Fullstaq Ruby epic 3: CI/CD (= faster updates), Ruby updates, Debian 10 support

Fullstaq Ruby is a server-optimized Ruby distribution: 50% less memory, faster, easy to install and security-patch via APT/YUM.

We've reached an important milestone in the Fullstaq Ruby roadmap. Epic 3 introduces a continuous integration and deployment system! This means that from now on, we can release updates much faster, and with fewer defects.

We put the CI/CD system to the test right away, and used it to release Ruby version updates. We now package Ruby 2.7.1, 2.6.6 and 2.5.8.

Additionally, we now support Debian 10 (contributed by Nathan Broadbent).

Want to install or upgrade? Check the installation instructions, or run apt upgrade/yum update.

In this article I'll explain why having a CI/CD system is so important. I'll also give you a sneak peek into what to expect in the near future.

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A better way to reason about software testing terms

I was recently in a discussion between developers about improving the test coverage of a major software project. They needed guidance about what kind of tests to write, and how to write them.

The discussion quickly became confusing: the topic was too large, too general, and it turns out that there wasn't even a well-defined shared vocabulary for testing concepts! The latter turns out to be a wider problem in the software development community: it simply doesn't have well-defined testing terms!

In this post, I'd like to provide some guidance w.r.t. this matter. I'll discuss:

  • An overview of the most common testing terms.
  • A new way of reasoning about testing concepts: reiterating what actually matters, and categorizing tests based on "size" and "approach".
  • How the existing testing terminology fits in this new model.

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Debugging Docker builds

One of the projects I'm working on has a CI/CD pipeline that builds Docker images. The Dockerfile runs yarn install, then yarn build. The latter runs the TypeScript compiler tsc. Everything was working fine, but one day the build failed with the following error:

tsc: command not found

But TypeScript is still part of package.json. Nobody touched package.json or yarn.lock recently. Nobody could reproduce the problem locally with Docker: it only happened in the CI/CD pipeline. What is going on? We needed to debug the Docker build on the CI/CD server.

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Software development is like surgery

Estimating how long it takes to build software – or even how much effort a sprint is – is pretty hard. Estimates often turn out to be too optimistic, and mispredictions can be pretty hard to explain to management. I know why this is so – Michael Wolfe on Quora has a great analogy (there is even an interesting discussion on Reddit), which I agree with. But I'm wondering whether there's an easier analogy.

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EuRuKo 2019 was lots of fun

EuRuKo 2019 – the largest Ruby conference in Europe, took place on the 21st and 22nd of June. I gave a talk on the 21st about what causes Ruby memory bloat (where I also reported new findings since I first blogged about the issue), as well as about Fullstaq Ruby. Fullstaq Ruby is a server-optimized Ruby distribution that's faster, uses less memory, and is easier to security-patch thanks to being distributed via RPMs and DEBs.

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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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