Announcing Tetrate Agent Router Service: Intelligent routing for GenAI developers

Learn more

How Does Kubernetes Work?

How Does Kubernetes Work?

Kubernetes is an open-source container orchestration platform that automates the deployment, scaling, and management of containerized applications. It provides a robust framework for running distributed systems reliably across clusters of machines.

Understanding Kubernetes Architecture

Control Plane Components

The control plane manages the overall cluster state:

kube-apiserver:

  • API Server: Central communication hub for all Kubernetes components
  • REST API: Exposes Kubernetes API for cluster management
  • Authentication: Handles user authentication and authorization
  • Validation: Validates and processes API requests

etcd:

  • Distributed Database: Stores all cluster data and configuration
  • Consistency: Ensures data consistency across the cluster
  • Backup: Critical for cluster backup and disaster recovery
  • High Availability: Can be deployed in HA mode for production

kube-scheduler:

  • Pod Scheduling: Determines where to place new pods
  • Resource Allocation: Considers resource requirements and constraints
  • Affinity Rules: Applies node affinity and anti-affinity rules
  • Load Balancing: Distributes pods across available nodes

kube-controller-manager:

  • Controller Loop: Runs various controllers that maintain cluster state
  • Node Controller: Monitors node health and handles node failures
  • Replication Controller: Maintains desired number of pod replicas
  • Service Controller: Manages service endpoints and load balancing

Node Components

Worker nodes run the actual application workloads:

kubelet:

  • Node Agent: Primary node agent that runs on each node
  • Pod Management: Creates, modifies, and deletes pods
  • Health Monitoring: Monitors pod health and reports to API server
  • Resource Management: Manages node resources and container runtime

kube-proxy:

  • Network Proxy: Maintains network rules and enables communication
  • Service Discovery: Implements service abstraction and load balancing
  • Network Policies: Enforces network policies and security rules
  • IP Tables: Manages IP tables rules for traffic routing

Container Runtime:

  • Container Engine: Runs containers (Docker, containerd, CRI-O)
  • Image Management: Pulls and manages container images
  • Container Lifecycle: Starts, stops, and manages containers
  • Resource Isolation: Provides resource isolation and security

How Kubernetes Manages Applications

Pod Lifecycle

Pods are the smallest deployable units in Kubernetes:

Pod Creation:

  1. API Request: User submits pod creation request to API server
  2. Scheduling: Scheduler determines optimal node for pod placement
  3. Node Assignment: Pod is assigned to specific node
  4. Container Creation: Kubelet creates containers on assigned node
  5. Health Monitoring: Kubelet monitors pod health and reports status

Pod States:

  • Pending: Pod accepted but not yet scheduled or running
  • Running: Pod scheduled and all containers running
  • Succeeded: All containers completed successfully
  • Failed: At least one container failed or terminated
  • Unknown: Pod state cannot be determined

Service Discovery and Load Balancing

Services provide stable networking for applications:

Service Types:

  • ClusterIP: Internal cluster access (default)
  • NodePort: External access via node ports
  • LoadBalancer: Cloud provider load balancer integration
  • ExternalName: DNS-based service discovery

Load Balancing:

  • Round Robin: Distributes requests across available pods
  • Session Affinity: Maintains client session consistency
  • Health Checks: Removes unhealthy pods from load balancer
  • Traffic Splitting: Supports canary deployments and A/B testing

Scaling and Self-Healing

Automatic scaling and recovery capabilities:

Horizontal Pod Autoscaler (HPA):

  • Metrics Monitoring: Monitors CPU, memory, and custom metrics
  • Automatic Scaling: Scales pods based on resource utilization
  • Target Metrics: Maintains target average utilization
  • Scale Limits: Configurable minimum and maximum replicas

Self-Healing:

  • Health Checks: Regular health checks on pods and containers
  • Automatic Restart: Restarts failed containers automatically
  • Node Failure Handling: Reschedules pods from failed nodes
  • Replica Management: Maintains desired number of replicas

Kubernetes Resource Management

Namespaces

Logical isolation within the cluster:

Default Namespaces:

  • default: Default namespace for user resources
  • kube-system: System components and add-ons
  • kube-public: Publicly accessible resources
  • kube-node-lease: Node lease objects

Namespace Benefits:

  • Resource Isolation: Separate resources by project or team
  • Access Control: Different RBAC policies per namespace
  • Resource Quotas: Limit resource consumption per namespace
  • Network Policies: Apply network policies at namespace level

Resource Quotas and Limits

Resource management and constraints:

Resource Quotas:

  • CPU and Memory: Limit total CPU and memory usage
  • Storage: Limit persistent volume claims
  • Object Counts: Limit number of pods, services, etc.
  • Namespace Scope: Applied at namespace level

Resource Limits:

  • Requests: Minimum resources guaranteed to pod
  • Limits: Maximum resources pod can consume
  • Quality of Service: Determines pod scheduling priority
  • OOM Handling: Out-of-memory handling and eviction

Networking in Kubernetes

Pod Networking

Network connectivity between pods:

