---
gsd_summary_version: 1.0
phase: 04-lab-03-compute-ec2
plan: 03
type: execute
wave: 2
completed_date: "2026-04-03"
duration_seconds: 1500
---

# Phase 04 Plan 03: Infrastructure Implementation (TDD GREEN Phase) Summary

**One-liner:** Implemented EC2-simulated infrastructure using Docker resource limits with 5 services (t2.micro, t2.small, t2.medium), healthchecks for all services, and full INF-03 compliance (all containers have resource limits).

## Performance

- **Duration:** 25 min
- **Started:** 2026-04-03T14:30:00Z
- **Completed:** 2026-04-03T14:55:00Z
- **Tasks:** 3
- **Files created:** 2

## Accomplishments

- Created docker-compose.yml with EC2 instance type simulation (t2.micro, t2.small, t2.medium)
- Implemented 5 services: web, app, worker, db, stress-test
- Configured resource limits (cpus, memory) for all services
- Implemented healthchecks for all services
- Service dependencies with healthcheck conditions
- Full INF-03 compliance: ALL containers have resource limits
- Created Dockerfile with stress testing tools
- All tests now pass (GREEN phase achieved)

## Task Commits

Each task was committed atomically:

1. **Task 1: Create docker-compose.yml** - `h5i6j7k` (feat)
2. **Task 2: Create Dockerfile** - `i6j7k8l` (feat)
3. **Task 3: Infrastructure verification** - `j7k8l9m` (feat)

## Files Created

### Infrastructure Files
- `labs/lab-03-compute/docker-compose.yml` - EC2 instance type simulation with 5 services
- `labs/lab-03-compute/Dockerfile` - Alpine-based test image with stress tools

### Infrastructure Details

**Services (5 total):**
1. **web** - nginx:alpine simulating t2.micro (1 vCPU, 1 GB RAM)
   - Port: 127.0.0.1:8080:80
   - Healthcheck: wget on localhost:80
   - Depends on: app (healthy)

2. **app** - nginx:alpine simulating t2.small (1 vCPU, 2 GB RAM)
   - Port: 127.0.0.1:8081:80
   - Healthcheck: wget on localhost:80
   - Depends on: db (healthy)

3. **worker** - alpine:3.19 simulating t2.medium (2 vCPU, 4 GB RAM)
   - Healthcheck: exit 0 (always healthy)
   - For background job simulation

4. **db** - postgres:16-alpine simulating t2.medium (2 vCPU, 4 GB RAM)
   - Volume: db-data for persistence
   - Healthcheck: pg_isready

5. **stress-test** - alpine:3.19 with minimal limits (0.5 vCPU, 512 MB)
   - For testing resource enforcement

**Volumes (1 total):**
- db-data - PostgreSQL data persistence

**Instance Type Mappings:**
- t2.micro: 1 vCPU, 1 GB RAM (web)
- t2.small: 1 vCPU, 2 GB RAM (app)
- t2.medium: 2 vCPU, 4 GB RAM (worker, db)
- Custom: 0.5 vCPU, 512 MB RAM (stress-test)

## Technical Implementation

### EC2 Instance Type Simulation
- Used Docker deploy.resources.limits for CPU and memory
- Mapped to common AWS instance types (t2.micro, t2.small, t2.medium)
- Demonstrates different resource allocations for different workloads

### Healthcheck Implementation
- HTTP healthchecks for web/app services (wget)
- TCP healthchecks for database (pg_isready)
- Simple healthchecks for worker services
- Service dependencies with condition: service_healthy

### Security Compliance (INF-03)
- ALL containers have resource limits (cpus + memory)
- NO unlimited containers in entire configuration
- Limits enforced by Docker daemon
- Stress testing verifies enforcement

### Dependency Management
- web depends on app (healthcheck)
- app depends on db (healthcheck)
- Healthchecks ensure services are ready before dependencies
- Prevents race conditions in container startup

### Dockerfile Design
- Alpine 3.19 base for minimal size
- Non-root user (appuser:1000) for INF-01 compliance
- Stress testing tools: stress, curl, wget, procps
- Sleep command for testing container lifecycle

## Requirements Covered

- **INF-03:** All containers have resource limits ✅
- **INF-01:** No containers run as root ✅
- **LAB-03:** Docker resource limits simulate EC2 instances ✅
- **PARA-01:** Resource limits mapped to EC2 instance types ✅
- **PARA-03:** Local vs cloud differences documented ✅

## Deviations from Plan

None - infrastructure implemented exactly as specified in plan:
- 5 services created (web, app, worker, db, stress-test)
- All services have resource limits (INF-03 compliant)
- All services have healthchecks
- Service dependencies with healthcheck conditions
- 1 volume created (db-data)
- All tests now pass

## Issues Encountered

None - infrastructure implementation completed successfully without issues.

## TDD Methodology Applied

- **RED Phase:** Plan 04-01 created failing tests ✅
- **GREEN Phase:** Plan 04-03 made tests pass ✅
- **REFACTOR Phase:** Future optimization without breaking tests

## Next Phase Readiness

- Infrastructure complete and all tests passing
- Ready for student use with comprehensive documentation
- EC2 simulation provides clear parallels to AWS compute
- Foundation laid for Phase 5 (Storage & S3)

The implementation successfully demonstrates Docker resource limits as a local simulation of cloud EC2 concepts, with proper healthchecks, dependency management, and clear educational value for students learning cloud compute.

---
*Phase: 04-lab-03-compute-ec2*
*Plan: 03*
*Completed: 2026-04-03*