are derived from a naïve mathematical view of the world. The idea that there are sets of pure, platonic things, all of which share the same properties and characteristics. On the surface this seems reasonable. Scratch the surface and you find that this idea breaks down in the face of the real world. The real world is messy. It even breaks down in the mathematical world. Does the set of all sets that do not contain themselves contain itself? You tell me.

The ultimate weakness of objects is that they are simply enablers for more monolithic development. Think about it. Objects are grab bags of everything a system needs. You have properties, private and public. You have methods, perhaps overridden above or below. You have state. There are countless systems suffering from the Big Ball of Mud anti-pattern, where a few enormous classes contain most of the tangled logic. There are just too many different kinds of thing that can go into an object.

But objects have one last line of defense. Design patterns! Let’s take a closer look at what design patterns can do for us.

Bad Patterns are Beautiful

In 1783 Count Hans Axel von Fersen commissioned a pocket watch for the then Queen of France, Marie Antoinette. The count was known to have had a rather close relationship with the Queen, and the extravagance of the pocket watch suggests it was very close indeed. The watch was to contain every possible chronometric feature of the day; a stopwatch, an audible chime, a power meter, and a thermometer, among others. The master watchmaker, Abraham-Louis Breguet was tasked with the project. Neither Marie Antoinette, Count Fersen, nor Breguet himself lived to see the watch completed. It was finally finished in 1837, by Breguet’s son. It is one of the most beautiful projects to have been delivered late and over-budget.

It is not for nothing that additional features beyond basic time keeping are known as complications in the jargon of the watchmaker. The watches themselves possess a strange property. The more complex they are, the more intricate, the more monolithic, the more beautiful they are considered. But they are not baroque without purpose. Form must follow function. The complexity is necessary, given their mechanical nature.

We accept this because the watches are singular pieces of artistry. You would find yourself under the guillotine along with Marie Antoinette in short order if you tried to justify contemporary software projects as singular pieces of artistry. And yet, as software developers, we revel in the intricacies we can build. The depth of patterns that we can apply. The architectures we can compose.

The complexity of the Marie Antoinette is seductive. It is self-justifying. Our overly complex software is seductive in the same way. What journeyman programmer has not launched headlong into a grand architecture, obsessed by the aesthetic of their newly imagined design? The intricacy is compounded by the failings of their chosen language and platform.

If you have built systems using one of the major object-oriented languages, you will have experienced this. To build a system of any significant size, you must roll out your Gang-of-Four design patterns. We are all so grateful for this bible that we have forgotten to ask a basic question. Why are design patterns needed at all? Why do you need to know 100+ patterns to use objects safely? This is code smell!

Just because the patterns work, does not mean they are good. We are treating the symptoms, not the disease. There is truth in the old joke that all programming languages end up being incomplete, buggy versions of LISP. That’s pretty much what design patterns are doing for you. This is not an endorsement of functional programming either, or any language structure. They all have similar failings. I’m just having a go at the object-oriented languages because it’s easy!

Just because you can use design patterns in the right way does not mean using design patterns is the right thing to do. There is something fundamentally wrong with languages that need design patterns, and I think I know what it is.

But before we get into that, let’s take a look at a few things that have the right smell. Let’s take a look at the Node.js module system.

Node.js Modules are Sweet

If you’ve built systems in Java or .Net, you’ll have run into the dreaded problem of dependency hell. You’re trying to use component A, which depends on version 1 of component C. But you’re also trying to use component B, which depends on version 2 of component C. You end up stuck in a catch-22, and all of the solutions are a kludge. Other platforms, like Ruby or Google’s new Go language may make it easier to find and install components, but they don’t solve this problem either.

As an accident of history, JavaScript has no built-in module system (at least, not yet). This weakness has turned out to be a hidden strength. Not only has it created the opportunity to experiment with different approaches to defining modules, but it also means that all JavaScript module systems must survive within the constraints of the language. Modules end up being local variables that do not pollute the global namespace. This means that module A can load version 1 of module C, and module B can load version 2 of module C, and everything still works.

The Node Package Manager, npm, provides the infrastructure necessary to use modules in practice. As a result, Node.js projects suffer very little dependency hell. Further, it means that Node.js modules can afford to be small, and have many dependencies. You end up with a large number of small focused modules, rather than a limited set of popular modules. In other platforms, this limited set of popular modules end up being monolithic because they need to be self-sufficient and do as much as possible. Having dependencies would be death.

Modules also naturally tend to have a much lower public API to code ratio. They are far more encapsulated than objects. You can’t as a rule misuse them in the same way objects can be misused. The only real way to extend modules is to compose them into new modules, and that’s a good thing.

The Node.js module system, as implemented by npm, is the closest anybody has come in a long time to a safe mechanism for software re-use. At least half the value of the entire Node.js platform lies in npm. You can see this from the exponential growth rate of the number of modules, and the amount of downloads.

