mhmxs tech.log

 During the development of one of our new features, I faced an interesting challenge. The feature requests are simple and clear: there is an existing DaemonSet  (workload running on "every" node) on the target Kubernetes  cluster, we have to deploy another workload next to each instance and prevent workload termination under certain conditions. Let's split the problem into two parts; deployment and prevention. From the deployment perspective, another DaemonSet makes lots of sense. If we use the same node selectors as the existing one, Kubernetes would deploy pods to the same nodes. In our case a custom operator is working in the background, so we are able to sync node selectors, but for other kinds of deployments this should be a tricky piece. On the topic of prevention PodDisruptionBudget [PDB] comes into the picture. Without going into the details PDB allows us to define how many of the target pods should be terminated by Kubernetes at once. It has a maxUnavailable fi...

Kubernetes networking has some basic rules.  In short, every pod has to communicate with every other. Selecting the right network plugin for the cluster is a critical key component when planning and architecting a new cluster. Luckily there are great presentations and blog posts around the topic of Kubernetes cluster networking on the internet, but the available sources are very limited about how to connect external resources that aren’t part of the cluster into the mesh. It all depends on what we would like to achieve, so finally, we have to glue the solutions together. In this post, I would like to tell our story @IBM about converting an existing node to become a full member of our Kubernetes + Calico network. First of all, we had to specify the main goals: Make node full member of the overlay network The external node needs a pod IP to be able to reach it like any regular pod in the system The pod IP must be listenable for services on the external node Service discove...

Nowadays everything is Cloud Native; everybody talks about CN tools, frameworks, solutions, and so on. On the other hand, those tools totally changed the way we design, develop, test and release modern applications. I think the number of issues that we solved with the new concepts is equal to the number of new challenges, so in short,     we simply shoveled problems from one hole to the other. Many new tools appeared on the market to make developers' life easier by integrating software with the underlying infrastructure watching file changes and building containers automatically generating resource descriptors on the fly allowing debugging in a running container etc. Next to the new tools, new programming languages such as Metaparticle , Pulumi or Ballerina have been born. The last one had my attention because others are extensions on top of some existing languages, while Ballerina is a brand new programming language, des...