zignar.net

Profiling Cheatsheet

2025-09-23T00:00:00Z

This is a short overview - or reference - on how I tend to do quick application profiling.

Dealing with flaky tests

2025-06-26T00:00:00Z

In my work I’m often dealing with flaky tests due to race conditions. Here are a few things I’ve picked up along the way that can help to deal with them.

The Debug Adapter Protocol is a REPL protocol in disguise

2025-06-23T00:00:00Z

A couple months back I created nluarepl. It’s a REPL for the Neovim Lua interpreter with a little twist: It’s using the Debug Adapter Protocol. And before that, I worked on hprofdap. Also a kind of a REPL using DAP that lets you inspect Java heap dumps (.hprof files) using OQL.

As the name might imply, a REPL isn’t the main use case for the Debug Adapter Protocol (DAP). From the DAP page:

The idea behind the Debug Adapter Protocol (DAP) is to abstract the way how the debugging support of development tools communicates with debuggers or runtimes into a protocol.

But it works surprisingly well for a REPL interface to a language interpreter too.

No-Config Python debugging using Neovim

2025-03-02T00:00:00Z

A little while ago Microsoft released No Config Debugging functionality in their vscode python extension.

This got me curious - wondering if it can be replicated in Neovim. Turns out it can be. This post shows how.

Template files for nvim

2024-11-20T00:00:00Z

Over the years I’ve picked up various tweaks for my nvim configuration. One of them is template file support. This article is a short introduction to what they are, how do they work and how I recently extended them to support snippet expansion.

Debugging Lua in Neovim

2023-06-10T00:00:00Z

In this post I want to show you how you can debug Lua scripts with Neovim and nvim-dap. Both regular Lua, but also Lua that uses Neovim as Lua interpreter. The latter is interesting if you want to debug Neovim plugin test cases written using busted

Debugging Neovim with Neovim and nvim-dap

2023-02-17T00:00:00Z

Recently a change got merged in Neovim that decoupled its TUI from the main process. A side effect of the change is that debugging it became a bit more troublesome. It now forks itself and you end up with two processes. Depending on what you want to debug you need to attach to that second process.

I thought this might be an interesting use-case for more advanced features of nvim-dap. This post explores using it to automate attaching to the second process.

Even if you’ll never debug Neovim you may find this interesting as it could give you some ideas on what you can do with a hackable debugger.

This post uses nvim-dap features of the upcoming 0.5 release. If you’re on 0.4 you’ll have to switch to the development branch. (If you are from the future, use 0.5+)

Using Neovim as Lua interpreter with Luarocks

2023-01-21T00:00:00Z

This is a short article covering how you can use Neovim as Lua interpreter for Luarocks and busted.

Structuring Neovim Lua plugins

2022-11-06T00:00:00Z

This is an introduction to the various ways you can structure a Neovim plugin and their trade-offs.

Testing Neovim LSP plugins

2022-10-26T00:00:00Z

This is a short introduction in how you can test a Neovim plugin which extends the LSP functionality. This approach requires Neovim 0.8 or later.

New LSP features in Neovim 0.8

2022-10-01T00:00:00Z

Neovim 0.8 got released the other day, time to write about some of the LSP changes.

Using tshark to monitor PostgreSQL traffic

2022-09-24T00:00:00Z

As part of my work on CrateDB I occasionally have to debug its PostgreSQL wire protocol implementation. One tool that has been incredibly helpful for that is tshark, which is part of Wireshark.

A tree sitting in your editor

2022-09-02T00:00:00Z

This is a short introduction to the tree-sitter integration in Neovim based on a use-case I had: To find content in a TOML file close to the cursor position and then launch an application using this information.

Can you write a CLI using Java?

2022-05-14T00:00:00Z

A recent conversation got me curious about how people feel about writing command line applications in Java.

I knew that Java for many isn’t the first choice when thinking of building a CLI, but I was curious if people consider it an option at all. I started a poll on Twitter. Only 19 people participated, but the outcome was quite clear:

Java is a good choice to write command line applications

Option	Votes
Agree	5.3%
Disagree	68.4%
No way, are you crazy	26.3%

If you asked me several years ago I’d have had a similar reaction, but in 2022 I’m not so sure anymore.

Reading science papers on a Remarkable

2022-01-27T00:00:00Z

A while ago I damaged my old tablet and got a Remarkable 2 as replacement. One of the use-cases for my old tablet was reading science papers. The remarkable can read PDFs and EPUB files and with a 10.3” screen it’s one of the larger eink devices on the market.

