What is Kubernetes and why Kubernetes is used

What is kubernetes and what kubernetes is used for. K8s container, pod, service, deployments and ingress explained with real example with docker containers.

Why Kubernetes is used?

Kubernetes is used to automate the deployment, scaling, and management of containerized applications. It provides a platform-agnostic way to manage containers, allowing developers to focus on writing code, while Kubernetes handles tasks such as scaling, rolling updates, and resource management.

Kubernetes also provides resiliency through features such as self-healing and auto-replacement of failed containers. This helps ensure applications are highly available and can withstand failures, making it an essential tool for modern cloud-native application development and deployment.

Kubernetes: Deployment and Management - How Kubernetes can be used to host microservices?

Kubernetes can be used to host microservices by providing a way to manage and deploy individual components of a larger application as separate, independently deployable services. With Kubernetes, microservices can be packaged as containers, which can be easily spun up and scaled as needed. Kubernetes also provides a centralized management and networking solution for microservices, allowing for easy communication between services and automatic load balancing.

Additionally, Kubernetes' self-healing and auto-replacement capabilities ensure high availability of the microservices, reducing downtime and allowing for a more robust overall application. By using Kubernetes to host microservices, organizations can achieve improved scalability, resilience, and ease of management compared to traditional monolithic application architectures.

What is a container in Kubernetes

In Kubernetes, a container is a lightweight, stand-alone, and executable software package that includes everything needed to run a piece of software, including the code, runtime, system tools, libraries, and settings. Containers provide a consistent and predictable environment for applications to run in, regardless of the underlying infrastructure.

This makes it easy to deploy, run, and manage applications in different environments, such as on-premises, in the cloud, or on a developer's laptop.

In the context of Kubernetes, containers are used to package applications and their dependencies as units that can be easily deployed and managed as part of a larger application. Containers are run in pods, which are the smallest and simplest unit in the Kubernetes object model, and provide an isolated environment for running one or more containers. Pods are the fundamental building blocks for creating and managing applications on a Kubernetes cluster.

Here is an example of a pod definition in YAML format:

apiVersion: v1
kind: Pod
metadata:
  name: myapp-pod
  labels:
    app: myapp
spec:
  containers:
  - name: myapp-container
    image: myapp:1.0
    ports:
    - containerPort: 80
  

In this example, the pod is named myapp-pod and has a label of app: myapp. The pod definition includes a single container named myapp-container that is using the image myapp:1.0. The container has one port exposed, which is port 80. This pod definition can be used to create a single instance of the myapp-container in a Kubernetes cluster.

What is a Kubernetes pod?

A pod in Kubernetes is the smallest and simplest unit in the Kubernetes object model and represents a single instance of a running process in a cluster. Pods provide an isolated environment for running one or more containers, and all containers in a pod share the same network namespace, allowing them to easily communicate with each other.

Here is an example of a pod definition in YAML format:

apiVersion: v1 
kind: Pod 
metadata: 
name: myapp-pod 
labels: 
  app: myapp 
spec: 
  containers: 
    - name: myapp-container 
        image: myapp:1.0 
        ports: 
          - containerPort: 80 
  

What is a Kubernetes deployment?

A deployment in Kubernetes is a higher-level abstraction that provides a declarative way to manage the desired state of an application and its components. A deployment ensures that a specified number of replicas of a pod are running and available at all times, and provides a way to perform updates to the application, such as rolling updates or rollbacks, without downtime.

Here's an example of deployment definition

apiVersion: apps/v1
kind: Deployment
metadata:
  name: myapp-deployment
spec:
  replicas: 3
  selector:
    matchLabels:
      app: myapp
  template:
    metadata:
      labels:
        app: myapp
    spec:
      containers:
      - name: myapp-container
        image: myapp:1.0
        ports:
        - containerPort: 80
  

In this example, the deployment is named myapp-deployment and is defined to manage pods with the label app: myapp. The deployment ensures that there are 3 replicas of the pod running at all times, as specified by the replicas field. The pod template defines the desired state of the pod, including the container image and exposed port. This deployment definition can be used to create and manage multiple instances of the myapp-container in a Kubernetes cluster.

