AKS From Zero To Hero - Part 1

Let's start with the definition of Kubernetes, so what is Kubernnetes (K8S), kubernetes is an open source container orchestration framework which was originally developed by google

• Extensible
• Portable
  
• Managing containerized workloads and services, that facilitates both declarative configuration and automation.
• It manages containers (be docker containers, or from some other technology)

Which basically means that, kubernetes helps you manage applications that are made up of hundreds or maybe thousands of containers and it helps you manage them in different environments like physical machines, virtual machines or cloud environments or even hybrid deployment environments.

Why K8s?

• Standardized API for infrastructure abstraction: You don’t need to worry about provisioning extra resources or clouds services like public ip addresses or load balancers
  
• Self Healing : Kubernetes gives us out of the box self healing of applications through deployments and other technologies that allows us to handle failures of computer or application resources
  
• Scalability: Kubernetes gives us the underlying technologies to scale not only our applications but also our cluster to handle business needs as workloads come in
  
• Extensibility: allow you to develop your own extensions if not there is a vibrant ecosystem building extension that you can take advantage of
  

Kubernetes is a cluster-based orchestrator, hence instead of having a single machine, it uses several machines working as one. These are called nodes. Can be virtual or physical machine

In K8s cluster we will find two types of nodes:

1. Worker Nodes:  Workloads are deployed on these nodes.
2. Master Nodes:  Manages the worker nodes and the Pods in the cluster
   

Node Componentes:

Master Node:

• API Server: The entryPoint to the kubernetes cluster, so this is the process which the different Kubernetes clients will talk to like UI if you’re using K8s dashboard or CLI
• Controller Manager:  Keeping Overview or track of what's happening in the cluster, e.g if the container Died and need to be restarted
• Schedular: Responsible for scheduling container on different nodes based on the resource's availability
• ETCD: Key value storage, store the current state of the K8s cluster, hence it has the configuration data inside, and the status for each container/node

Worker Node:

• Kubelet: is actually a kubernetes process that makes it possible for the cluster to talk to each other/to communicate to each other and actually execute some tasks on those nodes like running application processes.
• kube-proxy: maintains network rules on nodes, load balancing, allow network communication to your Pods from network sessions inside or outside of your cluster

How kubernetes Work:

1. Kubernetes admins communicate with API server and apply desired state
2. Master nodes actively enforce desired state on worker nodes
3. Worker nodes support communication between containers
4. Worker nodes support communication from the Internet

So, how to create or manage K8s resources, actually there are multiple ways to achieve that and the easiest way to achieve that is by using the Manifest file (Yaml)

A Kubernetes manifest file allows you to describe your workloads in the YAML format declaratively, also the manifest files contain all the information that's needed to create and manage the described workload. The structure of manifest files differs depending on the type of resource that you create.

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deployment
spec:
  selector:
    matchLabels:
      app: nginx
  replicas: 2
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:1.14.2
        ports:
        - containerPort: 80

What's next?
This was part one of the article. In the next part, we will continue this discussion with K8s services,AKS, etc.
Continue Reading: AKS From Zero To Hero - Part 2