Computer science papers often use a 2-column layout, small font and large margins. It’s possible to read, but despite the screen size it wasn’t the most pleasant experience. It would be more convenient if we could re-arrange and re-flow the text.

Turns out we can.

A boring statusline for Neovim

2022-01-21T00:00:00Z

There a dozen of statusline plugins for neovim: express_line, galaxyline, lualine, statusline, windline and possibly more. Each with different goals and feature sets. This article isn’t about any of them, instead we look at the built-in statusline option and how you can use it to create a boring but functional status line.

Building a web 3.0 Twitter clone

2021-12-25T00:00:00Z

I am pretty certain that the whole web 3.0 story is a mind-bogglingly stupid idea, but I like to challenge my own views. I thought one way to do that is to explore how I’d build a web 3.0 twitter clone. This post is this exploration. I’ll try to suppress my bias as best I can.

Help people help you and put in some effort

2021-12-03T00:00:00Z

This article is for you if you either:

Created an issue or bug report that boils down to “XY doesn’t work. Help me”
Entered a chat room and wrote “XY doesn’t work. Help me”
Trying to get help but nobody is answering

Why Haskell became my favorite scripting language

2021-07-09T00:00:00Z

I started learning Haskell a couple of years ago. My usual reason to learn a programming language is because I have a concrete use-case - a project I want to contribute to. With Haskell it was different. My primary motivation wasn’t a concrete use-case, but instead I thought studying the language would be worth it for the sake of learning. It does things different than other mainstream languages and I wanted to become familiar with concepts I hadn’t seen before.

Writing a couple of iterations of “Hello World” applications wasn’t going to get me far. Utilizing it in a project at work wasn’t an option - instead I started using it for my ad-hoc and utility scripts. Before, Python was my go-to language for such things, but Haskell ended up replacing it. In this article I will show why.

The Circuit Breaker mechanism in CrateDB

2021-06-17T00:00:00Z

In this article we’ll take a look at the circuit breaker mechanism in CrateDB. CrateDB uses circuit breakers to prevent a node from running out of memory or stalling due to high garbage collection load.

Group By query execution in CrateDB

2021-06-04T00:00:00Z

In this post we’ll look at how CrateDB distributes GROUP BY queries. This is the fourth post in a series about CrateDB internals.

I assume that you’ve read the first and second post of the series. You may also be interested in the third post, but it is not necessary to read it to follow this article.

Query Then Fetch execution in CrateDB

2021-05-28T00:00:00Z

This is the third post in a series about CrateDB internals. This time I’ll introduce the Query Then Fetch execution strategy. Similar to the previous posts, this focuses on the distribution aspect.

Make sure to read the first and second post of the series.

Distributed SELECT statement execution in CrateDB

2021-05-20T00:00:00Z

This is the second post of a series about CrateDB internals. In the first post I introduced relational algebra, the optimizer and outlined how the execution works on a very high level. In this post I’ll explore the execution of a simple SELECT statement in more detail. This post focuses on the distribution aspect of the query execution.

How CrateDB plans and executes queries

2021-05-15T00:00:00Z

This post is the first of a series that explains how CrateDB executes queries. This first post focuses on the optimizer, logical plan and execution plan.

Neovim completion plugin building blocks

2021-05-14T00:00:00Z

In this post I’ll show you the basic building blocks of a completion plugin for Neovim.

Avoid shallow functions

2021-05-14T00:00:00Z

Over the last couple of years I developed an intuition that shallow functions can be problematic and here I’d like to share some thoughts on why.

Are you asking too many questions, or not enough?

2021-04-15T00:00:00Z

Two scenarios that may sound familiar:

You’re in an office space and there is this one person who always asks questions that they could answer on their own by spending two minutes using ~~Google~~ DuckDuckGo. He feels super productive because he’s getting answers quickly, but the senior who has to answer starts getting annoyed by all the micro interruptions. It makes it hard for her to focus.
A new person joins a team, and they hardly ask any questions. Instead, they spend hours trying to figure out everything on their own.

Triggering Jenkins jobs from the command line

2021-02-25T00:00:00Z

It occurred to me that many people do not know that it is possible to trigger Jenkins jobs from the command line. But it is possible and all you need is a SSH client. Here is a short introduction on how to get it working.

Arguing about taste

2021-01-22T00:00:00Z

Yellow is the best color.

Elastic moving to SSPL and making money with open source

2021-01-16T00:00:00Z

A couple of days ago Elastic announced that they’re moving their Apache 2.0 licensed code in Elasticsearch and Kibana to be dual licensed under the Server Side Public License (SSPL) and the Elastic License.

