Featured posts


What causes Ruby memory bloat?

Ruby apps can use a lot of memory. But why? Various people in the community attribute it to memory fragmentation, and provide two “hacky” solutions. Dissatisfied by the current explanations and provided solutions, I set out on a journey to discover the deeper truth and to find better solutions.

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Full-system dynamic tracing on Linux using eBPF and bpftrace

Linux has two well-known tracing tools:

  • strace allows you to see what system calls are being made.
  • ltrace allows you to see what dynamic library calls are being made.

Though useful, these tools are limited. What if you want to trace what happens inside a system call or library call? What if you want to do more than just logging calls, e.g. you want to compile statistics on certain behavior? What if you want to trace multiple processes and correlate data from multiple sources?

In 2019, there's finally a decent answer to that on Linux: bpftrace, based on eBPF technology. Bpftrace allows you to write small programs that execute whenever an event occurs.

This article shows you how to setup bpftrace and teaches you its basic usage. I'll also give an overview of how the tracing ecosystem looks like (e.g. "what's eBPF?") and how it came to be what it is today.

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How to build a good company purpose?

It has often been stated by business consultants and startup advisors that a company should have a purpose beyond vision. Studies show that that result in more motivated and loyal customers and employees. As Simon Sinek said: people don’t buy or follow what you do, but why you do it.

I agree. That was the easy part. But how do you actually define a good purpose? People need to feel that your purpose is aligned with their own values, and a purpose statement needs to balance many different things for many different people.

This post documents the start of my journey in an attempt to find answers.

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Studying the Kubernetes Ingress system

I have been researching how the Kubernetes Ingress system works. My use case is to setup an autoscaled Nginx cluster that reverse proxies to Pods in multiple Deployments. It wasn't immediately obvious how to do this. By default, Pods in Kubernetes are not supposed to be reachable from outside the cluster. One makes them reachable either by associating those pods with a Service of the right type (i.e. either NodePort or LoadBalancer), or by defining an Ingress. But what is an Ingress? How do I put Nginx in between an Ingress and a set of Pods? This post describes my journey through the jargon-loaded Kubernetes documentation which does not hold any hands, as well as my journey through the Kubernetes source code, all in a quest to find answers.

This post a bit long, so if you just want a summary then you can skip straight to the conclusion at the bottom.

Kubernetes nginx ingress problem
Defining a Service is straightforward enough... but how do you point Nginx to that? And how does Nginx relate to this Ingress thing?

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In appreciation of Prometheus' engineering

Even though I rejected Prometheus as a choice in my last blog post about Netdata, I actually appreciate Prometheus' engineering quality. From its documentation it is apparent that the authors are very experienced on the subject and have thought through things.

This post reviews some of the things that demonstrate that, namely their responses to the push vs pull debacle, the way they limit Prometheus' scope, the way their alerting system is designed and documented, and the way they treat storage.

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