Building a modular monolith with Fastify

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In my journey through Nodeland, I saw most teams struggling with the free-form nature of Node.js development: there are no guardrails for maximum flexibility. Yet, not all paths offer a smooth ride.
How to build applications that are well-organized, testable, and extendable? How could we build a codebase that would stand the test of time?
In this talk, we will explore how to avoid the trap of Singletons to create robust Node.js applications through the use of Fastify plugins: we will build a modular monolith!

This talk has been presented at Node Congress 2023, check out the latest edition of this JavaScript Conference.

FAQ

Fastify is a web framework for Node.js designed for building web applications, backends, and APIs efficiently. It offers built-in features like a logger named Pino and supports creating routes using AsyncAwait. Fastify is recommended for its ease of use and performance benefits in Node.js environments.

Fastify's encapsulation allows developers to create context within contexts, ensuring that each layer of the application does not share state with the previous one. This feature aids in structuring applications into segmented plugins, enhancing code maintainability and scalability.

To harness Fastify effectively, ensure you define schemas for both incoming and outgoing data. This not only secures your application but also optimizes JSON handling. Additionally, use the 'under-pressure' module to protect your service from becoming overloaded.

The main disadvantage of using MVC systems is that they often do not scale well in terms of complexity. As applications grow, maintaining a large number of models and controllers can become cumbersome and lead to spaghetti code, making the system difficult to manage.

You can follow Matteo Collina on Twitter at @MatteoCollina, subscribe to his newsletter for updates in the UK, or watch his streams on Twitch where he shares insights on software development and more.

Instead of MVC, applications should be structured by domains or features, segmenting distinct functionalities and communicating over well-defined APIs. This approach helps in managing complexity and maintaining clear boundaries between different parts of the application.

Matteo Collina
Matteo Collina
30 min
14 Apr, 2023

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  • Sreeharsha Raveendra
    Sreeharsha Raveendra
    I don't know if my brain travels as fast as Matteo, man was sprinting in his mind
Video Summary and Transcription
Fastify is a powerful tool for building web applications and APIs in Node.js, with millions of downloads per month. It promotes encapsulation and structuring through plugins and decorators, allowing for code and data segmentation. The talk emphasizes the importance of modularizing applications by domains and features, and showcases a demo of a typical Fastify application. The speaker also discusses the benefits of using Platformattic for refactoring and launching Fastify applications in the cloud. The Q&A section covers topics such as dependency injection and debugging, while also highlighting the importance of separating business logic from API contracts.

1. Introduction to Fastify

Short description:

Happy to be here at Node Congress. Talking about Fastify, a powerful tool for building web applications and APIs in Node.js. It has a built-in logger called Pino. Fastify is widely used with millions of downloads per month. The problem with using a model view controller system is that it doesn't scale well in complexity. Instead of building a view layer, we focus on building APIs. This can lead to a large number of models and a lengthy routes.js file.

So, happy to be to be here at Node Congress. I have been... Look, I've known about this conference for a while, and it's so great to finally be here in Berlin. It's been a long time since I came to Berlin, and I kind of missed it. So, look, I am here talking about Fastify. So, it's great to be here, and so on.

So, a couple of things about me. I have a newsletter too, and in the UK, if you don't matter, just subscribe there, or follow me on Twitter, at Matteo Collina. And I also am also streaming on Twitch, so if you like that, you can join. Also, I need to correct Liz, because since I put in the bio, it's actually 17 billion in 2022. Whatever. Like, it's so much fun.

So, okay. So, today, we are talking about Fastify. And if you don't know Fastify, you probably should, but you should probably use it if you're using Node.js, right? This is not Congress, so I don't know. You should probably use Fastify to build your web applications and backends and APIs. How do you use it? Very easy, you require import whatever. It has a logger built in. EpiDays, you want a logger in your application, right? It's called Pino. And you can use it to create your routes using AsyncAwait and all the other shenanigans that you might want. It's probably 4 billion million times per year or something, downloads per month.

So, okay. Let's talk a little bit about why you should not use Fastify or anything, or how to not use Node.js. How many of you have built a model view controller system in your career? Great. What's the problem with this system is that ultimately it doesn't scale. In what sense it doesn't scale? Well, it doesn't scale well in complexity. If you are building an application, and you're building it using following model view controllers, okay, let's start with the view. Most of the time there's no view layer anymore, we just do build API, so that's gone. So if you are writing a piece of code, it either goes into the controller or the models, and if it, you know, a 50% chance. After a bit of time you have 2000 models and a routes.js file that is 10,000 lines long.

2. Building Monoliths with Fastify

Short description:

Truth. MVC leads to Carbonara and spaghetti code. Instead, structure your application by domains and features. Avoid mixing features' databases. Fastify offers encapsulation through plugins, enabling code and data segmentation. It has no cost or overhead and supports decorators. Encapsulation allows for nested contexts without sharing data between layers.

Truth. This is actual number from real code. So it doesn't really work well in that way, and it doesn't scale well in complexity. What do you do instead? Because the question is, if model view controller is not good enough, what do you do instead? And how a lot of few major companies and a few major system can actually build monoliths, because model view controller is not good but they still ship monoliths. So there's a few article every now and then about monoliths around, and why and how, what they are doing.

Well, to be honest MVC leads to Carbonara and spaghetti code, but I like the Carbonara and not the spaghetti code. That's it. So how do you do it? You need to structure your application by domains, by feature. You need to identify what are the key features of your application and segment it. And in between those systems, you tend to communicate over well-known APIs. The important part is, do not have one set of features, read the database of the other set of features. Because the moment you start dipping into both, then you have a lot of, you don't know how you end up with your relations. Or another term to say is if in order to fetch a data, you need to do a 10, you need to join 10 tables, you probably have the wrong schema. Okay? So think about that and what you're doing and reflect on your life choices.

So what makes a domain and how do we build monolith? Like it is something that we want to do, right? It's a good thing. And well, you know, it typically, it's a specific subject that is being developed, okay? Typical cases is the catalog or the order management system or a cart or whatever you want to call it, okay? In some of the stuff that they're recently been developing, it's called, we have a domain which is the organization and the teams and other stuff is about the applications and the code that you run on our cloud. So anyway, it's domains, and you want to avoid the spaghetti code. So what does Fastify as for helping out building with this stuff? Fastify offers a concept called encapsulation. So it enables you to structure your application in a set of plugins that you can use to segment your data, to segment your code and in that way they don't share anything, essentially. Now a few few may ask but you could do this before, right? There's other techniques. Yes, but this has no cost has no overhead whatsoever. Okay, it's super fast, so you don't have anything to pay for it. And it's great. It has also concept of this called the decorator. So you can actually add stuff to your to your code and application. So how does encapsulation work? You basically can create context within context within context within this context, like kind of from a big matrioshka, and each layer does not share anything with the previous one. It's great. It's something disappeared. Okay, fun. Some missing.

QnA

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