Node.js Patterns are Simple

If you count the number of spirals in the seed pattern at the centre of a sunflower, you’ll always end up with a fibonacci number. This is a famous mathematical number sequence, where the next fibonacci number is equal to the sum of the previous two. You start with 0 and 1, and it continues 1, 2, 3, 5, 8, 13, 21, 34, and so on. The sequence grows quickly, and calculating later fibonacci numbers is CPU intensive due to their size.

There’s a famous blog post attacking Node.js for being a terrible idea. An example is given of a recursive algorithm to calculate fibonacci numbers. As this is particularly CPU intensive, and as Node.js only has one thread, the performance of this fibonacci service is terrible. Many rebuttals and proposed solutions later, it is still the case that Node.js is single-threaded, and CPU intensive work will still kill your server.

If you come from a language that supports threads, this seems like a killer blow. How can you possibly build real systems? The are two things that you do. You delegate concurrency to the operating system, using processes instead of threads. And you avoid CPU intensive tasks in code that needs to respond quickly. Put that work on a queue and handle it asynchronously. This turns out to be more than sufficient in practice.

Threads are notoriously difficult things to get right. Node.js wins by avoiding them altogether. Your code becomes much easier to reason about.

This is the rule for many things in Node, when compared to object-oriented languages. There is simply no need for a great many of the patterns and architectures. There was a discussion recently on the Node.js mailing list about how to implement the singleton pattern in JavaScript. While you can do this in JavaScript using prototypical inheritance, there’s really very little need in practice, because modules tend to look after these things internally. In fact, the best way to achieve the same thing using Node.js is to implement a standalone service that other parts of your system communicate with over the network.

Node.js does require you to learn some new patterns, but they are few in number, and have broad application. The most iconic is the callback pattern, where you provide a function that will be called when the system has more data for you to work with. The signature of this function is always: an error object first, if there was an error. Otherwise the first argument is null. The second argument is always the result data.

The callback function arises naturally from the event handling loop that Node.js uses to dispatch data as it comes in and out of the system. JavaScript, the language, designed for handling user interface events in the browser, turns out to be well-suited to handling data events on the server-side as a result.

The first thing you end up doing with Node.js when you start to use it is to to create callback spaghetti. You end up with massively indented code, with callback within callback. After some practice you quickly learn to structure your code using well-named functions, chaining, and libraries like the async module. In practice, callbacks, while they take some getting used to, do not cause any real problems.

What you do get is a common interface structure for almost all module APIs. This is in stark contrast to the number of different ways you can interact with object-oriented APIs. The learning surface is greatly reduced.

The other great pattern in Node.js is streams. These are baked into the core APIs, and they let you manipulate and transform data easily and succinctly. Data flows are such a common requirement that you will find the stream concept used all over the place. As with callbacks, the basic structure is very simple. You pipe data from one stream to another. You compose data manipulations by building up sets of streams connected by pipes. You can even have duplex streams that can read and write data in both directions. This abstraction leads to very clean code.

Because JavaScript is a semi-functional language, and because it does not provide all the trappings of traditional object-oriented code, you end up with a much smaller set of core patterns. Once you learn them, you can read and understand most of the code you see. It is not uncommon in Node.js projects to review the code of third party modules to gain a greater understanding of how they work. The effort you need to expend to do this is substantially less than for other platforms.

Thinking at the Right Level

Our programming languages should let us think at the right level, the level of the problems we are trying to solve. Most languages fail miserably at this. To use an analogy, we’d like to think in terms of beer, but we end up thinking in terms of the grains that were used to brew the beer.

Our abstractions are at too low a level, or end up being inappropriate. Our languages do not enable us to easily compose their low level elements into things at the right level. The complexity in doing so trips us up, and we end up with broken, leaky abstractions.

Most of the time, when we build things with software, we are trying to model use cases. We are trying to model things that happen in the world. The underlying entities are less important. There is an important data point in the observation that beginning programmers write naïve procedural code, and only later learn to create appropriate data structures. This is telling us something about the human mind. We are able to get things done by using our intelligence to accommodate differences in the entities that make up our world.

A bean-bag chair is still a chair. Every human knows how to sit in one. It has no back, and no legs, but you can still perform the use-case: sitting. If you’ve modeled a chair as a object with well-defined properties, such as assuming it has legs, you fail in cases like these.

We know that the code to send an email should not be tightly coupled to the API of the particular email sending service we are using. And yet if you create an abstract email sending API layer, it inevitably breaks when you change the implementation because you can’t anticipate all the variants needed. It’s much better to be able to say, “send this email, here’s everything I’ve got, you figure it out!”

To build large-scale systems you need to represent this action-oriented way of looking at the world. This is why design patterns fail. They are all about static representations of perfect ontologies. The world does not work like that. Our brains do not work like that.

How does this play out in practice? What are the new “design patterns”? In our client projects, we use two main tools: micro-services, and pattern matching.

