Introduction to Kubernetes

What is Kubernetes?

• Open-source container orchestration platform.
• Automates deployment, scaling, and management of containerized applications.
• Originated from Google's internal system, Borg.
• Open-sourced by Google in 2014.

Why is it called k8s?

• Abbreviation method: 'k' + 8 letters + 's' (Kubernetes).
• Similar abbreviations: i18n (internationalization), l10n (localization).

Kubernetes Cluster Components

Core Pieces

1. Control Plane: Manages the state of the cluster.
   • Runs on multiple nodes across data center zones in production.
2. Worker Nodes: Run containerized application workloads.

Control Plane Components

• API Server: Primary interface, exposes a RESTful API.
• etcd: Distributed key-value store for cluster's persistent state.
• Scheduler: Schedules pods on worker nodes based on resource needs.
• Controller Manager: Runs controllers to manage state, e.g., replication controller and deployment controller.

Worker Node Components

• Kubelet: Communicates with the control plane, maintains pod states.
• Container Runtime: Manages containers (pulling images, starting/stopping containers).
• Kube-Proxy: Network proxy, routes traffic, provides load balancing across pods.

When to Use Kubernetes?

Advantages

• Scalability & Availability: Self-healing, auto rollbacks, horizontal scaling.
• Portability: Consistent deployment regardless of infrastructure. Runs on-premise, public/hybrid cloud.

Disadvantages

• Complexity: High setup and operational complexity, requires expertise.
• Cost: Resource-intensive; may be overkill for smaller organizations.

Managed Kubernetes Services

• Examples: Amazon EKS, GKE on Google Cloud, AKS on Azure.
• Benefits: Offloads control plane management & maintenance, suitable for mid-sized organizations.
• Smaller Organizations: Often do not need Kubernetes (YAGNI - You ain’t gonna need it).

Conclusion

• Kubernetes is powerful but complex.
• Consider managed services for easier adoption.
• Suitable for scalable, portable containerized applications.

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