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1. Intro to K8s2. Getting Started Kind3. Getting Started Minikube4. K8s Architecture5. Core Concepts6. Service Discovery7. Storage Orchestration8. Rollouts & Rollbacks9. Self-Healing10. Config & Secrets11. Resource Management12. Advanced Features13. K8s Networking14. Security Practices15. CRDs16. Helm & Packages17. Observability18. Scaling Apps19. K8s API & Clients20. Multi-Tenancy21. Cost Optimization22. Disaster Recovery
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Satya Prakash Nigam
Dec 05, 2024
🚢📦🖥️ Lesson 4: Kubernetes Architecture

Introduction

Kubernetes is a powerful container orchestration platform designed to manage containerized applications at scale. Its architecture is composed of a control plane and nodes. Understanding its architecture is crucial for effectively managing and troubleshooting your Kubernetes clusters. This lesson will explore the key components of Kubernetes architecture, including the Control Plane, Node components, and the interaction between these elements.

The Control Plane

The Control Plane is responsible for managing the state of the Kubernetes cluster. It makes global decisions about the cluster (e.g., scheduling), and it detects and responds to cluster events (e.g., starting up a new pod when a deployment’s replicas field is unsatisfied). The main components of the Control Plane include:

Component
Role
Functions
API Server (kube-apiserver) The API Server is the central management entity that exposes the Kubernetes API. It is the entry point for all administrative tasks within the cluster.
  • Authentication and Authorization: Validates and processes incoming API requests, authenticating users and authorizing their actions.
  • Data Persistence: Ensures all state information and configuration data are securely stored in etcd.
  • Communication: Acts as the primary interface for communication between various components of the control plane and the nodes.
Etcd Etcd is a distributed, consistent, and highly-available key-value store used as Kubernetes' backing store for all cluster data.
  • Data Storage: Stores configuration data, state information, and metadata for the cluster.
  • Consistency: Ensures that all data is replicated and consistent across all etcd instances in the cluster.
  • High Availability: Designed to handle network partitions and tolerate node failures.
Controller Manager (kube-controller-manager) The Controller Manager runs various controllers that regulate the state of the cluster.
  • Node Controller: Monitors the health of nodes and takes action if nodes go down.
  • Replication Controller: Ensures the desired number of pod replicas are running.
  • Endpoints Controller: Manages the mapping between services and pods.
  • Service Account Controller: Manages service accounts and tokens for accessing the API.
Scheduler (kube-scheduler) The Scheduler is responsible for assigning newly created pods to nodes within the cluster.
  • Resource Allocation: Evaluates the current state of the cluster and schedules pods based on resource requirements, constraints, and policies.
  • Scheduling Policies: Considers factors like resource availability, affinity/anti-affinity rules, taints, tolerations, and more to make scheduling decisions.

Node Components

A Node is a worker machine in Kubernetes, formerly known as a minion. Nodes run the pods, which are the smallest deployable units in Kubernetes. Each node contains the necessary components to run pods:

Component
Role
Functions
Kubelet The Kubelet is the primary 'node agent' that runs on each Node.
  • Pod Lifecycle Management: Starts, stops, and monitors containers as specified by pod definitions.
  • Health Checks: Performs health checks on pods and reports status to the kube-apiserver.
  • Configuration: Reads pod specifications from the API server and ensures the pods are running as described.
Kube-proxy Kube-proxy manages network communication for the nodes in the cluster.
  • Network Routing: Implements network routing rules to ensure that each node can communicate with each other.
  • Load Balancing: Provides load balancing for service traffic.
  • IP Translation: Manages IP address translation to route traffic correctly within the cluster.
Container Runtime The container runtime is responsible for running containers on each node.
  • Container Management: Ensures that containers are created, started, stopped, and removed as needed.
  • Integration: Interfaces with Kubernetes to receive instructions and report the status of containers.
  • Examples: Docker, containerd, CRI-O, and others.

Additional Components

Component
Role
Function
DNS (CoreDNS) DNS is a built-in Kubernetes service that provides name resolution within the cluster. It translates service names to IP addresses, allowing pods and services to communicate with each other using human-readable names.
Ingress Controller An Ingress Controller manages Ingress resources. It provides HTTP and HTTPS routing to services based on rules defined in Ingress resources, allowing external users to access services within the cluster.

Interactions Between Components

Interactions between the components include:

  • API Requests: Users interact with the cluster through the Kubernetes API Server. The API Server processes requests and updates the etcd store with the desired state.
  • State Synchronization: The Controller Manager monitors the current state of the cluster, as recorded in etcd, and makes adjustments to move towards the desired state.
  • Scheduling: The Scheduler assigns pods to nodes based on resource availability and policies, updating the state in etcd.
  • Node Management: Kubelet ensures that containers are running as specified. Kube-proxy maintains network rules, and the container runtime runs the containers.

Summary

The control plane and nodes work together to form a resilient and scalable infrastructure for managing containerized applications. The control plane maintains the cluster state, while the nodes run the applications. Key components like kube-apiserver, etcd, kube-scheduler, kube-controller-manager, kubelet, and kube-proxy ensure seamless operation and orchestration. Understanding the roles and interactions of these core components is essential for effective cluster management and troubleshooting. By mastering these architectural elements, you'll be well-equipped to harness the full power of Kubernetes in your deployments.

