containerization

name	containerization
description	Docker, Kubernetes, container orchestration, and cloud-native deployment for data applications
sasmp_version	1.3.0
bonded_agent	03-devops-engineer
bond_type	PRIMARY_BOND
skill_version	2.0.0
last_updated	2025-01
complexity	intermediate
estimated_mastery_hours	120
prerequisites	["python-programming","cloud-platforms"]
unlocks	["mlops","big-data"]

Containerization & Kubernetes

Production-grade container orchestration for data engineering workloads with Docker and Kubernetes.

Quick Start

# Dockerfile for PySpark data application
FROM python:3.12-slim

# Install Java for Spark
RUN apt-get update && apt-get install -y openjdk-17-jdk-headless && \
    apt-get clean && rm -rf /var/lib/apt/lists/*

WORKDIR /app

# Install dependencies first (cache optimization)
COPY requirements.txt .
RUN pip install --no-cache-dir -r requirements.txt

# Copy application code
COPY src/ ./src/
COPY config/ ./config/

# Non-root user for security
RUN useradd -m appuser && chown -R appuser:appuser /app
USER appuser

ENV PYTHONPATH=/app
ENV JAVA_HOME=/usr/lib/jvm/java-17-openjdk-amd64

ENTRYPOINT ["python", "-m", "src.main"]

Core Concepts

1. Multi-Stage Builds

# Build stage
FROM python:3.12 AS builder

WORKDIR /build
COPY requirements.txt .
RUN pip wheel --no-cache-dir --wheel-dir /wheels -r requirements.txt

# Runtime stage
FROM python:3.12-slim AS runtime

COPY --from=builder /wheels /wheels
RUN pip install --no-cache-dir /wheels/* && rm -rf /wheels

COPY src/ /app/src/
WORKDIR /app

USER 1000
CMD ["python", "-m", "src.main"]

2. Kubernetes Deployment

# deployment.yaml
apiVersion: apps/v1
kind: Deployment
metadata:
  name: etl-worker
  labels:
    app: etl-worker
spec:
  replicas: 3
  selector:
    matchLabels:
      app: etl-worker
  template:
    metadata:
      labels:
        app: etl-worker
    spec:
      containers:
      - name: etl-worker
        image: company/etl-worker:v1.2.0
        resources:
          requests:
            memory: "512Mi"
            cpu: "500m"
          limits:
            memory: "2Gi"
            cpu: "2000m"
        env:
        - name: DATABASE_URL
          valueFrom:
            secretKeyRef:
              name: db-credentials
              key: url
        - name: LOG_LEVEL
          value: "INFO"
        livenessProbe:
          httpGet:
            path: /health
            port: 8080
          initialDelaySeconds: 30
          periodSeconds: 10
        readinessProbe:
          httpGet:
            path: /ready
            port: 8080
          initialDelaySeconds: 5
          periodSeconds: 5
      affinity:
        podAntiAffinity:
          preferredDuringSchedulingIgnoredDuringExecution:
          - weight: 100
            podAffinityTerm:
              labelSelector:
                matchLabels:
                  app: etl-worker
              topologyKey: kubernetes.io/hostname

3. Kubernetes CronJob for ETL

# cronjob.yaml
apiVersion: batch/v1
kind: CronJob
metadata:
  name: daily-etl
spec:
  schedule: "0 2 * * *"  # 2 AM daily
  concurrencyPolicy: Forbid
  successfulJobsHistoryLimit: 3
  failedJobsHistoryLimit: 3
  jobTemplate:
    spec:
      backoffLimit: 2
      activeDeadlineSeconds: 7200  # 2 hour timeout
      template:
        spec:
          restartPolicy: Never
          containers:
          - name: etl-job
            image: company/etl-pipeline:v1.0.0
            resources:
              requests:
                memory: "4Gi"
                cpu: "2000m"
              limits:
                memory: "8Gi"
                cpu: "4000m"
            env:
            - name: EXECUTION_DATE
              value: "{{ .Date }}"
            volumeMounts:
            - name: config
              mountPath: /app/config
              readOnly: true
          volumes:
          - name: config
            configMap:
              name: etl-config