What is a Kubernetes service compare it with deployment?

A Kubernetes service is a high-level abstraction that defines a logical set of pods and a policy by which to access them. A service provides stable network endpoints for pods, allowing other components in the cluster to access the pods without having to know the underlying network details or the individual pod IP addresses.

In comparison, a deployment is a higher-level abstraction that provides a declarative way to manage the desired state of an application and its components. A deployment ensures that a specified number of replicas of a pod are running and available at all times, and provides a way to perform updates to the application, such as rolling updates or rollbacks, without downtime.

While both services and deployments are essential components of a Kubernetes application, they serve different purposes and provide different functionality. Services provide network access to pods, while deployments manage the desired state and availability of pods. In practice, services and deployments are often used together to provide a complete and robust application environment in a Kubernetes cluster.

What is ingress in Kubernetes?

In Kubernetes, an ingress is a collection of rules that allow inbound connections to reach the cluster services. It provides a way to route external traffic to one or more services in the cluster, based on the request URL path or host name.

An ingress is typically associated with a Kubernetes service, which acts as a target for the ingress traffic. The service selects a set of pods to receive traffic, based on its selector, and the ingress routes traffic to the selected pods.

Here is an example of an ingress definition in YAML format, associated with a service:

apiVersion: networking.k8s.io/v1
kind: Ingress
metadata:
  name: myapp-ingress
spec:
  rules:
  - host: myapp.example.com
    http:
      paths:
      - path: /myapp
        pathType: Prefix
        backend:
          service:
            name: myapp-service
            port:
              name: http
  

In this example, the ingress is named myapp-ingress and has a single rule that routes traffic to the myapp-service service, based on the host name myapp.example.com and the URL path /myapp. The service is configured to use the http port. This ingress definition can be used to route external traffic to the myapp-service service in a Kubernetes cluster.

What is a node in Kubernetes?

In Kubernetes, a node is a worker machine in a cluster that runs one or more pods. Each node runs a container runtime, such as Docker or CRI-O, to manage and run the containers that make up the pods. Nodes also run the Kubernetes kubelet component, which communicates with the control plane and ensures that the desired state of the pods is maintained.

Nodes are managed by the Kubernetes control plane components, such as the master node and the API server. The control plane components use the node information to schedule pods to run on the nodes, to manage the network communication between pods, and to enforce resource constraints, such as CPU and memory limits.

In a typical Kubernetes cluster, there are multiple nodes, each running a set of pods. This allows for horizontal scaling and redundancy, so that if one node fails, the pods running on it can be rescheduled to run on another node. Nodes can also be added or removed from the cluster as needed to meet changing resource demands.

When should Kubernetes be introduced in projects an what kind of engineering projects it can be effective/non effective?

Kubernetes can be a valuable tool for many engineering projects, but it is not suitable for every project. When deciding whether to use Kubernetes in a project, several factors should be considered, including the size and complexity of the project, the desired level of automation and scalability, and the existing infrastructure and tools.

Kubernetes is particularly effective for projects that involve multiple, complex microservices, where there is a need for high availability, scalability, and automation. For example, Kubernetes can be used to manage large-scale, multi-tier applications, such as web applications, databases, and distributed systems.

Kubernetes is also useful for projects that need to run in a hybrid or multi-cloud environment, as it provides a common platform for managing containers across different cloud providers or on-premises environments.

However, Kubernetes may not be the best choice for smaller projects, or projects that have simple requirements and do not need the features provided by Kubernetes. Additionally, Kubernetes can have a high learning curve and may require significant effort to set up and manage, so projects with limited resources or tight timelines may not be suitable for Kubernetes.

In summary, Kubernetes is a powerful tool for managing large and complex engineering projects, but it may not be necessary or appropriate for every project. The specific needs and requirements of each project should be evaluated before deciding whether to use Kubernetes.