Usdt

Every route in this series goes around the Go runtime: rewrite the source at build time, inject something at process start, or watch from the kernel, because Go gives us no agent API to plug into. This time we ask the runtime what it could hand us. The honest summary for 2026: one long-awaited feature shipped, two open proposals document gaps that have caused real production problems for years, and two experiments of mine are aspirations, not proposals. ...

We’re going to put a probe on one small Go function, twice. First the way OBI (OpenTelemetry eBPF Instrumentation) does it today, then the way a USDT site would. On the way we’ll price a single probe hit, and find that USDT’s pitch is not a discount. This is a companion to the How to Instrument Go Without Changing a Single Line of Code series, between Part 2 and Part 3. The series accompanies my GopherCon UK talk. Part 2 showed what OBI sees. Here we look at how it gets its probes onto Go code, and why USDT keeps coming up. Our function is below. The //go:noinline keeps the compiler from folding it into main, so there is something left to probe. ...

This post expands on the FOSDEM 2026 Go Devroom talk I co-presented with Hannah S. Kim. The talk, demo code, and all benchmark scenarios are available in the fosdem-2026 repository. The Problem Go is one of the best languages for building production backend services. It compiles to native binaries, has excellent concurrency primitives, and produces predictable performance characteristics. But when it comes to auto-instrumentation — adding observability without modifying source code — Go is uniquely difficult. ...