How Do We Use React Native at Mattermost. Architecture and Design

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Mattermost uses React Native for its mobile app, leveraging the benefits of a single codebase for both iOS and Android. The app's architecture includes TypeScript for type checking, making the code more reliable and easier to maintain. The use of WatermelonDB has provided a scalable solution for state management, particularly for multi-server support and offline functionality. Custom hooks are employed to reduce boilerplate code and manage state effectively. Native features like improved text input and EMM have been integrated to meet specific needs. The app is open-source, welcoming community contributions. Challenges faced include data isolation and offline support, which were addressed with a new architecture.

From Author:

At Mattermost we use React Native for our app. It is a fairly complex project with more than 100.000 lines of code, with plenty of challenges, like performance, reliability or offline support.
This talk will cover some of those challenges and several design decisions we have made so far to address them, along some other decisions to keep the code base readable and navigable.

This talk has been presented at React Day Berlin 2023, check out the latest edition of this React Conference.

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FAQ

Mattermost is an open-source alternative to Slack and Microsoft Teams. It is a chat application with a mobile app written in React Native.

Daniel Espino-Garcia is a software design engineer at Mattermost who gave a talk about using React Native at Mattermost.

You can contact Daniel Espino-Garcia by dropping by the office at the Mattermost community server.

Mattermost uses React Native for its mobile app because it allows for a single codebase that works on both iOS and Android, and it uses JavaScript, which is consistent with the rest of Mattermost's frontend stack.

Mattermost faced challenges such as support for multi-server, data isolation, and offline support. These challenges led to a complete overhaul of the app with a new architecture and interface.

Mattermost initially used Redux for state management but switched to WatermelonDB to handle large states, offline support, and multi-server scalability. WatermelonDB stores the state in a SQL-like database and uses RxJS for reactivity.

Mattermost uses TypeScript for type safety, organizes components functionally, follows specific coding rules and component order, and uses custom hooks to reduce boilerplate and complexity.

Yes, the Mattermost mobile app is open source, and its complete code is available on GitHub.

Mattermost has implemented custom native features such as EMM for session separation, improved text input handling, custom logging, and id-loaded notifications for push notifications to address data residency concerns.

WatermelonDB is a database solution that stores state in a SQL-like database, allowing for scalable state management without loading the entire state into memory. Mattermost chose it for its scalability, offline support, and multi-server capabilities.

Daniel Espino García
Daniel Espino García
18 min
12 Dec, 2023

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Video Transcription

1. Introduction to React Native at Mattermost

Short description:

Today's talk is about how we use React Native at Mattermost. I'll provide disclaimers and explain what Mattermost is. Our React Native app is a chat app with over 100,000 lines of code. We recently overhauled the app with a new architecture, interface, and revised code.

Welcome, everyone. Today I'm here to talk about how do we use React Native at Mattermost. My name is Daniel Espino-Garcia, and I am a software design engineer at Mattermost. If you want to contact me, feel free to drop by the office at Mattermost community server.

First of all, I want to give you some disclaimers about today's talk. What I'm going to talk, is the best solution for any project? No, of course not. Each project is different. Then is there a solution for your project? Depends on your project, but still probably not. My hope is that this talk can spark ideas that you can use in your projects. Is this the best solution for our project? I hope so, but probably not. We are not perfect. We haven't assessed all the possibilities. Every day we learn something new, and every now and then, a new technology appears. This is just what we have tried so far, and worked for us. If you think anything can be improved, please come by the office and let me know. We are always happy to do things better.

With that out of the way, let's start. Here is the agenda for today. So, just to be traditional, let's start with the first point. Why this talk? Let's start explaining what is Mattermost. Maybe just looking at the image you get a good idea of what Mattermost is, but a part of a long definition in our website, we can get a more mundane description. An open source alternative to Slack and Microsoft Teams. This is much more than that, but that gives a broad idea of the basics. And of course, we have a mobile app written in React Native. So, great, Mattermost is a chat app. What makes it interesting to talk about? Well, first of all, the React Native app has a decent size. More than 100,000 lines of code. And so, we have recently done a complete overhaul of the app. The first version was facing some challenges, and we remade the app. New architecture, new interface, and the most of the code, revised and rewritten.

2. React Native Challenges and Benefits

Short description:

We face challenges with multi-server support, data isolation, and offline support. The codebase is open for community contributions. React Native allows writing single code for iOS and Android, and tweaking the app on the native side. It's popular, with an active community. We use React Native because it uses React and fits our stack.

And we believe there's a lot to learn from that. But there are also several challenges that we hope to make the process interesting. One of the biggest ones is support for multi-server. Working with multiple versions, Mattermost is self-managed, but the app is distributed through the stores, so the app must be backwards-compatible. And with multiple servers, the data isolation becomes a huge challenge. You don't want a message meant for a family server and an in-your-works server.

And our big challenge is offline support. People don't expect to receive messages when they're on a plane, but they for sure expect to check the previous messages. And the codebase is open for community contributions, so it is even more important that new eyes are able to understand the code well. Because yes, most of the code is open source and that includes the mobile app! The complete code of the mobile app is in GitHub, so everything I will talk about today is something you can check directly in the code, learn a bit more about it, and even tinker with it, be it in your own fork, or contributing upstream. I hope these are enough reasons to stay on this talk.

Now let's talk about the basis. Here we will cover some general decisions on the project. For example, where are we using React Native? Let me start with what is React Native. You have the official description, but it can be crudely summarized to React Mobile. One of the main advantages, as many other frameworks, is that allows you to write single code that works on iOS and Android. It also allows you to tweak and extend your app on the native side. You need a super-specific native feature for your app? You can dive in the native code and create it. Another important thing is that it's pretty popular, and the community is quite active. Most of your answers are one Google search away. And finally, this will be important later, React Native is written in JavaScript.

And why do we use React Native on Matrimons? Let's see our stack. If we look at the backend, the server code is written in Golang. But on the front side, the browser code is written on React, which uses JavaScript. The desktop app uses Electron and React, that again uses JavaScript. And the mobile app uses React Native, which uses JavaScript. You may see already a pattern. I could talk about alternatives with pure Native or Flutter, but it all boils down to one big reason. Because it uses React. React Native has many other great things that pass up on this.

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