Running a private container registry for testing

When I signed up for my DockerHub account in 2013, I never thought sooner than later everything ends up in a container image as it is today. DockerHub was the first public free as in free beer registry to distribute your container images. Containers are now everywhere, and DockerHub, a corporate entity running and funding DockerHub, introduced usage limits for the free tier and started commercializing its registry service. I need to play with software in a micro-service architecture on a platform like Kubernetes, and these limits can be daunting. Continue reading

Docker build and cache invalidation

Right now I’m working with my work mates @opennms integrating the docker image building in our CI/CD environment. We build our container image based on CentOS and we noticed the caching doesn’t work for ${reasons}. Running a docker build -t myimage . ended up always in installing packages from the official yum repositories even we haven’t changed anything in the Dockerfile. To understand things better, I went back to drawing board and started with a simple example and rebuilding things step by step to understand when gets the docker build cache unnecessarily invalidated. Continue reading

Docker, Java, Signals and Pid 1

Running a Java application in a container seems to be very easy. The devil is in the details and I want to shed some light on the PID 1 problem when you run Java applications in containers. In a general running applications in containers should not have any state so you just don’t care, but reality is different forces you to have to. Signals are used to a running process to behave in a certain ways. Continue reading