Working on the right task and managing energy levels

2021-01-01T00:00:00Z

Over the last couple of years I’ve often heard that somebody shouldn’t spend time doing X, but rather focus on doing Y. Here I explore three reasons that may explain why people work on the “wrong” tasks.

Adding the pg_catalog.pg_am system table to CrateDB

2020-12-09T00:00:00Z

In this article I’ll show you how I added the pg_catalog.pg_am system table to CrateDB.

Why you should keep a clean git history

2020-11-14T00:00:00Z

There are still many software projects that don’t care about keeping a clean git history. I think that is a pity. Here I show you a couple of reasons explaining why it is beneficial to keep a clean git history.

Neovim under the hood - Understanding the language server client

2020-10-27T00:00:00Z

This is a short introduction to the language server-client architecture in Neovim and how to customize the diagnostics display.

Setup Neovim for Java Development Part 2

2020-10-17T00:00:00Z

This is an updated version of an older article about setting up Neovim for Java development.

Generating Data Sets Using mkjson

2020-05-01T00:00:00Z

As a developer working on a database, I often need access to a data set to test various features. Initially, I created cr8 insert-fake-data to solve this problem. cr8 insert-fake-data reads the schema of a table and then utilizes the faker library to generate random records that match the table’s schema and inserts them.

cr8 insert-fake-data is easy to use and often accomplishes exactly what I need. However, in some cases, it is not as flexible as I need it to be, which led me to create mkjson, another tool to generate random records.

From synchronous planning to Hammock Driven Development

2020-03-22T00:00:00Z

I was first introduced to Hammock Driven Development several years ago, watching Rich Hickey’s talk. The idea stuck with me ever since.

Install scripts: A maybe not so good idea

2020-03-10T00:00:00Z

Many software projects offer a script to install the application with a single command. For CrateDB we have one as well and I think it was a mistake to create one.

Building Features Nobody Asked For

2020-02-17T00:00:00Z

Over the last couple of years, several acquaintances approached me for help with an issue they had with their phone. Each time the phone ran some kind of customized Android. Sometimes it was heavily modified. Compared to stock Android the modifications made the user experience worse. That left me puzzled. Why do companies put so much effort into features that end up deteriorating the product?

They don’t do it intentionally - at least I’d hope - but why does that happen? I think I have an answer: They become too disconnected from their users.

Asynchronous Planning Poker

2020-02-01T00:00:00Z

For a while now we’ve experimented with asynchronous planning poker. Here I want to share how it works and why we started using it instead of traditional synchronous planning poker.

Asynchronous Communication And The Curse Of Knowledge

2020-01-25T00:00:00Z

The curse of knowledge is a cognitive bias that occurs when an individual unknowingly assumes that the others have the background to understand.

Setup Neovim for Java development

2019-11-21T00:00:00Z

A writeup of how I’ve setup Neovim for Java development

(There is a newer version of this article available)

Running Steamlink on Arch Linux ARM

2019-11-10T00:00:00Z

Here is a short guide how to install steamlink on a Raspberry PI running Arch Linux ARM.

Are sprint commitments necessary?

2019-02-09T00:00:00Z

I’ve had a draft called “Is scrum the best we can do” lying around for months and the chance to finish it is tiny. So I decided to extract parts of it: Some thoughts on whether sprint commitments are beneficial or not.

TL;DR: Maybe, it depends.

Performance Theory 101 for insert throughput scaling with CrateDB

2019-01-28T00:00:00Z

This is a short introduction on how to apply a bit of performance theory in the context of tuning insert throughput performance in CrateDB.

Premature optimization isn’t the root of all evil

2016-04-07T00:00:00Z

Ask a question regarding the performance characteristic of some piece of code on the Internet and you’ll end up reading an answer along the lines of “premature optimization is the root of all evil”.

I’m starting to get sick of reading those answers. Optimizations aren’t evil.

(Abusing) Elasticsearch as a Framework

2016-03-18T00:00:00Z

Or how Crate uses Elasticsearch.

Most people who know Elasticsearch think of it as a search engine, and they’re probably correct. But we at Crate think about it a bit differently and use it as a framework.

In this post I’ll try to explain how that works.

Home Audio Using HifiBerry And Raspberry Pi

2016-03-01T00:00:00Z

In this post I’ll describe how to set up the audio system that has been doing its work happily in my living room for about a year now.

IPython %magic

2016-01-16T00:00:00Z

IPython is a more powerful interactive shell for python.

In this post I’ll explore some of my favorite IPython features.

Sniffing HTTPS traffic of a virtualbox guest VM using mitmproxy

2015-12-31T00:00:00Z

In this article I’ll show you how HTTPS traffic from a virtualbox guest vm can be routed through mitmproxy in order to sniff HTTPS traffic.