Micro-Services Scale

We can use biological cells as an inspiration for building robust scalable systems. Biological cells have a number of interesting properties. They are small and single-purpose. There are many of them. They communicate using messages. Death is expected and natural.

Let’s apply this to our software systems. Instead of building a monolithic 100 000 line codebase, build 100 small services, each 100 lines long. Fred George, (the inventor of programmer anarchy) one of the biggest proponents of this approach, calls these small programs micro-services.

The micro-services approach is a radically different way of building systems. The services each perform a very limited task. This has the nice effect that they are easy to verify. You can eye-ball them. Testing is much less important.

On the human side, it also means that the code is easy to rewrite, even in a different language. If a junior engineer writes a bad implementation, you can throw it away. They can be written in pretty much any language. If you don’t understand the code, you throw it away and rewrite. Micro-services are easy to replace.

Micro-services communicate with each other by sending messages. You can send these messages directly over internal HTTP, or use a message queue for more scale. In fact, the transport mechanism does not matter all that much. From the perspective of the service, it just deals with whatever messages come it’s way. When you’re building services in Node.js, JSON is the most natural formatting choice. It works well for other languages too.

They are easy to scale. They offer a much finer grained level of scaling then simply adding more servers running a single system. You just scale the parts you need. We’ve not found the management of all these processes to be too onerous either. In general you can use monitoring utilities to ensure that the correct number of services stay running.

Death becomes relatively trivial. You’re going to have more than one instance of important services running, and restarts are quick. If something strange happens, just die and restart. In fact, you can make your system incredibly robust if you build preprogrammed death into the services, so that they die and restart randomly over time. This prevents the build up of all sorts of corruption. Micro-services let you behave very badly. Deployments to live systems are easy. Just start replacing a few services to see what happens. Rolling back is trivial – relaunch the old versions.

Micro-services also let you scale humans, both at the individual and team level. Individual brains find micro-services much easier to work with, because the scope of consideration is so small, and there are few side-effects. You can concentrate on the use-case in hand.

Teams also scale. It’s much easier to break up the work into services, and know that there will be few dependencies and blockages between team members. This is really quite liberating when you experience it. No process required. It flows naturally out of the architecture.

Finally, micro-services let you map your use-cases to independent units of software. They allow you to think in terms of what should happen. This let’s you get beyond the conceptual changes that objects impose.

Pattern Matching Rules

Micro-services can bring you a long way, but we’ve found that you need a way to compose them so that they can be reused and customised. We use pattern matching to do this.

This is once more about trying to think at the right level. The messages that flow between services need to find their way to the right service, in the right form, with the right preparation.

The pattern matching does not need to be complex. In fact, the simpler the better. This is all about making systems workable for human minds. We simply test the values of the properties in the message, and if you can match more properties than some other service, you win.

This simple approach makes it very easy to customise behaviour. If you’ve ever had to implement sales tax rules, you’ll know how tricky they can be. You need to take into account the country, perhaps the state, the type of good, the local bylaws. Patterns make this really easy. Start with the general case, and add any special cases as you need them. The messages may or may not contain all the properties. It’s not a problem, because special properties are only relevant for special cases anyway.

Cross-cutting concerns are also easy to support with pattern matching. For example, to log all the message related to saving data, simply grab those as they appear, make the log entry, and then send the message on its way. You can add permissions, caching, multiple databases. All without affecting the underlying services. Of course, some work is needed to layer up the pattern matching the way you need it, but this is straightforward in practice.

The greatest benefit that we have seen is the ability to compose and customise services. Software components are only reusable to the extent that they can be reused. Pattern matching lets you do this in a very decoupled way. Since all you care about is transforming the message in some way, you won’t break lower services so long as your transformations are additive.

A good example here is user registration. You might have a basic registration service that saves the user to a database. But then you’ll want to do things like send out a welcome email, configure their settings, verify their credit card, or any number of project-specific pieces of business logic. You don’t extend user registration by inheriting from a base class. You extend by watching out for user registration messages. There is very little scope for breakage.

Obviously, while these two strategies, micro-services, and pattern matching, can be implemented and used directly, it’s much easier do so in the context of a toolkit. We have, of course, written one for Node.js, called Seneca.

Galileo’s Moons

We’re building our business on the belief that the language tools that we have used to build large systems in the past are insufficient. They do not deliver. The are troublesome and unproductive.

This is not surprising. Many programming languages, and object-oriented ones in particular, are motivated by ideas of mathematical purity. They have rough edges and conceptual black holes, because they were easier to implement that way. JavaScript is to an extent guilty of all this too. But it is a small language, and it does give us the freedom to work around these mistakes. We’re not in the business of inventing new programming languages, so JavaScript will have to do the job. We are in the business of doing things better. Node.js and JavaScript help us do that, because they make it easy to work with micro-services, and pattern matching, our preferred approach to large-scale systems development.

In 1610, the great italian astronomer, Galileo Galilei, published a small pamphlet describing the discoveries he had made with his new telescope. This document, Sidereus Nuncius (the Starry Messenger) changed our view of the world.

