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Felix Geisendörfer @felixge.de · 06/05/2026

PSA: Green Tea GC in go1.26 is incredible 🚀 This is what we saw for two big Go services. We'll try to gather more data and share it soon.

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Felix Geisendörfer @felixge.de · 31/03/2026

The OpenTelemetry Profiles Signal is now in Alpha 🚀 This is a big step towards making Continuous Profiling in production available to the whole industry. And given the rise of AI coding, this couldn't come at a better moment in time ... 🧵

Florian Lehner and Felix Geisendörfer presenting "The Fourth Pillar Arrives: OpenTelemetry Profiling Alpha in Action" at KubeCon EU

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Felix Geisendörfer @felixge.de · 16/12/2025

The talk @florianl.bsky.social and I submitted has been accepted at KubeCon 2026 in Amsterdam. 🎉 Small wrinkle: The talk says that the profiling signal is in alpha … which is not true yet. Fear driven development will continue until reality and talk description are aligned!

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Felix Geisendörfer @felixge.de · 10/12/2025

A small productivity hack I use every day. gist.github.com/felixge/ce96...

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Felix Geisendörfer @felixge.de · 17/09/2025

I need to start a critical path analysis art gallery soon. The kind of stuff goroutines get up to behind the scenes can be truly fascinating.

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Felix Geisendörfer @felixge.de · 17/09/2025

I'm starting to get better at leveraging AI agents for the kind of low-level stuff I'm doing sometimes. Example: Asked opus to explain some runtime internals, and then turn the analysis into a nice human-readable markdown output that I can use to explain a code change I'm making to a colleague.

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Felix Geisendörfer @felixge.de · 11/09/2025

My usual workflow is firing off the same query in ChatGPT 5 and Gemini 2.5 Pro these days. Typically they align, but one answer is better than the other. But it turns out no amount of AI can solve the "too many chefs in the kitchen" problem 😂.

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Felix Geisendörfer @felixge.de · 16/08/2025

Having fun using pikchr to generate diagrams for my critical path analysis talk at GopherCon US.

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Felix Geisendörfer @felixge.de · 01/08/2025

Just updated the proposal to use a struct based API that reuses the existing EventType structs in the trace package. Feedback welcome! 🙇🏻‍♂️

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Felix Geisendörfer @felixge.de · 31/07/2025

Wrote up a small proposal to make it easier to test code that is processing #golang execution traces using the x/exp/trace package.

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Felix Geisendörfer @felixge.de · 06/06/2025

Meanwhile ChatGPT O3 figured it out in one shot.

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Felix Geisendörfer @felixge.de · 06/06/2025

Dear @github.com I'd love to use Copilot to perform natural language search against large code bases. But it does not seem to work, no matter what model I pick.

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Felix Geisendörfer @felixge.de · 27/05/2025

Gemini's research on this, FWIW.

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Felix Geisendörfer @felixge.de · 12/03/2025

The discussion around the TypeScript migration to Go has made it obvious that we need a version of this meme with another character or two who is offended at being neither the current nor future love interest 🙈.

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Felix Geisendörfer @felixge.de · 01/03/2025

Also: Greetings from Ahlbeck on Usedom. The weather could be better, but it makes for good coding while my daughter is having her lunch naps 😅.

Picture of the beach of Ahlbeck with lots of fog.

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Felix Geisendörfer @felixge.de · 22/01/2025

Have you ever struggled with debugging memory leaks or OOM kills in Java or Go? My team at @datadoghq.com has recently shipped a guided memory leak workflow that can quickly guide you through the right steps to find and fix the problematic code.

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Felix Geisendörfer @felixge.de · 08/01/2025

My favorite aspect of OSS and sharing knowledge with the community: It all adds up to a virtuous circle. Also: If you enjoy a project with less than ~1000 stars, consider letting the author know. It's a small effort and can easily make someones day.

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Felix Geisendörfer @felixge.de · 06/12/2024

Orchestrion is open source and uses a simple, yet powerful declarative syntax for injecting instrumentation into your application at build time. Here is the declaration for instrumenting the gin web framework and how it rewrites your code behind the scenes.

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Felix Geisendörfer @felixge.de · 06/12/2024

Speaking of Security, Orchestrion has allowed us to bring advanced Runtime Application Self-Protection (RASP) to Go for the first time. For example, RASP can detect if your application calls os.OpenFile() using a user provided string and block the call if it is malicious.

A thief trying to steal an /etc/passwd file but getting blocked by RASP.

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Felix Geisendörfer @felixge.de · 06/12/2024

The whole process should take about 5 minutes and immediately gives you observability into 39 popular Go libraries. In addition to distributed tracing, you can also opt into additional features such as Profiling, Data Streams Monitoring and Application Security Monitoring.

A list of supported Go packages. See https://github.com/DataDog/orchestrion/blob/main/README.md#supported-libraries

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Felix Geisendörfer @felixge.de · 06/12/2024

Instead of using unsafe tricks to hack into a running program, Orchestrion uses compile-time instrumentation that benefits from all the type safety offered by Go’s compiler. Usage is simple: Setup a repository once, and then tell Go’s toolchain to use Orchestrion in CI.

# Setup a new repo for orchestrion on your dev machine
$ go install github.com/DataDog/orchestrion@latest
$ orchestrion pin
$ git add go.mod go.sum orchestrion.tool.go
$ git commit -m "chore: enable orchestrion"

# Auto-instrument in CI at compile time
$ export GOFLAGS="${GOFLAGS} '-toolexec=orchestrion toolexec'"
$ go test .
$ go build .

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Felix Geisendörfer @felixge.de · 06/12/2024

Manually instrumenting Go applications for observability has always been a time-consuming challenge. Solutions based on binary patching and eBPF have attempted to solve this, but they often come with undesirable tradeoffs. That’s why we built Orchestrion … 🧵

Table comparing Binary Patching, eBPF and Orchestrion for instrumenting Go applications. See blog post linked at the end of this thread for more information.

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Felix Geisendörfer @felixge.de · 26/11/2024

For go1.24 (fingers crossed) and potentially as a backport fix, I'm proposing to always show start and end stack traces which should be much more useful and make the viewer easier to use.

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Felix Geisendörfer @felixge.de · 26/11/2024

I just noticed that go tool trace slightly changed its behavior when it comes to the stack traces it displays in go1.23 compared to go1.22.

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Felix Geisendörfer @felixge.de · 30/10/2024

Is it just me, or is it normal that Bluesky is pretty slow to load stuff?

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