When you write Elixir code you quickly discover that the language is built on a runtime called the BEAM. One of the defining strengths of the BEAM is its ability to keep a system running even when parts of it fail. In this article we’ll explore the foundations of fault‑tolerance in Elixir, from the low‑level runtime errors that can crash a process to the high‑level supervision trees that automatically bring those processes back to life.

Why Fault‑Tolerance Matters

Imagine a web‑service that aggregates live sensor data from dozens of IoT devices. The service is

When you first create a process in Elixir you usually think of it as a tiny, isolated unit that can receive a few messages and then terminate. Real‑world systems, however, often need long‑running processes that keep some internal data, react to many different kinds of requests, and possibly communicate with other processes. Those are generic server processes – the backbone of most concurrent applications built on the BEAM.

This article walks you through the evolution from a bare‑bones process that you build yourself to the full‑featured GenServer behaviour that ships with Elixir. Along the way we will: