Super-short instructions how to place the breakpoint in an IDE in order to debug CORS issues in Spring Boot. The problem with debugging CORS (like any other filter in spring boot security) is, that any request is blocked before they…
Debugging Angular with Visual Studio Code (Cheat Sheet)
Find below quick step by step instructions on how to debug Angular applications with Visual Studio Code. Versions Tested on Visual Studio Code v1.52.1 on CentOS 7 (more recent versions do not work on CentOS 7) tldr; Ctrl-Shift+` & Create…
CKA Labs (19): Kubernetes Logging
In this article, we will have a look at Kubernetes logging. We will look, how Kubernetes logging is related to Docker logging. References: kubernetes.io: Logging Architecture Docker Logging: A Complete Guide by sematext.com Docker's official documentation on Logging Step 0:…
Tracing iptables on CentOS – Cheat sheet
This is a small cheat sheet that may help to troubleshoot iptables on CentOS systems. Most of the other articles on the Internet did not work, because CentOS has changed the way of activating tracing. Prerequisites iptables is installed and…
Avoid Docker created Files with wrong Permissions (Maven example)
This article helps you running Docker containers without polluting your filesystem with files owned by root. Most Docker images you find on Docker hub are designed to run as root inside the container. This can lead to your file system…
Hello Java Hipster: Angular 8 and Spring Boot 2.1 with Cassandra 3.11 running in Docker
Two and a half years ago, we have shown in this blog post how JHipster a.k.a. Java Hipster can be used to auto-generate Angular 4 and Spring Boot code. Now, we will revisit the Hello World with newer versions Angular…
Install NPM using Chocolatey on Windows
In this little article, we show how to install NPM on Windows using Chocolatey, which is a Linux-like packet manager like apt-get, yum & Co. Step 1: Install Chocolatey on Windows We are following the installation instructions on https://chocolatey.org/install: Step…
Jest@Angular – Replacing Karma by Jest
Improve Angular unit test performance and learn how to replace Karma by Jest right after creating a new project with Angular CLI.
CKA Labs (17): Kubernetes Readiness and Liveness Probes
In this article, we will learn how Kubernetes Liveness Probes and Kubernetes Readiness Probes help us improve the continuity and availability of Kubernetes Services. For that, we will learn how Kubernetes uses probes to decide, whether an application is up…
CKA Labs (18): Kubernetes Metrics Server for CPU and Memory Monitoring
Install and explore the Kubernetes Metrics Server in a hands-on lab. View the CPU and Memory consumption of cluster nodes, applications, and containers.
CKA Labs (16): Kubernetes Persistent Volumes
In this article, we will create Kubernetes Persistent Volumes, change access modes, and add Kubernetes Persistent Volume Claims. Moreover, we will gain some understanding of Kubernetes Storage Objects.
CKA Labs (15): Kubernetes Ingress
We use NginX-based Kubernetes Ingress Controllers to make Kubernetes Services available to the outside world. In our example, three separate applications share the same IP address and port. We show, how to retrieve the NginX configuration from the Ingress Controller. Moreover, we show how to install a newer NginX version provided by NginX INC.
CKA Labs (14): Kubernetes Affinity and Anti-Affinity
How to get hands-on experience with Kubernetes affinity and anti-affinity for both, node affinity as well as POD affinity for "soft" and "hard" rules.
CKA Labs (13): Kubernetes Taints and Tolerations
In this blog post, we will get hands-on experience on Kubernetes taints and tolerations. Taints are used to repel PODs from running on a certain set of nodes, while tolerations in the POD's specification allows the POD to ignore the corresponding matching taint.
CKA Labs (12): Kubernetes Labels and Node Selectors
Tutorial with a hands-on lab on Kubernetes Labels and Node Selectors, which are used to control, which PODs are scheduled on which set of Kubernetes Nodes.
CKA Labs (11) — Kubernetes Services
Kubernetes Services provide us with a means to load-balance between many instances of an application running on a data center. Moreover, they help make accessible the service from the Internet. Here, we will show, how PODs, endpoints, container-ports, and node ports are bound together by means of Kubwernetes Services.
CKA Labs (10) — Kubernetes DaemonSets
In this blog post, we have created a Kubernetes DaemonSet. We have observed that and POD template changes are not propagated to existing PODs if we choose the OnDelete update strategy. However, if we choose the RollingUpdate strategy, POD renewal is triggered with any update of the DaemonSet's POD template.
CKA Labs (9) — Kubernetes Deployments
In this blog post, we will have a closer look to Deployments, how they relate to ReplicaSets of the last post, and which features in terms of the rollout/rollback they offer to the Kubernetes administrator.
CKA Labs (8) — Kubernetes ReplicaSets
In this lab, we will have a closer look at Kubernetes Replicasets. First, we will learn how ReplicaSets control, how many POD replicas are up and running at any time. We will learn, how ReplicaSets and PODs are connected: via labels. We will show that manually creating PODs with matching labels can have weird cuckoo's eggs effects. Moreover, a POD can be detached from a ReplicaSet without stopping it by manipulating its label.
CKA Labs (7) — Kubernetes Jobs and CronJobs
In this Kubernetes lab, we will explore Kubernetes Jobs and CronJobs. Unlike Kubernetes Deployments, Kubernetes Jobs are designed to quit after they have accomplished the task (successful or not). Kubernetes CronJobs are the jobs that are repeated according to a schedule pattern Linux administrators know from crontab.