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Creating a Messaging App Using Spring for Apache Kafka, Part 5

By Kürşat Kutlu Aydemir
October 31, 2022

I guess this is the longest break between posts in this series. But finally I had a chance to prepare a working example to finalize this series. So, up-to-date code is available in the GitHub repository.

Activation and Login

This was already implemented in the previous parts. However, we haven’t shown it in action yet. There are some code fixes and small changes within the workflow of activation and login steps, so you can refer to the GitHub repository for the latest code.

Authentication and activation are managed through the AuthController class where these activation and login requests are handled. Let’s take a look at the REST endpoints handling these requests and explain the steps.

Activation

Our activation step uses a dummy mobile phone number. You can think of it similarly to activating a messaging application (like WhatsApp) using a phone number. I didn’t introduce any restrictions on the phone number for this application, so the phone number activation is just a pseudo-step and you can supply any number. In real life, the phone number activation would use SMS or other activation services to activate your chat application against the user’s phone …

Kubernetes Volume definition defaults to EmptyDir type with wrong capitalization of hostPath

By Ron Phipps
October 26, 2022

Photo by Garrett Skinner

Kubernetes Host Path volume mounts allow accessing a host system directory inside of a pod, which is helpful when doing development, for example to access the frequently-changing source code of an application being actively developed. This allows a developer to edit the code with their normal set of tools without having to jump through a bunch of hoops to get the code into a pod.

We use this setup at End Point in development where the host system is running MicroK8s and there is a single pod for an application on a single node. In most other cases, host path volume mounts are not recommended. But here it means the developer can edit code on the host machine and the changes are immediately reflected within the pod without having to deploy a new image. If the application server running within the pod is also running in development mode with dynamic reloading, the changes can be viewed with a refresh of the browser accessing the application.

While working on a test environment to run EpiTrax within Kubernetes, the need arose to set up a Host Path volume mount so that the source code on the host machine would be available within the pod. I used this simple …

Knocking on Kubernetes’s Door (Ingress)

By Jeffry Johar
October 20, 2022

Photo by Alberto Capparelli

According to the Merriam-Webster dictionary, the meaning of ingress is the act of entering or entrance. In the context of Kubernetes, Ingress is a resource that enables clients or users to access the services which reside in a Kubernetes cluster. Thus Ingress is the entrance to a Kubernetes cluster! Let’s get to know more about it and test it out.

Prerequisites

We are going to deploy Nginx Ingress at Kubernetes on Docker Desktop. Thus the following are the requirements:

• Docker Desktop with Kubernetes enabled. If you are not sure how to do this, please refer to my previous blog on Docker Desktop and Kubernetes.
• Internet access to download the required YAML and Docker Images.
• git command to clone a Git repository.
• A decent editor such as Vim or Notepad++ to view and edit the YAML.

Ingress and friends

To understand why we need Ingress, we need to know 2 other resources and their shortcomings in exposing Kubernetes services. Those 2 resources are NodePort and LoadBalancer. Then we will go over the details of Ingress.

NodePort

NodePort is a type of Kubernetes service which exposes the Kubernetes application at high-numbered ports. By default the range is …

University of Denver and VisionPort: The Classroom of the 21st Century

By Samuel Stern
October 18, 2022

VisionPort’s recent installation at the University of Denver is transforming education and has even found itself featured in Forbes.

Installed in the Marion J. Crean Collaboratory room, VisionPort is doing what it does best: engaging audiences and bringing ideas to life.

The Collaboratory room gets its name from its mission, to be a collaborative laboratory, specifically for DU’s real estate and construction management students.

VisionPort was designed with geographic information systems (GIS) in mind, and the content management system we built from the ground up allows experts and novices alike to explore real estate and construction opportunities. From flying around undeveloped land, to exploring cityscapes in three dimensions, the VisionPort is the best platform for presenting GIS data.

“What [the VisionPort] is going to give us is the opportunity to sit in class, and literally, be able to fly to any property, anywhere in the world, and walk that property, see that property.” —Dr. Barbara Jackson

Seven displays spanning 18 feet, installed in a custom case on top of a beautiful wood stage, the Collaboratory’s design is one of the most unique and intriguing yet.

