Chapter 06: Orchestration (The Captain)

"It works on my machine" is not a valid excuse.

You have 3 services now:

1. Gopher Shop (Web + API)
2. Postgres (DB)
3. GoTracker (Microservice)
4. Redis (Cache)
5. Kafka (Broker)

Starting them manually (5 terminal windows) is madness.

1. Docker Compose (The Local Conductor)

We define the whole orchestra in one file: docker-compose.yml.

services:
  shop:
    build: ./gopher-shop
    ports: ["8080:8080"]
    depends_on: [postgres, kafka]
  
  tracker:
    build: ./go-tracker
    depends_on: [redis, kafka]

  postgres:
    image: postgres:15
  
  redis:
    image: redis:7
    
  kafka:
    image: bitnami/kafka:latest

Command: docker-compose up. Result: The whole city starts up.

2. Kubernetes (The Container Ship) 🚢

When you go to production (AWS, Google Cloud), you use Kubernetes (K8s). K8s is like Docker Compose, but across 100 servers.

• Pod: A small group of containers (e.g., 1 Shop instance).
• Deployment: "I want 3 replicas of the Shop."
• Service: "Give me a Load Balancer IP to talk to the Shop."

3. Visual Signal (The Container Ship) ⚓

Concept: Container Orchestration. Signal: A Captain managing a massive ship.

• Containers: The standard metal boxes.
• Docker: The crane that lifts them.
• Kubernetes: The Captain who decides where each box goes to balance the ship.

4. Final Words on Ops

As a Backend Engineer, you don't need to be a DevOps expert. But you MUST understand how your code runs.

• How do I view logs? (kubectl logs)
• How do I restart it? (kubectl rollout restart)
• How do I scale it? (kubectl scale --replicas=5)