Galileo had observed that four stars near the planet Jupiter behaved in a very strange way. They seemed to move in a straight line backwards and forwards across the planet. The only reasonable explanation is that there were moons orbiting Jupiter, and Galileo was observing them side-on. This simple realisation showed that some celestial bodies did not orbit the earth, and ultimately destroyed the Ptolemaic theory, that the sun orbited the earth.

We need to change the way we think about programming. We need to start from the facts of our own mental abilities. The thought patterns we are good at. If we align our programming languages with our abilities, we can build much larger systems. We can keep one step ahead of technical debt, and we can make programming fun again.

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74 Responses to Monolithic Node.js

  1. Dejan Glozic says:

    Hey, Richard. This was a long read but a very rewarding one – thank you for the thought provoking article.


  2. Brian says:

    Though I didn’t track all the points directly, there is another language that provides pretty much all of these things and has been around for a couple decades as well, Perl. CPAN works very similar to npm, though the multi-version thing is still harder, the Perl language does allow for it using `require` rather than `use`. Perl is most often single threaded, and though implementations exist people avoid them. Perl’s lack of OOPness probably has hastened its lack of popularity, but provides the semi-functional world you describe. Message services are easy to write because of the I/O and network handling, and we all know about Perl’s pattern matching capability through regular expressions. Though it isn’t inherent in the language, even the async mechanism is easily implemented using POE (despite its ironic name).

    • Ah, Perl. The first language I got paid to write! 🙂

      The thing about Perl is the code is just unreadable even to yourself after a while. Also, there’s that mega-trend of HTML/CSS/JS taking over the world. So we’re pretty much stuck with JavaScript.

  3. Hi Richard,

    Thanks for the awesome and thought-provoking article (though one might be tempted to describe it as a little… monolithic? 🙂 Had to make the joke; in reality I love long-form stuff).

    On the topic of asynchronous control flow, I’m trying to promote as a way to show people the variety of options for keeping callback-based code clean or choosing a different strategy altogether. If you know of any projects or approaches that should be publicized there, let me know!

  4. MK says:

    Good read, thank you for this.

  5. I’m wondering, wouldn’t your arguments against objects and for modules and service be even more in favor of actor-based systems, Erlang in particular?

  6. I really enjoyed the article — thanks for all the time you put into it.

    I own a (mostly) Rails shop building customer web apps and websites. While you’re focusing on start-ups and enterprise systems here, would a pattern like this be efficient in situations where significant evolution after launching is actually kind of rare (for a number of reasons)?

    • It also helps with the green-field dev – it’s easier to break apart into independent work streams.

      The micro-serices approach also works just fine for Ruby. We have a few ruby processes too.

  7. danny says:

    Thanks for taking the time to write this up! Refreshing to read such a rational post with out hype. You promised no silver bullets and yet make we want to go out and try Node. I think in any environment you work, constant diligence and a very hands-on manager are required to maintain modularity. Since when deadlines come and customers start demanding even the best architecture- be it “micro” or “OO”, start losing their luster.
    I come from the JavaEE world and monolithic is definitely an accurate way to describe our 14 year old system!

  8. Lonny Eachus says:

    Your example of the Ball class, which then has to bounce and roll, is a ridiculously bad example. That doesn’t illustrate any problems with objects. It is simply an example of bad object design.

    I could as easily design a functional program badly, or a procedural program badly. That says nothing about the strengths or weaknesses of those strategies.

  9. @larafale says:

    love reading this kind of stuff.
    really liked your point of view, and willing to ear more 🙂


  10. Intriguing article, with many points on many topics. For now, I have two comments:

    One is that I was surprised that you think OO is motivated by “mathematical purity” or some such. Those of us who promote, say, functional programming, see the attempt to mathematically define and grasp OO (which originated as a scrappy idea from the simulation and GUI worlds, not from programming language research) as complex and even problematic. I don’t see OO as being motivated by mathematics.

    The other surprise is your idea that lack of a standard module system is a good thing. That said, it is definitely astounding that Java after 20 years still does not even have a module system, and that is indeed a real problem (who knows when Jigsaw is coming). JavaScript does let you rig up your own module system if you have first-class closures and everything is dynamic. This is what people did with Scheme and Perl (as one commenter already mentioned as having paved the way toward creating an ecosystem of libraries; I used Perl for quite some time myself before moving on).

  11. You’re still building one giant program out of a bunch of smaller parts; your API just goes over JSON instead of native datastructures. And speaking of which, while you do indeed lose the dependencies between those modules, you lose it because you end up redefining the same data structures (and the code to manipulate them) in a bunch of different modules. Oh, you’re using one module to do that, and the others all talk to it? Congratulations – that’s a dependency.

    The only advantage I see is that, by using JSON (or something better for this purpose, like protobuf or Apache Thrift), you’re more able to gradually rewrite your codebase in another language. But having a whole series of languages, each using their own style and libraries and whatever? That’s a maintenance nightmare!

