Getting Started with Kubernetes

We've learned the benefits that containers can bring us, but what if we need to scale out our services for business needs? Is there a way to build services across multiple machines without dealing with cumbersome network and storage settings? Also, is there any other easy way to manage and roll out our microservices by different service cycle? That's how Kubernetes comes into play. In this chapter, we'll learn:

• Kubernetes concept
• Kubernetes components
• Kubernetes resources and their configuration file
• How to launch the kiosk application by Kubernetes

Understanding Kubernetes

Kubernetes is a platform for managing application containers across multiple hosts. It provides lots of management features for container-oriented applications, such as auto scaling, rolling deployment, compute resource, and volume management. Same as the nature of containers, it's designed to run anywhere, so we're able to run it on a bare metal, in our data center, on the public cloud, or even hybrid cloud.

Kubernetes considers most of the operational needs for application containers. The highlights are:

• Container deployment
• Persistent storage
• Container health monitoring
• Compute resource management
• Auto-scaling
• High availability by cluster federation

Kubernetes is a perfect match for microservices. With Kubernetes, we can create a Deployment to rollout, rollover, or roll back selected containers (Chapter 7, Continous Delivery). Containers...

Getting started with Kubernetes

In this section, we will learn how to set up a small single-node cluster at the start. Then we'll get to learn how to interact with Kubernetes via its command-line tool--kubectl. We will go through all the important Kubernetes API objects and their expression in YAML format, which is the input to kubectl, then kubectl will send the request to the API server accordingly.

Preparing the environment

The easiest way to start is running minikube (https://github.com/kubernetes/minikube), which is a tool to run Kubernetes on a single node locally. It supports to run on Windows, Linux, and macOS. In the following example, we'll run on macOS. Minikube will launch a VM with Kubernetes installed...

Multi-containers orchestration

In this section, we'll revisit our ticketing service: a kiosk web service as frontend, providing interface for get/put tickets. There is a Redis acting as cache, to manage how many tickets we have. Redis also acts as a publisher/subscriber channel. Once a ticket is sold, kiosk will publish an event into it. Subscriber is called recorder, which will write a timestamp and record it to the MySQL database. Please refer to the last section in Chapter 2, DevOps with Container for the detailed Dockerfile and Docker compose implementation. We'll use Deployment, Service, Secret, Volume, and ConfigMap objects to implement this example in Kubernetes. Source code can be found at https://github.com/DevOps-with-Kubernetes/examples/tree/master/chapter3/3-3_kiosk.

An example of kiosk in Kubernetes world

We'll need four kinds of pods. Deployment is...

Summary

In this chapter, we learned the basic concept of Kubernetes. We learned Kubernetes master has kube-apiserver to handle the requests, and controller managers are the control center of Kubernetes, for example, it ensures our desired container amount is fulfilled, controls the endpoint to associate pods and services, and controls API access token. We also have Kubernetes nodes, which are the workers to host the containers, receive the information from master, and route the traffic based on the configuration.

We then used minikube to demonstrate basic Kubernetes objects, including pod, ReplicaSets, ReplicationControllers, deployments, services, secrets, and ConfigMap. In the end, we demonstrated how to combine all the concepts we've learned into kiosk application deployment.

As we mentioned previously, the data inside containers will be gone when a container is gone....