Java: Native Memory Handling is Getting Easier

May 15, 2023

JDK 19, 20, 21 has a new preview API called 'Foreign Function & Memory API' that makes interacting with native memory and native libraries way easier. Before you had to use JNI, JNA or JNR to interact with native libraries.

Further, interacting with 'native' memory was clunky. You either used ByteBuffers, which have a clunky/dated API, max addressable size 2GByte plus 'freeing' relying on the GC, unless you do ugly reflection hacks. Or you went down the Unsafe route.

Anyway, if your projects allows, I would heavily recommend to the new APIs. If it is a project you deploy in your backend, you can control the JDK. If it is a new library, I would still think about starting/consider the new APIs, so that the library can be kick ass by the time it is mature.

Waiting for Response
Figure 1. Memory Hunger
Continue reading →

Mysterious Hanging Java Process

April 15, 2023

I recently had a Java (Bamboo Dev Instance) app just hanging when it started up. Since it was a dev setup, which sometimes has other issues, I did the usual things, like:

  • Turn it on and off again, aka restart it.

  • Clean up the working directory, like a mvn clean, make clean or what ever.

  • Check out a stable branch.

  • Run against different sets of dependency versions

The app kept on being stuck. So, I was forced to debug it =).

Waiting for Response
Figure 1. Hanging Process
Continue reading →

Test Containers for C#/.NET

December 22, 2022

This post is part of C# Advent Calendar 2022.

Many applications lean heavily on relation database. Your application uses complex queries, constrains on data and all more of the wonderful features of a relation database. That means that a lot of your applications behavior depends on how the database acts.

Therefore, I try to test an against actual database system. Years ago this used to be a challenge, as most database systems where hard to setup and automate.
Today it is easy. Use TestContainers!

Test Containers

TestContainers is a library which starts up Docker containers for your tests. More, it provides many pre-configured setups for databases.

Joy of Test Containers
Figure 1. Joy of Test Containers
Continue reading →

Redis Clone: Reducing Memory Pressure

September 13, 2022

After the taking a look at the original naive implementation, I wanted to try reducing the memory churn. By accident the IO optimizations already reduced the memory usage. Let’s go a bit further, trimming down some memory usage.

I often look out for two things: - Object allocations of objects which are immediately thrown away again. Yes, the JVM allocator and GC do an amazing job handling short-lived objects. However, it’s not magic and the memory bandwidth is limited. So, removing unnecessary short-lived objects is often easy and gives you more memory bandwidth headroom. - Ensuring long-lived objects are in a compact form and a useful format for the purpose.

Reduce Memory Waste
Figure 1. Reduce Memory Waste

Anyway, I’m trying to shave off some allocations in this blog post. Note, as I reduce allocations the code becomes less Java-y and I introduce C-like fragility, where life-time of memory matters. In a real-world app I would only use such optimizations only if you really need more performance.

Continue reading →

Creating Pseudo Terminals for Test Scripts with tmux

August 29, 2022

I recently tried to automate a test setup, where the program I tried to automate insisted on having a TTY. Oh no, yet another TTY adventure (previous one) for me ;).

Puppeteering TTYs
Figure 1. Puppeteering TTYs
Continue reading →