Elixir & Erlang — CodeTracer

CodeTracer supports Elixir 1.15 and newer, and Erlang/OTP 26 and newer.

The recorder is hosted in the codetracer-beam-recorder repo; ct finds it for you.

How to record an Elixir program

ct run hello.exs

Arguments after the filename are passed through unchanged:

ct run script.exs --count 10

For a Mix project, record the command you would normally run:

ct record -o ./trace mix run -e 'MyApp.main()'
ct replay ./trace

Recording a Phoenix or Plug application

Web applications are recorded as a running server. That has its own guide: Live requests — Elixir & Erlang.

In short:

ct record --server --lang elixir -o ./trace -- mix phx.server

Then ct replay -t ./trace in another terminal shows requests as they arrive.

BEAM processes in a recording

Elixir code tends to spawn many lightweight processes. These are recorded as *threads* within a single recording rather than as separate recordings, so message passing between them stays visible in one place, and you can follow work as it moves from one process to another.