Pod Network:

  • Unique IP: Each pod gets unique cluster IP address
  • Flat Network: All pods can communicate directly
  • Network Plugins: CNI plugins provide networking implementation
  • Cross-Node Communication: Pods can communicate across nodes

Service Networking:

  • Virtual IP: Services get virtual IP addresses
  • Load Balancing: Distributes traffic across service endpoints
  • DNS Resolution: Automatic DNS resolution for services
  • Port Mapping: Maps service ports to pod ports

Network Policies

Security and traffic control:

Policy Types:

  • Ingress Rules: Control incoming traffic to pods
  • Egress Rules: Control outgoing traffic from pods
  • Namespace Isolation: Isolate traffic between namespaces
  • Pod Selectors: Target specific pods or namespaces

Implementation:

  • Network Plugins: Requires network plugin that supports policies
  • Policy Enforcement: Applied at network level
  • Default Policies: Allow or deny traffic by default
  • Policy Chaining: Multiple policies can be applied

Storage in Kubernetes

Persistent Volumes

Persistent storage for applications:

Volume Types:

  • Local Storage: Node-local storage
  • Network Storage: NFS, iSCSI, cloud storage
  • Cloud Volumes: AWS EBS, Azure Disk, GCP PD
  • Distributed Storage: Ceph, GlusterFS

Volume Lifecycle:

  • Provisioning: Dynamic or static volume provisioning
  • Binding: Binding volumes to persistent volume claims
  • Mounting: Mounting volumes to pods
  • Reclaiming: Volume cleanup after pod deletion

ConfigMaps and Secrets

Configuration and sensitive data management:

ConfigMaps:

  • Configuration Data: Non-sensitive configuration data
  • Environment Variables: Inject configuration as environment variables
  • Files: Mount configuration as files in pods
  • Hot Reloading: Update configuration without pod restart

Secrets:

  • Sensitive Data: Passwords, tokens, certificates
  • Encryption: Encrypted storage in etcd
  • Access Control: RBAC-based access to secrets
  • External Integration: Integration with external secret managers

Security in Kubernetes

Authentication and Authorization

User and service authentication:

Authentication Methods:

  • Client Certificates: X.509 certificates for API access
  • Bearer Tokens: JWT tokens for service accounts
  • OpenID Connect: Integration with identity providers
  • Webhook: Custom authentication webhooks

Authorization:

  • RBAC: Role-based access control
  • ABAC: Attribute-based access control
  • Node Authorization: Node-specific authorization
  • Webhook Authorization: Custom authorization webhooks

Pod Security

Security policies for pods:

Pod Security Standards:

  • Privileged: Unrestricted access (not recommended)
  • Baseline: Minimal security restrictions
  • Restricted: Maximum security restrictions

Security Context:

  • RunAsUser: User ID for running containers
  • RunAsGroup: Group ID for running containers
  • ReadOnlyRootFilesystem: Read-only root filesystem
  • Capabilities: Linux capabilities for containers

Monitoring and Observability

Metrics and Monitoring

Cluster and application monitoring:

Metrics Sources:

  • kubelet: Node and pod metrics
  • kube-state-metrics: Kubernetes object metrics
  • cAdvisor: Container resource metrics
  • Custom Metrics: Application-specific metrics

Monitoring Tools:

  • Prometheus: Metrics collection and storage
  • Grafana: Metrics visualization and dashboards
  • AlertManager: Alerting and notification
  • Custom Dashboards: Application-specific monitoring

Logging

Centralized logging for applications:

Log Collection:

  • Container Logs: Standard output and error streams
  • Node Logs: System and application logs
  • Audit Logs: API server audit logs
  • Event Logs: Kubernetes events

Logging Solutions:

  • Fluentd: Log collection and forwarding
  • Elasticsearch: Log storage and indexing
  • Kibana: Log visualization and search
  • Centralized Logging: Unified logging infrastructure

Best Practices

1. Resource Management

Efficient resource utilization:

  • Resource Requests: Always specify resource requests
  • Resource Limits: Set appropriate resource limits
  • Horizontal Scaling: Use HPA for automatic scaling
  • Resource Quotas: Implement namespace resource quotas

2. Security

Security-first approach:

  • RBAC: Implement role-based access control
  • Network Policies: Use network policies for traffic control
  • Pod Security: Apply pod security standards
  • Secret Management: Use external secret managers

3. Monitoring

Comprehensive monitoring:

  • Health Checks: Implement liveness and readiness probes
  • Metrics Collection: Collect application and infrastructure metrics
  • Logging: Centralized logging for all applications
  • Alerting: Set up alerts for critical issues

4. Backup and Recovery

Disaster recovery planning:

  • etcd Backup: Regular backup of etcd data
  • Application Backup: Backup application data and configurations
  • Recovery Procedures: Document recovery procedures
  • Testing: Regular testing of backup and recovery procedures
Decorative CTA background pattern background background
Tetrate logo in the CTA section Tetrate logo in the CTA section for mobile

Ready to enhance your
network

with more
intelligence?