I have written about using an embedded database like HSQLDB or H2 for testing Java applications. This can still be useful (although JavaEE is not so popular any longer). But even though H2 claims to emulate PostgreSQL and several other popular production SQL databases, sometimes your application uses very specific features of a particular database and you need to test against the real thing to be really sure your application works correctly.

This can conveniently be done using Testcontainers, which run an instance of the real database in a Docker container for your tests. The downside is that this can be significantly slower than an embedded in-memory database like HSQLDB or H2.

I have been using the distroless Docker base images to package my applications, mainly since I want slim and simple image without unnecessary cruft.

However, they are based on Debian, and Debian is unfortunately not so diligent to fix serious security issues as other distributions like Ubuntu or Alpine. If you scan a distroless image with the grype tool, you get this result:

$ grype gcr.io/distroless/java17-debian11

NAME             INSTALLED              FIXED-IN     TYPE  VULNERABILITY     SEVERITY
libharfbuzz0b    2.7.4-1                (won't fix)  deb   CVE-2023-25193    High
libjpeg62-turbo  1:2.0.6-4              (won't fix)  deb   CVE-2021-46822    Medium
libssl1.1        1.1.1n-0+deb11u4       (won't fix)  deb   CVE-2023-0464     High
openssl          1.1.1n-0+deb11u4       (won't fix)  deb   CVE-2023-0464     High

Furthermore, if small image size is important, distroless is quite overrated. They brags about being so small:

Docker’s official documentation on how to enable multi-platform Docker builds is a bit intimidating, suggesting you to run the Docker image tonistiigi/binfmt in privileged mode on your machine. I searched for alternatives on Ubuntu, and found this very detailed description. However, with recent versions of Ubuntu and Docker, it is now much easier than that:

1. Install QEMU’s static user mode emulation binaries:
   sudo apt install qemu-user-static
2. Install Docker Engine with Buildx support according instructions here (do not install docker-ce or docker.io from Ubuntu’s standard repository).
3. Create a Docker Buildx builder:
   docker buildx create --name multiplatform --bootstrap --use
4. Verify it:
   docker buildx inspect

Then you can do multi-platform Docker builds like this:
docker buildx build --platform linux/amd64,linux/arm64 .