4. Helm Chart Structure

# Chart.yaml
apiVersion: v2
name: data-pipeline
version: 1.0.0
appVersion: "2.0.0"
description: Data pipeline Helm chart

# values.yaml
replicaCount: 3

image:
  repository: company/data-pipeline
  tag: "latest"
  pullPolicy: IfNotPresent

resources:
  requests:
    memory: "1Gi"
    cpu: "500m"
  limits:
    memory: "4Gi"
    cpu: "2000m"

autoscaling:
  enabled: true
  minReplicas: 2
  maxReplicas: 10
  targetCPUUtilizationPercentage: 70

env:
  LOG_LEVEL: INFO
  BATCH_SIZE: "1000"

secrets:
  - name: DATABASE_URL
    secretName: db-credentials
    key: url

5. Docker Compose for Local Dev

# docker-compose.yml
version: '3.8'

services:
  postgres:
    image: postgres:16-alpine
    environment:
      POSTGRES_DB: datawarehouse
      POSTGRES_USER: admin
      POSTGRES_PASSWORD: ${DB_PASSWORD}
    ports:
      - "5432:5432"
    volumes:
      - postgres_data:/var/lib/postgresql/data
    healthcheck:
      test: ["CMD-SHELL", "pg_isready -U admin"]
      interval: 5s
      timeout: 5s
      retries: 5

  redis:
    image: redis:7-alpine
    ports:
      - "6379:6379"

  airflow-webserver:
    image: apache/airflow:2.8.0-python3.11
    depends_on:
      postgres:
        condition: service_healthy
      redis:
        condition: service_started
    environment:
      AIRFLOW__CORE__EXECUTOR: CeleryExecutor
      AIRFLOW__DATABASE__SQL_ALCHEMY_CONN: postgresql+psycopg2://admin:${DB_PASSWORD}@postgres/datawarehouse
      AIRFLOW__CELERY__BROKER_URL: redis://redis:6379/0
    ports:
      - "8080:8080"
    volumes:
      - ./dags:/opt/airflow/dags
      - ./plugins:/opt/airflow/plugins

volumes:
  postgres_data:

Tools & Technologies

Tool	Purpose	Version (2025)
Docker	Containerization	25+
Kubernetes	Orchestration	1.29+
Helm	K8s package manager	3.14+
ArgoCD	GitOps deployment	2.10+
Kustomize	K8s config management	Built-in
containerd	Container runtime	1.7+
Podman	Docker alternative	4.8+

Troubleshooting Guide

Issue	Symptoms	Root Cause	Fix
OOMKilled	Pod restarts, exit code 137	Memory limit exceeded	Increase limits, optimize code
CrashLoopBackOff	Pod keeps restarting	App crash, bad config	Check logs: kubectl logs pod
ImagePullBackOff	Pod stuck in Pending	Image not found, auth	Check image name, pull secrets
Pending Pod	Pod won't schedule	No resources, node selector	Check resources, affinity rules

Debug Commands

# Check pod status and events
kubectl describe pod <pod-name>

# View container logs
kubectl logs <pod-name> -c <container-name> --previous

# Execute shell in container
kubectl exec -it <pod-name> -- /bin/sh

# Check resource usage
kubectl top pods

# Debug networking
kubectl run debug --image=busybox -it --rm -- sh

Best Practices

# ✅ DO: Use specific image tags
FROM python:3.12.1-slim

# ✅ DO: Use non-root user
USER 1000

# ✅ DO: Use multi-stage builds
# ✅ DO: Set resource limits
# ✅ DO: Use health checks

# ❌ DON'T: Run as root
# ❌ DON'T: Use latest tag
# ❌ DON'T: Store secrets in images

Resources

• Docker Best Practices
• Kubernetes Docs
• Helm Charts

---

Skill Certification Checklist:

• Can write production Dockerfiles
• Can deploy applications to Kubernetes
• Can create Helm charts
• Can debug container issues
• Can implement health checks and probes