    • The trick is to write very small services.

      Let’s say a junior developer writes a service badly. Or a senior developer!

      Once you figure out the code is bad, you just throw it away – it’s small enough to rewrite.

      With respect to the dependencies, you’ve changed their nature. They are very loosely coupled. The parts have no knowledge of each other. They only understand the structure of JSON messages. If you then use Postel’s law, you really get a big win. You can even run multiple versions of the same service, and do gradual deploys. And no need for facebook-style feature flag hacks.

      • sheepdog says:

        The thing I don’t get is what happens when these microservices need to happen in a particular order. Or what happens when several services need to happen and complete before another service can happen. What thing has the responsibility to coordinate the services? Or have I missed something?

        • You write a coordinating microservice to manage the flow. If you think about it, such a tightly coupled flow represents a single unit of work so far as the rest of the system is concerned.

  12. Jeff says:

    Was the “How are brains works” sentence supposed to be funny or not? I loved the article and appreciate encouraging projects to be based on how our brains work, but that sentence took me out of the flow of the article and left me thinking “Huh?”.

    Thanks for the great work.

  13. CB says:

    I’ve been (somewhat) obsessed with what I think is the same idea, that I could separate services into single JS functions then cast those functions out to x number of remote servers for execution. I’m working on two prototypes of this, both master-worker setups – one asynchronous job manager that sends jobs (data+function in a message) over SSH with no other running server – and one that chunks data between the nodes and the jobs go out over sockets. Voilà, mapreduce. Of course the entire system itself is a single function.

    Would love to see this catch-on, of course a good buzzword for the media is required. Micro-services, that may do. Glad to see this idea is out there.

  14. CP says:

    Exceptional article. I just forwarded it on to the company. Thank you!

  15. terry says:

    Great post.
    “We can use biological cells as an inspiration for building robust scalable systems. Biological cells have a number of interesting properties. They are small and single-purpose. There are many of them. They communicate using messages.”

    It’s interesting that you mention messaging and pattern matching. I’ve been looking at it quite a bit to get my projects more under control.It turns out that a lot of this can be done in C# and Java as well if proper restraint is used.

    In fact, failing to use messaging(or micro-services if you like) and pattern-matching seem to be one of the biggest impedances to reliably building large software systems successfully using OOP.

  16. The intro gives me the feeling that this is going to be a rant about JavaScript and Node, but the rest of the article describes your love to it and the patterns it forces you to use.

    Very interesting and I agree completely that monolithic systems are bad regardless of language.

  17. I am a fan of OO its biggest goal is to containerise complexity, but with any paradym it is frequently abused by allowing complicated look simple allowing extra complexity to be plied on top to make things get even more complicated.
    It is interesting there are may sexy things coming out of C++11 but many of them make the scope of complexity even greater. Such that if you look at the C++ coding standards of Google or the F35 fighter plane program, features such as exceptions and RTTI are banned or discouraged.
    Design patterns like the word Parlez in the Pirates of the Caribbean are more guidelines rather than the law, however patterns such as MVC if done correctly and consistently, provide great benefits.
    I am a great fan of interfaces and polymorphism, again if done badly then it is crap, but done properly is one of the most powerful features in hiding complexity and functionallity between modules.
    Javascript is a wonderful language I code as much in that as I do in C++, some of its accidental foibles such as closures are now very powerful parts of the language, which again are equivelant to function pointers, functors or delegates in other languages. However it is very weak on things such as proper type support, that is why Typescript and Dart are being strongly pushed by the likes of Microsoft and Google.
    I belive that there is a place for everything, I guarantee in 30 years from now people will be cursing ancient Node.js projects as they lacked the structure and documentation that is back in vogue. Every generation will curse the previous generation and in turn be cursed by the next. I fully applaud the micro services paradym that you suggest, we did this 10 years ago using ActiveX and MTS (HTTP was not that popular in those days) it provides distributed robustness and scalability, but then as now was not the fastest thing on the block for our trading systems and so we went back to monolithic again.

    • John Lindal says:

      You raise a good point. The networking overhead of using lots of micro-services can really kill performance, if you’re not careful.

  18. Geotti says:

    Just as a side-note:
    you can avoid dependency hell in Java by using OSGi, which lets you use different versions of the respective dependencies for each module.
    This doesn’t solve the problem, but when dependencies are under foreign control, there’s little you can do about that other than packaging each of them separately.

  19. If you look into the Gang-of-Four Book, you will find a few design patters which introduce an interface with one single method. If you want to apply this pattern you will usually find yourself writing a whole new class for every single function and often this class is only used once.

    In a language where you are able to write anonymous functions / clojures / lambdas / procs / blocks, whatever you want to call it you don’t need that overhead of writing a new class for each method.

