Docker & Java

This repo contains demo materials for:

• Tips minimize java containers images
• Tricks for fast startup java apps running in containers
• gotchas and issues while running java apps in containers and the improvements that has been made

The repo is split into multiple branches, each contains a specific topic. The Dockerfiles uses the generated jar after running the build (mvn clean package). The build step could be integrated in the provided Dockerfiles, but it would slow the demoing the intention of this repo, so I kept it outside. Below branch details:

• master: simple netty app, running in a container
• mod: Using Project Jigsaw’s jlink, that offers the ability to produce a minimal JRE based on the modules our application requires.
• alpine: based on project Portola: the community effort to port java to musl
• cdc: This showcase the class data sharing (CDS) feature. CDC offers dynamic sharing of data between multiple Java Virtual Machines (JVM), which helps to reduce the startup time and memory footprint.
• aot: [Depreicated and removed in Java 17] Using Ahead Of Time compilation. It compiles the bytecode such that it is completely static which should lead to the fastest startup and initial execution speed.
• graal: This part uses graal VM to create native images for existing JVM-based applications.
• sb: This branch contains a simple instructions to run the petclinic application and test how it behaves running inside a java 8 docker container, and java 11!

Benchmarking

the bench.sh run each container and print at the end the total size of the image + the time it takes for teh container to run! for me I named the images: plain, cdc,aot,graal, alpine and mod. I prefixed each of them with dj! Executing the scripts shows below results in my machine:

Image   size        Startup
plain    353.836MB   627 ms
mod      59.12MB     649 ms
alpine   47.0079MB   651 ms
aot      392.888MB   537 ms
cds      357.231MB   547 ms
graal    13.3264MB   3 ms