OBS Studio + Snap Camera: Putting yourself in your presentation live for free!

When giving online presentations, it helps for personal marketing if people can see you on the screen. Various tools provide features which help you achieve that, for example Microsoft Teams. Sometimes though you do not have that available or want to be able to do more than what the tool you are using provides. Using OBS Studio (free) with Snap Camera (free) or ChromaCam ($29.99 lifetime license) you can easily put yourself in your own presentations in such a way that it will work on almost any medium you would like to present on without having to invest in a green screen. Want to know how? Read on! 

OpenEBS: Create persistent storage in your Charmed Kubernetes cluster

I previously wrote a blog about using StorageOS as persistent storage solution for Kubernetes here. StorageOS is dependent on etcd. I was having difficulties getting etcd up again after a reboot. Since I wanted to get a storage solution working quickly and not focus too much on external dependencies so I decided to give OpenEBS a try. In this blog I'll describe a developer installation on Charmed Kubernetes (the environment described here). I used openebs-jiva-default as storage class. This is unsuitable for production scenario's. OpenEBS also provides cStor. Most of the development effort goes there. cStor however requires a mounted block device. I have not tried this yet in my environment.

StorageOS: Create persistent storage in your Charmed Kubernetes cluster

If you want to experiment with a multi node Kubernetes cluster locally as a developer, you need a distributed persistent storage solution to approximate real production scenario's. StorageOS is one of those solutions. In this blog I describe a developer installation StorageOS. For production scenario's check out the best practices mentioned on the StorageOS site.

Charmed Kubernetes on KVM using MAAS and juju

Coming to this solution was a journey. I was looking for a Kubernetes installation which was easy to deploy and cleanup on my own laptop (I didn't want to have to pay for a hosted solution). I did want a solution which was more or less production like because I wanted to be able to play with storage solutions and deal with cluster challenges / loadbalancers. Things I couldn't do easily on environments like Minikube and Microk8s. Also, since I was running on a single piece of hardware, I needed a virtualization technology. Each one of them comes with their own challenges. On some of them it is difficult to get storage solutions to work, for example LXC/LXD (an alternative to Docker). Some of them come with networking challenges like Hyper-V and some of them just don't perform well like VirtualBox. I also needed a solution to provide some form of automation to create/destroy/access my virtual environments. A long list of requirements and this is what I ended up with. A production-like environment which is quick to create, destroy or reset, running on my laptop with easy management tools.

Quick and easy: A multi-node Kubernetes cluster on CentOS 7 + QEMU/KVM (libvirt)

Kubernetes is a popular container orchestration platform. As a developer understanding the environment in which your application is going to run is important since this can help you use available services of the platform and fix issues.

There are several options to run Kubernetes locally to get some experience with Kubernetes as developer. For example Minikube, MicroK8s and MiniShift. These options however are not representative for a real environment. They for example usually do not have master and slave nodes. Running locally requires quite different configuration compared to running multiple nodes in VMs. Think for example about how to deal with storage and a container registry which you want to share over the different nodes. Installing a full blown environment requires a lot of work and resources. Using a cloud service usually is not free and you usually have less to no control over the environment Kubernetes is running in.

In this blog I'll describe a 'middle way'. Get an easy to manage small multi node Kubernetes environment running in different VMs. You can use this environment for example to learn what the challenges of clusters are and how to deal with them efficiently.

It uses the work done here with some minor additions to get a dashboard ready.

Spring: Blocking vs non-blocking: R2DBC vs JDBC and WebFlux vs Web MVC

Spring Framework version 5, released in Sept 2017, introduced Spring WebFlux. A fully reactive stack. In Dec 2019 Spring Data R2DBC, a reactive relational database driver was released. In this blog post I'll show that at high concurrency, WebFlux and R2DBC perform better. They have better response times and higher throughput. As additional benefits, they use less memory and CPU per request processed and when leaving out JPA in case of R2DBC, your fat JAR becomes a lot smaller. At high concurrency using WebFlux and R2DBC is a good idea!

The size of Docker images containing OpenJDK 11.0.6

When running Java applications in containers, you need to be careful with your resources. If you're not careful with layering your images (for example using Google's Jib), you can quickly get into disk-space issues, especially when your base image and/or application gets updated regularly. One of the ways you can save resources is by using small base images. In this blog post I determined the uncompressed size of several base images containing OpenJDK 11.0.6 which are available on Docker Hub.