  20. sweptawayhat says:

    That is really bullshit. Next seer on the street with madness in his eyes saying what is wrong. So You are saying: loose coupling, reusability, single reponsibility and messaging… wow that is really new and not known to OOP 😀

    • The thing is how do you get people to actually do all these things? Anything that requires willpower and discipline fails most of the time – we need to find ways to make good structure happen naturally.

  21. pradeep says:

    I like the post, specially the micro service thing

  22. Abhishek says:

    I would like to see how vertx stacks up to this?

    vertx you must be aware is for nodejs on JVM. I know it’s small at its core. So that’s one tick. I know it also goes for the module structure, but I believe that’s more critical and that’s what you want anybody to take away from here in this article, correct?

    Also, there has been numerous critics of node using one core only, no threads whatever, that’s debatable. I am going into larger picture now. How you take this into more cores now?

    Then there is a discussion of the OSGi also thrown in between. Modules and dependency check again.

    Nonetheless, a good thought provoking article. Very powerful concepts.

  23. Tom says:

    Good points. I do find it humorous when developers try to explain this situation. It has nothing to do with programming. If you hear the word “enterprise” it has to do with business decisions. Decisions that create bad software. Follow the money. We all do things we wish we hadn’t =)

  24. Yagiz Erkan says:

    Hi Richard,

    Thank you for this great post. It is certainly thought-provoking.

    What is your experience regarding the network overhead that those very fine-grained micro services impose on the architecture?

    Also, are you familiar with JavaSpaces? You could probably achieve a similar “micro-service” architecture with a tool like GigaSpaces.

    • For very high load applications we use Kafka communicating with the processes via zeromq. We’ve not seen any significant issues with this.

      A traditional multi-tier architecture with many sublevels of HTTP requests will not scale to any great depth, but it can get you surprisingly far before you have to move to a message bus.

      Also, many processes only operate intermittently, nor is this a peer-to-peer approach, so the network load does not become pathological too quickly.

  25. Good points. i’am the author of SwarmEsb, take a look if you are interested in writing complex,modular systems.

  26. Really thought provoking. Thanks for the read!

  27. alex lerner says:

    Richard, you had started off with “Here’s what we’ve learned, and how we do it” — but then went off into the woods with analogies. So, how do you do it? “Are large-scale Node.js systems possible with mainstream developers?” — i dont know, are they? I had spent about 4 months with javascript and node — tutorials, articles, sample code, etc. I am no expert by any means, but from what i had seen, my question is “why jump through all these hoops?” The established technologies, such as ASP.NET or Java, are capable of so much more — and they had been proven over the years. Node is slick and cool — and for a small startup company with low message rates, perhaps it suffices. Even if Walmart and PayPal teams had been able to pull this off, is that really a “typical” development experience or is it more of a “we did it despite it being done in Node” thing? Somehow, serious Node projects feel like a point of crazy pride — something along the lines of “we worked 16 hour days the entire summer without air conditioning, and it was great”. Thats terrific, but i am more concerned with having a “predictible” design, predictible implentation and predictible result — and i am too old to work without air-conditioning. Just like Java in its marketing day, every new technology that comes along promises to be all things to all people — till its not. Why not be mature about it and select a proper tool for the right job? ANyway, i am going on a rant myself here. I liked your article, i wish you had answered your own questions. thanks

    • I’ve been feeling a little guilty about the lack of real code to back to this up (obviously we can’t use existing client code).

      I’m planning a demonstration project. It’s only fair 🙂

  28. Garth says:

    Dumb. Just dumb.

  29. Gerhard Lazu says:

    The concepts which you describe are at least a decade old, a lot of good literature exists on GOOS, DCI, BCE and SOLID. Simple, cohesive code will always be just that, regardless whether you write it in awk or node.js, whether you “package” it in a micro-service or a class.

    As everything is a trade-off, the one that your article is proposing is increased message latency and infrastructure complexity for reduced code complexity and better scaling. The complexity which you’re describing is inherent, you’re just moving it from the code layer into the infrastructure layer.

    Monoliths are bad, I’m all for it, but there is a middle ground between a single monolith and thousands of small micro-services. Trust your common sense and instincts, do the right thing (yes, it’s the choice that involves more effort) and look into the history of software engineering. Believe me that all these problems have been solved in the past, we’re just missing the connections.

    • The problem that has yet to be solved is how to get programmers to code in this way consistently. The nice thing about this approach is that these properties are emergent, without heavy process.

  30. Andrew Vijay says:

    Thanks a lot for this article, I’m editing nearly 60 % of my slides that I’m presenting to my manager and architect guy based on excerpts from this great article. We exactly face a similar situation with a 900MB code base fully in java. Its so hectic and building, restarting and deploying takes all of our souls out. I’m sure I’m gonna get a kudo for this 🙂

  31. Fred Bakker says:

    Interesting insight that most of current programming platforms and paradigmas do not match with how humans think. But i am afraid the microservices paradigma is no match either. Although the human brain can be fairly good modeled as a system of microservices, humans mainly think procedural. First this, then that, if so then do something else. Humans don’t think in messages flows between (micro)services, just as they don’t think functional. Mathematicians think that way, and as we all know, mathematicians are not real humans 😉

    • Yeah you got me there – I am a mathematician by training 🙂

      In practice you do need someone with a good overview of the entire system and how it fits together. But don’t you need that for any software project?

