GenServer the "rabbit hole" — Part 2: The Silent Cascade

Sat, 16 May 2026 14:10:51 -0300

Continuation of GenServer the “rabbit hole”. If you haven’t read it yet, I recommend going there first — we’ll start from the same genserver_study project and the same concepts of mailbox, supervisor and max_restarts.

In the previous article we explored how a “misbehaving” GenServer can shut down the whole supervision tree when it bursts the supervisor’s max_restarts. We showed how messages are lost in the mailbox and how “Let it crash” isn’t exactly a blank check to let processes break randomly.

GenServer — the "rabbit hole"

Sat, 19 Jul 2025 13:36:37 -0300

When we explore Elixir’s strengths as a programming language, two stand out compared to other languages on the market:

🚀 3. Concurrency and Scalability

Uses actors (processes) for concurrency (each with its own memory and message queue).

Millions of processes can run concurrently with low overhead.

Built-in tools for distribution across multiple nodes.

🛠 4. Fault-Tolerance and Supervision Trees

“Let it crash” philosophy: Failures are expected and isolated.

Supervision trees: Automatically restart failing processes, making systems self-healing and resilient.

GenServer is an abstraction over the Erlang VM’s process model, shipped by the language core, that connects directly to Elixir’s concurrency and supervision tree features. Because it’s a common pillar in the architecture of Elixir systems, and because it’s covered “prematurely” in the official docs (Client-server communication, OTP Concurrency), newcomers tend to model their first Elixir solutions using the abstraction provided by the GenServer module. It takes a while before the official doc gets to its first disclaimer for the unaware: When (not) to use a GenServer.

Otp on DanielWS

GenServer the "rabbit hole" — Part 2: The Silent Cascade

GenServer — the "rabbit hole"

🚀 3. Concurrency and Scalability

🛠 4. Fault-Tolerance and Supervision Trees