Container Orchestration

Also Known As

TL;DR

Explanation

Kubernetes (K8s) manages containerised workloads: Pods (one or more containers), Deployments (desired replica count), Services (stable network endpoint), Ingress (HTTP routing), ConfigMaps/Secrets (configuration), and PersistentVolumes (storage). The control plane schedules and monitors; worker nodes run containers. Key operations: rolling updates, health checks, automatic restarts, horizontal pod autoscaling. For PHP: PHP-FPM runs in containers behind an nginx sidecar, scaled by HPA based on CPU or request rate.

Diagram

flowchart TD
    subgraph Kubernetes Cluster
        API[API Server]
        subgraph Node 1
            P1[Pod: PHP-FPM]
            P2[Pod: Worker]
        end
        subgraph Node 2
            P3[Pod: PHP-FPM]
            P4[Pod: Nginx]
        end
    end
    SVC[Service - stable DNS] --> P1 & P3
    ING[Ingress - routes traffic] --> SVC
    HPA[HPA - auto-scales pods<br/>on CPU or custom metrics] --> P1 & P3
    CM[ConfigMap - env config] -.-> P1 & P2 & P3
    SEC[Secret - credentials] -.-> P1 & P2 & P3
style ING fill:#d29922,color:#fff
style HPA fill:#238636,color:#fff
style SVC fill:#1f6feb,color:#fff

Common Misconception

Why It Matters

Common Mistakes

• Running a database in Kubernetes without understanding persistent storage — container restarts lose data without PVCs.
• Not setting resource requests and limits — containers without limits steal CPU/memory from neighbours.
• Not implementing readiness and liveness probes — Kubernetes cannot route traffic away from broken pods without them.
• Storing secrets in ConfigMaps — use Kubernetes Secrets or an external secrets manager.

Code Examples

# Deployment without resource limits or health probes:
apiVersion: apps/v1
kind: Deployment
spec:
  template:
    spec:
      containers:
      - name: php-fpm
        image: myapp:latest
        # No resources: limits — can consume all node CPU/memory
        # No readinessProbe — traffic sent to broken pods
        # No livenessProbe — dead pods never restarted

spec:
  containers:
  - name: php-fpm
    image: myapp:1.2.3  # Pinned version, not 'latest'
    resources:
      requests: { cpu: 250m, memory: 256Mi }
      limits:   { cpu: 500m, memory: 512Mi }
    readinessProbe:
      httpGet: { path: /health, port: 80 }
      initialDelaySeconds: 5
    livenessProbe:
      httpGet: { path: /ping, port: 80 }
      periodSeconds: 10

References

• ↗ https://kubernetes.io/docs/concepts/

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