CLTRACE: DTrace-inspired tracing and observability for Common Lisp

What is CLTRACE?

CLTRACE is a new observability framework for Common Lisp that aims to let developers debug live production systems with minimal interference. It takes explicit inspiration from DTrace — think programmable, on-the-fly probes for Lisp — and is published on GitHub. Warning: the project is labeled ALPHA quality in its README, so it's early days and you should use it at your own risk.

How it works

The system exposes programmable probes you can deploy or create interactively while a program is running. You can register entry probes on functions, apply predicate filters, increment aggregations across probes, and set program-scoped variables for cross-probe use. Want a cheap, running count of calls to a function where argument a equals 3? CLTRACE claims you can do that without tearing your service apart. Short, dynamic, and low-overhead — that’s the pitch.

Status and provenance

Stability is the obvious catch: alpha. The README is blunt about that. It has been reported that the author says LLMs didn’t write a single line of the code, though they were used as reference and for brainstorming — a small, telling note in an age when everyone asks, “Did the bot do it?” Allegedly, the implementation is hand-crafted Lisp and still very much a work in progress.

Why it matters

Observability has been the hot topic for years — eBPF, distributed tracing, metrics galore — yet niche languages often get bespoke, slower-moving tooling. For Lisp shops that still run critical production systems, CLTRACE could be the sharp, lightweight tool they’ve been missing. Will it mature into something production-ready? Time will tell. Meanwhile, curious developers can peek at the repo and kick the tires on the idea: https://github.com/MarceColl/CLTRACE.

Sources: github.com/marcecoll, Lobsters