The world is …

Upgrading PostgreSQL 14 to 15 on Fedora, RHEL, CentOS, Rocky, Alma Linux with PGDG RPM packages

By Jon Jensen
October 14, 2022

PostgreSQL 15 changes

Yesterday PostgreSQL 15 was released! It includes a number of headline features since version 14 that make it worth upgrading your databases running earlier versions of PostgreSQL:

• Improved sort performance
• In-memory statistics collection (removing the statistics collector process)
• SQL-standard MERGE syntax that can include INSERT, UPDATE, and DELETE actions in a single statement
• Logical replication publisher options to include all tables in a schema (including those added in the future), row filtering and column lists, and simplified conflict management
• JSON format log output (to files only, not syslog)
• Optional LZ4 and Zstandard compression for WAL (write-ahead log) files, especially useful for those not using btrfs or zfs filesystem built-in compression
• New regular expression functions regexp_count, regexp_instr, regexp_like, and regexp_substr
• And many other performance improvements and feature enhancements

Thanks to the PostgreSQL developers for the continuing amazing work!

Prerequisites for upgrading

This article shows how to upgrade to PostgreSQL 15 if you:

• are running one of the Red Hat family of Linux operating systems, including Fedora, Red Hat …

Type guards in TypeScript

By Nicholas Piano
October 12, 2022

TypeScript has a very rich type system. Sometimes too rich. For example, interfaces and types perform the same function with slightly different syntax.

This post is a short intro to a powerful feature in TypeScript: type guards. This feature also exists in many strongly typed languages. While TypeScript is not strongly typed, it replicates this excellent feature.

The feature

Normally, a function can be annotated with boolean to indicate its return type. However, when the intention is to narrow the type of object being tested from a supertype to one of its subtypes, the annotation parameterName is Type can be used instead. This allows the compiler to infer the type of the argument at other points in the code after the test has been passed.

The following code demonstrates a use of this feature:

type Animal = {
  canWoof: boolean;
};

type Dog = {
  canWoof: true;
  woof: () => void;
};

const isDog = (animal: Animal): animal is Dog => {
  if (animal.canWoof) {
    return true;
  }

  return false;
};

In this example, Animal is a supertype of Dog. The function isDog() takes an Animal object and uses a simple test to determine whether the object satisfies the type Dog. If the …

Integrating Contentful with NuxtJS

By Juan Pablo Ventoso
October 7, 2022

Some time ago, I had the opportunity to collaborate on a cool NuxtJS project. I’m still somewhat new to Vue.js and its related frameworks, meaning I’m discovering exciting new tools and third-party services that can be integrated with them every time a new requirement appears. And there is a particular concept that I heard of, but never worked with until this project: using a Headless CMS to deliver content.

Essentially, a headless CMS permits creating a custom content model, making it accessible through one (or several) APIs that we can query, allowing us to choose whatever presentation layer we prefer to handle the display. This approach decouples the content management part (the “body”) of a project from the design, templates, and frontend logic (the “head”), becoming particularly useful when we have several application types that will interact with the same data, such as a website, a mobile app, or an IoT device.

With that in mind, let’s have a quick look at Contentful: It’s a headless CMS that is offered under the concept of content-as-a-service (CaaS), meaning the content is delivered on demand from a cloud platform to the …

Kubernetes From The Ground Up With AWS EC2

By Jeffry Johar
October 6, 2022

Photo by Darry Lin

One way to learn Kubernetes infrastructure is to build it from scratch. This way of learning was introduced by the founding father of Kubernetes himself: Mr. Kelsey Hightower. The lesson is known as “Kubernetes The Hard Way”.

For this blog entry I would like to take a less demanding approach than Kubernetes The Hard Way, while still being educational. I would like to highlight only the major steps in creating a Kubernetes cluster and what is covered in CKA (Certified Kubernetes Administrator) exams. Thus we are going to use the kubeadm tools to build the Kubernetes cluster.

The steps of creating a Kubernetes cluster are hidden to you if you are using a Kubernetes as a service such as AWS EKS, GCP GKE or the enterprise suites of Kubernetes such as Red Hat Openshift or VMware Tanzu. All of these products let you use Kubernetes without the need to worry about creating it.

Prerequisites

For this tutorial we will need the following from AWS:

• An active AWS account
• EC2 instances with Amazon Linux 2 as the OS
• AWS Keys for SSH to access control node and managed nodes
• Security group which allows SSH and HTTP
• A decent editor such as Vim or Notepad++ to create the …