How to Build a Distributed Messaging System like Discord

Imagine a world where teams of developers, gamers, and online communities come together seamlessly to collaborate, share ideas, and have meaningful conversations. Discord, a popular distributed messaging platform, has made this possible with its versatile and powerful features.

Discord has become a staple for communication and collaboration in the digital age, providing users with text, voice, and video chat capabilities across various platforms. Its applications range from enabling seamless teamwork among software developers to creating a virtual space for gamers to hang out and coordinate their strategies. With its impressive array of features and flexibility, it's no wonder that many are inspired to create their own distributed messaging systems.

Core Components of a Distributed Messaging System

To build a messaging platform like Discord, it's essential to understand its core components:

• Servers and clusters: These provide the infrastructure for users to create and manage their own communities or channels.
• Communication channels and direct messaging: Users can communicate with each other through public or private channels, as well as send direct messages to individuals.
• Message storage and retrieval: A system must be able to store, search, and retrieve messages quickly and efficiently.
• Voice and video communication: For a more interactive experience, voice and video chat capabilities are crucial.
• Notifications and presence indicators: Users need to be informed of new messages and know the online status of their friends or colleagues.

Design Principles to consider while designing a large scale system

• Scalable - If the system works for one user, it would work for millions of users.
• Availability - It would always be available 24x7x365.
• Reliability - It would be reliable, to gain user trust!
• Extensibility - We can add new features without issue.
• Maintainability - It should be easy to maintain.
• Fault Tolerance - It should keep running even if some part fails.
• Others - Security, Performance, Testability.

Technologies and Frameworks

Building a distributed messaging system requires a diverse set of technologies and frameworks:

Backend technologies: Elixir as their core backend language due to its excellent performance, concurrency, and fault-tolerance capabilities, which are crucial for handling millions of concurrent users

Frontend technologies: Discord uses React and React Native for their frontend development because these frameworks provide a highly performant, modular, and maintainable approach to building user interfaces.

Real-time communication protocols: WebSockets, MQTT, and XMPP enable real-time communication between users.

Databases and storage: ScyllaDB as their database solution since it has provided them with a high-performance, scalable, and reliable system capable of handling the demands of millions of users.  ScyllaDB is an open-source, distributed NoSQL database is a drop-in replacement for Apache Cassandra, offering significant improvements in terms of speed and resource efficiency.

Scalability and load balancing: Kubernetes and Apache Cassandra can help distribute the workload and ensure smooth performance.

Designing the System Architecture

The working of Discord

A well-designed system architecture is key to building a reliable and maintainable messaging platform:

• Implementing voice and video communication: Integrating solutions for real-time audio and video chat, such as WebRTC. WebRTC's interoperability, ease of integration, native browser support, peer-to-peer communication capabilities, built-in security, and scalability have allowed Discord to provide a seamless and high-quality communication experience for its users.
• Microservices Architecture: Discord employs a microservices architecture, which breaks down the application into smaller, independent services. This approach allows for better scalability, easier maintenance, and improved fault isolation. As a result, Discord can add new features, optimise existing services, and quickly respond to incidents without affecting the platform's overall functionality.
• Load Balancing: Load balancing plays a crucial role in managing incoming traffic and distributing it evenly across multiple servers. This process helps maintain performance and stability, even when experiencing high traffic volumes. Load balancers ensure that no single server is overwhelmed, reducing the likelihood of bottlenecks and service disruptions.
• Message Queue & Routing: Discord's message queue system is responsible for managing and routing messages between users. It ensures messages are delivered in the correct order and handles message prioritization to prevent bottlenecks or delays. By employing sophisticated routing algorithms, Discord can efficiently deliver messages to millions of users in real-time.
• Gateways & WebSockets: Gateways are the primary means by which Discord communicates with its clients. They utilize WebSockets, a protocol that allows for real-time, bi-directional communication between servers and clients. WebSockets enable Discord to quickly transmit voice, video, and text data while maintaining low latency and high performance.
• Authentication and authorization: Implementing secure methods for user login and controlling access to resources. Discord uses OAuth2 for this purpose. OAuth2 is an industry-standard protocol that allows users to grant applications limited access to their account information without sharing their login credentials.
• Caching: To reduce database load and improve performance, Discord employs caching mechanisms such as in-memory caching and Content Delivery Networks (CDNs). These caches store frequently accessed data, like user avatars, to minimize latency and improve response times.

Conclusion

Building a distributed messaging platform akin to Discord necessitates a thorough comprehension of the fundamental components, technologies, and design principles contributing to its success. In our progressively interconnected world, platforms such as Discord demonstrate the enormous potential of distributed messaging systems in promoting cooperation, community, and communication across diverse sectors and interests. As technology advances, messaging platforms are certain to have an even greater impact on the future of human interaction and collaboration.

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