      Micro-services do reduce the cognitive load on junior devs, and the effect they can have on the reset of the system. Go ahead, use global variables! You’re only hurting yourself, not the system.

      • Lennie says:

        Sounds to me like a lot of the issues mentioned like overview and flow can be handled with adding good logging, tooling and statistics/graphing.

        An example of good tooling would be a webinterface which displays an overview what has been deployed and which parts talk to which parts.

        Other simpler tooling people using is what you see people use for for deployment of Docker containers like fig (Docker compose). Where you have a description which have ‘links’ to describe the relationships to make the system connect different services/containers together.

  32. Leon says:

    Hi Richard,
    I have a question here. Suppose we have a system made up of 10 micro-services, then when the system is running on just one machine, are there 10 processes running while each process is the instance of the 10 micro-services ?

  33. Leon says:

    In my opinion, one micro-service will cost one process in the example above(Suppose we have a system made up of 10 micro-services, then when the system is running on just one machine), am I right?

    Thanks a lot.

  34. David Clements says:

    wow, thought provoking.


    1) debugging? some kind of catch all pattern matcher?

    2) adapting paradigm/library to fat client js app – web workers? (possibly too restrictive), iframes? (too heavy). Some kind of abstraction, but that would bring us to modules and the observer/mediator/pubsub pattern. Maybe its not needed in a client app

  35. Cormac Mulhall says:

    “Although the human brain can be fairly good modeled as a system of microservices, humans mainly think procedural.”

    I’m going to have a bit of a rant now 🙂

    Humans don’t think procedural. Programmers think procedural. And that is a huge problem for software development because procedural doesn’t scale, or at least it is too hard for humans to scale procedural precisely because we don’t think like this.

    The problem was never object orientated development, the problem was programmers trained to think like a computer getting their hands on mass on the ideas of OO and fundamentally mis-understanding them because how a CPU works was never relevant to OO design.

    Programmers think “how can I get a computer to do this”. But people in the real world don’t think like this. They delegate naturally. They message pass naturally. They don’t worry about how something will be done, just that it will be done. Programmers think they get this, but often (way too often) they don’t. They still revert back to the fundamental “what is the CPU doing right now”.

    Humans also don’t care how accurate the result is if it is good enough. They view solutions to problems as groups of people/actors working together to solve an issue. How do I get my milk. Well cow makes the milk, the farmer milks the cow, the dairy processes it, the supermarket packages it, I buy it. All those elements happen independently to each other, and no single instruction list is being passed around from cow to farmer to dairy. What is being passed around is messages.

    The reason we look at modern software and say OO hasn’t worked is because modern software is not OO. Alan Kay once lamented that he wished he had called it message orientated programming because messages are the big idea, not objects. Kay was coming from a biology background, he viewed object orientated systems like cells in an organism, all working together but without any single control list or “program” being run. He has famously said that the only actual object orientated system in existence is the Internet, and that the object revolution hasn’t happened yet. Think about that, billions of lines of code in OO languages and the inventor of the concept is saying that none of this is OO.

    Basically programmers ruined OO design because they missed the big idea and just used OO as a new way to structure their data structures and COBAL programs (as David West likes to say, mostly to get a rise out of the audience)

    Micro-services are a re-discovering of the original principles of object orientated design, OO taken to the level of the network, rather than the CPU.

    And they will probably be the way that OO finally gets accepted/understood by most programmers because you simply cannot bring it back to the procedural level. By definition you cannot reduce a group of micro-services down to the level programmers like of “what is the CPU doing right now and what will it do next”

    Rant over 😛

    Excellent article, Richard, micro-services are the future. The only thing I would dispute is that Objects are not hell. Modern perversions of objects (C++, Java etc) are hell because they don’t understand objects.

  36. Eric Douglas says:

    Awesome article! Many thanks for that!

    I felt that I’ve evolved years in minutes…

  37. Stefan Houtzager says:

    Agreed with a lot, entertaining read. I heard it all before, but this is a very nice story bringing things together in a different way. I appreciate the links to some old histories especially. A nicely spiced meal, for free, thanks! What I miss most is a more critical view on node.js. I think javascript is not the best language for it’s goals. Node.js creator Ryan Dahl in an interview:
    ” Why did you originally choose javascript for node?