This might be useful, for example, if you wanted to figure out how a JSON API works that you know an application that you’ve installed uses.

Building SQL Auto Completion - Funday at CrateIO

2014-10-07T00:00:00Z

At Crate we’ve recently introduced something that we call “Funday”. It is probably similar to what Google has been doing with their “20%” time. In this Post I will take a deep dive into the Crate core and explain how I used that time to build an auto completion mechanism for SQL statements.

Getting started with D-Bus using Python and systemd

2014-09-08T00:00:00Z

In this post I’ll take a look at how to get started with D-Bus using Python and systemd.

Running Crate Data on CoreOS and Docker

2014-09-02T00:00:00Z

Recently I’ve been playing around with CoreOS which is a fairly new Linux distribution. Opposed to other new distributions that keep popping up CoreOS brings some interesting new ideas and does a whole lot different than conventional distributions.

Linux on a MacBook Air 2012

2012-12-20T00:00:00Z

It’s now almost two months since I’ve got my MacBook Air. Time to write up a little review.

Install Python, Pip and Virtualenv on Windows

2012-06-17T00:00:00Z

Installing Python on Windows isn’t rocket science. Here are 3 easy steps to get a complete Python environment on a Windows machine.

Sending a fax using Linux, a fritzbox and VOIP

2012-04-16T00:00:00Z

Sending a fax using capifax is actually pretty easy, except it isn’t.

ActiveSync on Linux using z-push, nginx and an imap backend

2012-04-14T00:00:00Z

Want to extend your private IMAP server with push email functionality for your smartphone? Then Z-Push might be exactly what you need.

Going Paperless

2012-04-08T00:00:00Z

It’s 2012 and I still keep folders full of papers. Time to change that.

Good ideas aren’t as important as you think they are

2012-03-21T00:00:00Z

Yesterday I’ve had an interesting although short conversation with a long time friend. One of those conversations that are usually accompanied with a couple of beers where you talk about life, the universe and everything.

EF 4.1 - Loading related Entities on type mismatch

2012-02-20T00:00:00Z

While working with Entity Framework has improved quite a bit since it’s first release, sometimes I still encounter some behaviors that are rather strange. Consider the following model. A simple one-to-many relationship. One item can be in many reports.

Baancomplete 0.2

2012-02-14T00:00:00Z

I just pushed version 0.2 to github and vim.org.

Our inability to make decisions

2012-01-31T00:00:00Z

In an earlier post I mentioned that we are bad at making rational decisions. Well, I’ve found a presentation from Dan Ariely that gives some more details about that. So for anyone who got curios after reading my post. Go ahead and watch it.

I use this #2

2012-01-28T00:00:00Z

I promised that there would be another post about my windows environment. I keep my word, so here you go.

I use this #1

2012-01-14T00:00:00Z

Great tools enable programmers to build great stuff. I think every programmer should invest at least some time into his toolbox. Read on if you’re interesting in what I use. This post is about my linux setup, there will be another post about my windows environment.

Too many choices considered harmful

2011-12-28T00:00:00Z

I think it was in the book Made to Stick where they proposed the idea that given too many choices we tend to make poor decisions. And “too many” can be as few as three. As a software developer that has to constantly make tiny, little or major decisions I tend to agree with that idea.

Copy data from Mysql to Postgres Part 2

2011-11-01T00:00:00Z

I showed you in my last post how to move data from mysql to postgres by using sqlalchemy. But that technique requires sqlalchemy metadata. What if you don’t have them?

Copy data from Mysql to Postgres using SqlAlchemy

2011-11-01T00:00:00Z

As I mentioned earlier I had somehow to move my data from Mysql to Postgres. There is a Wiki full of documentation on how to do that. But before falling back to a finished solution I wanted to get my hands dirty by utilizing sqlalchemy.

Chocolatey - A package manager for windows

2011-10-23T00:00:00Z

For a change I got something for windows users today.

Migrations Xen, Wheezy, Postgres and Python3

2011-10-22T00:00:00Z

The last couple of days I have been busy migrating my vserver.

Syntax highlighting for less

2011-09-25T00:00:00Z

Sometimes I happen to come across things that I didn’t know I need until I see them. One of these things is the ability to have syntax highlighting within less. The package that makes this possible is src-highlite. Under Archlinux it is packaged as source-highlight.

Baancomplete

2011-09-20T00:00:00Z

I just published the first version of a vim plugin that was my pet project for the last two weeks. It adds omni-completion for the baan scripting language.