Creating an Elixir DNS Library: Part 1 — Laying the Foundation with the Seeding Mechanism

Introduction

The Domain Name System (DNS) is one of the most critical components of the internet, acting as the phonebook of the web. Every time you type a domain name into your browser, DNS translates that human-readable address into an IP address that your computer can use to access the desired website. Without DNS, navigating the internet would be cumbersome, requiring users to memorize strings of numbers rather than familiar domain names.

In this blog series, I’ll be sharing the journey of building a DNS library from scratch using Elixir — a functional, concurrent, and distributed programming language known for its reliability and performance. The goal is to create a robust DNS resolver that can handle a high volume of queries, ensure data consistency, and remain resilient in the face of system failures.

This first part focuses on the seeding mechanism, which is the backbone of our DNS library. The seeding mechanism initializes and distributes data across the system, ensuring that the resolver can begin processing DNS queries with the correct information.

Understanding the Seeding Mechanism

Before a DNS resolver can begin resolving domain names, it needs to have a set of known values — such as root server addresses and commonly queried domain names — available at its disposal. This process of loading initial data is known as seeding.

The seeding mechanism in our DNS library is designed to:

1. Initialize Data: Load initial DNS records, including root servers and authoritative nameservers.
2. Distribute Data: Ensure that this data is consistently available across multiple nodes in a distributed system.
3. Handle Failures: Implement fail-safe mechanisms to ensure data is seeded correctly even if parts of the system fail.

The overall architecture of the DNS library includes multiple components working in harmony. The seeding mechanism plays a critical role in setting up the system to handle DNS queries effectively.

Let’s take a closer look at the architecture to understand where the seeding mechanism fits in.

Architecture Overview

The architecture of our DNS library is designed with distributed systems in mind. Here’s a high-level overview:

1. DNS Resolver/Recursive Resolver: This component handles incoming DNS queries from users, forwarding them to the appropriate servers to resolve domain names into IP addresses.
2. Root Server: A server that responds to requests for the root of the DNS namespace. It doesn’t store specific domain information but directs the resolver to TLD (Top-Level Domain) servers.
3. TLD Server: These servers manage information about domain names within a specific top-level domain, such as .com or .net.
4. Authoritative Nameserver: This is where the actual DNS records for a domain are stored. It provides the final answer to the DNS query.

In the seeding process, our goal is to populate the DNS resolver with the necessary information about root servers and TLDs so that it can correctly resolve domain names. The seeding mechanism is run centrally, with the ability to distribute this data across multiple nodes, ensuring consistency and availability.

Detailed Look at the Seeding Mechanism

The seeding mechanism begins by loading a predefined set of DNS records — such as the IP addresses of root servers — into the system. This data is then distributed to various nodes in the system to ensure that all parts of the DNS resolver have access to the same information.

1. Centralized Seeder:

• Initialization: The centralized seeder is responsible for loading the initial data. This process is typically run on a single node to avoid data conflicts.
• Scheduling: The seeder is scheduled to run at regular intervals (e.g., every 30 minutes) to ensure that any updates to the seed data are propagated across the system.

2. Data Distribution:

• Replication: Once the seed data is initialized, it is replicated across multiple nodes to ensure that the DNS resolver can function even if some nodes fail.
• Consistency: The seeding mechanism ensures that all replicas of the data remain consistent. Any changes or updates to the seed data are carefully synchronized across nodes.

3. Fail-Safe Mechanism:

• Retry Logic: In a distributed system, failures are inevitable. The seeding mechanism includes a fail-safe mechanism that retries data seeding in case of failure. If a node is down or a replication fails, the system will attempt to reseed the data until consistency is achieved.
• Monitoring: A consistency test mechanism is also implemented to verify that all nodes have the correct seed data. Any discrepancies trigger a reseeding process.

Implementing the Seeding Mechanism in Elixir

Elixir’s concurrency and fault-tolerance features make it an ideal choice for implementing the seeding mechanism. Here’s a high-level overview of how we can implement this in Elixir:

• GenServer for Seeder: The seeding mechanism can be implemented as a GenServer, a process that handles the seeding operation and manages its state.
• Dynamic Supervisor for Distribution: Elixir’s Dynamic Supervisor can be used to dynamically manage the replication of data across nodes. It can spawn processes as needed to handle data distribution.
• Handling Failures with Retry Logic: The retry logic can be implemented using a combination of process monitoring and GenServer callbacks. If a seeding operation fails, the GenServer can attempt to reseed the data after a short delay.

Conclusion and Next Steps

The seeding mechanism is the first step in building a reliable and efficient DNS library in Elixir. By ensuring that the DNS resolver is initialized with the correct data and that this data is consistently available across nodes, we lay a solid foundation for the rest of the system.

In the next part of this series, we’ll dive into distributed data insertion, exploring how we can efficiently insert and manage DNS records across a distributed system. We’ll also look at the challenges of maintaining consistency and reliability in a distributed environment.

Stay tuned as we continue to build this Elixir DNS library, one step at a time!

REPO URL:- https://github.com/Ayoush/ex_dns