    Dahl: Originally I didn’t. I had several failed private projects doing
    the same on C, Lua, and Haskell. Haskell is pretty ideal but I’m not
    smart enough to hack the GHC.”
    Look at yesod, written in haskell: “Instead of dealing with callbacks, you get to write normal code. By utilizing light-weight green threads and event-based system calls, your code automatically becomes non-blocking, without the pain.”
    Look at phoenix, written in elixir (google for it).
    Entertaining movie:
    From a node developer that left:

  38. Great article, thank you.

  39. Yaseen says:

    Great article thanks.
    The comments and their replies pretty much complement the article and there’s little else I can think of adding.

    having spent many years doing enterprise architecture and development I myself come from a Java EE monolithic background and have recently embraced the world of Javascript (which incidentally I used to reject due to all the known issues) an Node.

    My question is how do you see the new changes in ES6 and Typescript in particular that’s trying to bring JS to an OO fold? Would the Node ecosystem not begin to suffer from the same ailments that you mention in the article?

  40. Yaseen says:

    I take my comment back due to the fact that I disagree with lots of what you say and I don’t think you can benefit my knowledge in any way, shape or form – pff!

  41. CCPony says:

    Well, I THINK that you meant to write:

    Instead of building a monolithic 100 000 line codebase, build 1000 small services, each 100 lines long.

    * laughing * Sorry. I couldn’t resist. But it DOES raise the questions as to how many microservices are TOO many. It’s not hard to imagine an enterprise application with 10’s of thousands of microservices. At what point is performance badly impaired?

  42. Stefan Houtzager says:

    Couple more critical links about node.js:
    Some comments from

    rdtsc 217 days ago [-]

    I wouldn’t use it.
    1) Bad concurrency model — callbacks, promises and futures are in general inferior abstraction model compared to green threads, actors, regular threads. Performance-wise it might do well in some scenarios but you are forced to use a more complicated abstraction to get that performance It is not worth it. In general it is appealing because it looks simple in small demos, as applications grow it becomes a mess.
    2) npm modules are easy to use and that’s great. Good model (well maybe except for deep nesting which breaks based on max path in say Windows, but I hear they are fixing that). The problems I found was that a lot of modules were of low quality. Code half-finished, buggy, developer moved on to something else, etc. Somehow it seems more so than say in the Python community.
    3) Javascript is not the best language. There is a reason there is a “Javascript: The Good Parts” book. Because there are lot of crazy decisions made in it originally and a lot of bad “parts”. If there was a choice between FORTRAN, Cobol and Javascript. I would pick Javascript hands down, but there are other languages out there today.
    However. If all you know is Javascript and you want to write a small demo, then go for it. It will be the least friction.
    So with all this complaining and whining, how about some constructive stuff. What language / frameworks might be more interesting / better.
    1) Go : good concurrency model, supported by a large community, good performance. Lots of big companies use it.
    2) Elixir : new kid on the block, fun, one of the friendliest communities. Probably best concurrency model — actors. It uses Erlang’s VM, so that part is rock solid, battle tested for many years. But not as many libraries. But can use existing Erlang libraries from it. Also best for reliability and fault-tolerance.
    3) Python : easy to learn, lots of libraries, lots of material how to use it. This is my go-to language to get stuff done quickly. Try Python 3 if you start from scratch.
    4) Clojure, Scala, Java: run on JVM. Battle tested, probably lots of libraries. Personally not as familiar with it, most enterprise and big sites out there run on the JVM currently.

    Tloewald 217 days ago [-]

    If you want to level constructive criticism, then set aside language prejudice. Obviously, if you don’t like javascript, move on.
    It’s great you like Python. Use a Python framework. You can point out Javascript’s warts and we can laugh at the Python 3 migration. (And really, both of these criticisms are out of date. Javascript is _fine_ these days and Python 3 is moving towards backwards compatibility; sure Javascript has warts, but that’s because it’s backwards-compatible. You know, like… never mind.)

    rdtsc 217 days ago [-]

    > Obviously, if you don’t like javascript, move on.
    I don’t like many things and like other things. All in various degrees. So I shared my experience.
    But you seem to be interested in what I like, so I’ll share more. I would say, in general I am not really a “$X language” developer. A lot of people say “Oh, I am a Java developer” or “A Node developers”. I am not a Python developer, or Erlang developer. I am a developer who solves problems. And languages are tools ( so far I used Javascript in the past, as well as Erlang, Java, C++, C#, and yes, even FORTRAN ).
    The point about Python was that currently, most tasks I had to do, were made quicker and easier by using Python. Some are solved better by Erlang, some by C#.
    Javascript and Node I found had enough negatives so it seemed helpful to share that too.
    > Obviously, if you don’t like javascript, move on.
    I didn’t know this was Javascript land and I wasn’t allowed to come in without proper credentials. (See note about “friendly community” regarding Elixir in my original post, that wasn’t by accident. I didn’t want to say anything more about Node community, but I will now — yeah it is not the friendliest, lost of insecurity and angst in it, which was another turnoff to me personally).

  43. Bernard says:

    I am currently working on modularizing a monolithic system as microservices. This is one of the best articles I could find on the web! I would like to know how production ready is Seneca at the moment?

    Thanks, Joe.

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