Key Takeaways

#
Key Takeaway
1
 Kubernetes architecture is composed of a control plane and nodes, designed to manage containerized applications at scale.
2
 The Control Plane manages the overall state of the cluster, handling scheduling, state regulation, and cluster events.
3
 Key components of the Control Plane include the API Server, Etcd, Controller Manager, and Scheduler.
4
 Nodes are worker machines that run the pods and are managed by components like Kubelet, Kube-proxy, and the Container Runtime.
5
 Additional components like DNS (CoreDNS) and Ingress Controllers play crucial roles in name resolution and external access.
6
 Understanding the interactions between components is essential for effective cluster management and troubleshooting.
7
 Mastering Kubernetes architecture allows for effective deployment, scaling, and management of containerized applications.
Kubernetes - From Zero to Hero

Q&A for Interview Prep

Here are 10 pairs of short Q&A based on the shared Kubernetes Lesson 3 text:

#
Question
Answer
1
 What are the two main components of Kubernetes architecture? The Control Plane and Nodes.
2
 What is the primary role of the Control Plane in Kubernetes? The Control Plane manages the state of the Kubernetes cluster, makes global decisions, and detects/responds to cluster events.
3
 What is the role of the API Server in Kubernetes? The API Server acts as the central management entity, exposing the Kubernetes API for cluster operations.
4
 Where does Kubernetes store its configuration data and cluster state? In etcd, a distributed, consistent, and highly-available key-value store.
5
 Which component is responsible for scheduling pods to nodes? The Scheduler (kube-scheduler).
6
 What is the main function of the Kubelet on a node? The Kubelet manages pod lifecycles, health checks, and ensures the pods run as defined in the specifications.
7
 How does Kube-proxy contribute to network communication in a Kubernetes cluster? It manages network routing, load balancing, and IP translation for nodes in the cluster.
8
 What is CoreDNS used for in a Kubernetes cluster? CoreDNS provides name resolution, translating service names to IP addresses for internal communication.
9
 What is the purpose of the Ingress Controller? The Ingress Controller manages HTTP/HTTPS routing for external access to services within the cluster.
10
 How do the Control Plane and Nodes interact in Kubernetes? The Control Plane maintains the desired state of the cluster, while Nodes execute and manage the pods as instructed by the Control Plane.

Explore the contents of the other lectures - by click a lecture.

Lectures:

S No
Lecture
Topics
1
 Introduction to Kubernetes Overview, Concepts, Benefits
2
 Getting Started with K8s + Kind Installation, Configuration, Basic Commands
3
 Getting Started with K8s + Minikube Installation, Configuration, Basic Commands
4
 Kubernetes Architecture Control Plane, Nodes, Components
5
 Core Concepts Pods, ReplicaSets, Deployments
6
 Service Discovery and Load Balancing Services, Endpoints, Ingress
7
 Storage Orchestration Persistent Volumes, Persistent Volume Claims, Storage Classes
8
 Automated Rollouts and Rollbacks Deployment Strategies, Rolling Updates, Rollbacks
9
 Self-Healing Mechanisms Probes, Replication, Autoscaling
10
 Configuration and Secret Management ConfigMaps, Secrets
11
 Resource Management Resource Quotas, Limits, Requests
12
 Advanced Features and Use Cases DaemonSets, StatefulSets, Jobs, CronJobs
13
 Networking in Kubernetes Network Policies, Service Mesh, CNI Plugins
14
 Security Best Practices RBAC, Network Policies, Pod Security Policies
15
 Custom Resource Definitions (CRDs) Creating CRDs, Managing CRDs
16
 Helm and Package Management Helm Charts, Repositories, Deploying Applications
17
 Observability and Monitoring Metrics Server, Prometheus, Grafana
18
 Scaling Applications Horizontal Pod Autoscaling, Vertical Pod Autoscaling
19
 Kubernetes API and Clients kubectl, Client Libraries, Custom Controllers
20
 Multi-Tenancy and Cluster Federation Namespaces, Resource Isolation, Federation V2
21
 Cost Optimization Resource Efficiency, Cost Management Tools
22
 Disaster Recovery and Backups Backup Strategies, Tools, Best Practices
Prompt Engineering
In the dynamic world of containers, Kubernetes is the captain that navigates through the seas of scale, steering us towards efficiency and innovation.😊✨ - The Alchemist "
GitHub Link: 
Tags:
  • Kubernetes
  • K8s
  • Container Orchestration
  • Cloud Native
  • Docker
  • kubectl
  • Kubernetes Architecture
  • Control Plane
  • Nodes
  • Services
  • Pods
  • ReplicaSets
  • Deployments
  • Service Discovery
  • Load Balancing
  • Storage Orchestration
  • Persistent Volumes
  • Volume Claims
  • Storage Classes
  • Rollouts
  • Rollbacks
  • Self-Healing
  • ConfigMaps
  • Secrets
  • Resource Management
  • Quotas
  • Limits
  • Advanced Features
  • Networking
  • RBAC
  • Network Policies
  • Pod Security
  • CRDs
  • Helm
  • Monitoring
  • Prometheus
  • Grafana
  • Scaling
  • API Clients
  • Multi-Tenancy
  • Cluster Federation
  • Cost Optimization
  • Disaster Recovery
  • Backups
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Last Updated: December 30, 2024 16:40:29

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