Lab02

app_go/.dockerignore

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+# Go build cache
+*.exe
+*.exe~
+*.dll
+*.so
+*.dylib
+*.test
+*.out
+go.work
+
+# Compiled binary
+devops-info-service
+
+# Go workspace
+vendor/
+
+# Git
+.git/
+.gitignore
+.gitattributes
+
+# IDE
+.vscode/
+.idea/
+*.swp
+*.swo
+*~
+
+# Documentation (not needed in container)
+README.md
+docs/
+*.md
+
+# Screenshots
+*.png
+*.jpg
+*.jpeg
+
+# OS
+.DS_Store
+Thumbs.db
+
+# Lab files
+labs/

app_go/Dockerfile

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+###############################################################################
+# Stage 1: Builder
+# Purpose: Compile the Go application
+# Base image: Full Go SDK with build tools
+###############################################################################
+FROM golang:1.21-alpine AS builder
+
+# Set the working directory inside the container
+WORKDIR /build
+
+# Install git and other build dependencies (if needed for go mod download)
+RUN apk add --no-cache git ca-certificates
+
+# Copy go mod files first for better layer caching
+# This layer will only be rebuilt when dependencies change
+COPY go.mod go.sum* ./
+
+# Download dependencies
+RUN go mod download
+
+# Copy source code
+COPY main.go .
+
+# Build the application
+# -ldflags="-s -w" strips debug information to reduce binary size
+# -o specifies the output filename
+RUN CGO_ENABLED=0 GOOS=linux go build -ldflags="-s -w" -o devops-info-service .
+
+
+###############################################################################
+# Stage 2: Runtime
+# Purpose: Run the application with minimal footprint
+# Base image: Alpine Linux (minimal but with basic tools)
+###############################################################################
+FROM alpine:3.19
+
+# Install ca-certificates for HTTPS and wget for healthcheck
+RUN apk add --no-cache ca-certificates wget
+
+# Create non-root user
+RUN addgroup -g 1000 appuser && \
+    adduser -D -u 1000 -G appuser appuser
+
+# Copy CA certificates from builder
+COPY --from=builder /etc/ssl/certs/ca-certificates.crt /etc/ssl/certs/
+
+# Copy the compiled binary from builder stage
+COPY --from=builder /build/devops-info-service /usr/local/bin/devops-info-service
+
+# Set ownership to non-root user
+RUN chown appuser:appuser /usr/local/bin/devops-info-service
+
+# Switch to non-root user
+USER appuser
+
+# Expose the application port
+EXPOSE 8080
+
+# Set default environment variables
+ENV HOST=0.0.0.0 \
+    PORT=8080
+
+# Health check
+HEALTHCHECK --interval=30s --timeout=3s --start-period=5s --retries=3 \
+    CMD wget --no-verbose --tries=1 --spider http://localhost:8080/health || exit 1
+
+# Run the binary
+ENTRYPOINT ["/usr/local/bin/devops-info-service"]

app_go/README.md

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+# DevOps Info Service (Go)
+
+A production-ready Go web service that provides comprehensive information about itself and its runtime environment. This is the compiled language version of the Python service, demonstrating multi-stage Docker build capabilities.
+
+## Overview
+
+The Go implementation of the DevOps Info Service is a lightweight, high-performance REST API that returns detailed system information, health status, and service metadata. This version demonstrates the advantages of compiled languages for containerized applications.
+
+## Prerequisites
+
+- Go 1.21 or higher
+
+## Building
+
+### Build for current platform
+```bash
+go build -o devops-info-service main.go
+```
+
+### Build for specific platforms
+```bash
+# Linux
+GOOS=linux GOARCH=amd64 go build -o devops-info-service-linux main.go
+
+# macOS (Apple Silicon)
+GOOS=darwin GOARCH=arm64 go build -o devops-info-service-darwin-arm64 main.go
+
+# macOS (Intel)
+GOOS=darwin GOARCH=amd64 go build -o devops-info-service-darwin-amd64 main.go
+
+# Windows
+GOOS=windows GOARCH=amd64 go build -o devops-info-service.exe main.go
+```
+
+## Running the Application
+
+### Using go run
+```bash
+go run main.go
+```
+
+### Using compiled binary
+```bash
+./devops-info-service
+```
+
+### With custom configuration
+```bash
+# Custom port
+PORT=9090 go run main.go
+
+# Custom host and port
+HOST=127.0.0.1 PORT=3000 go run main.go
+```
+
+## API Endpoints
+
+### GET /
+
+Returns comprehensive service and system information.
+
+**Response:**
+```json
+{
+  "service": {
+    "name": "devops-info-service",
+    "version": "1.0.0",
+    "description": "DevOps course info service",
+    "framework": "Go net/http"
+  },
+  "system": {
+    "hostname": "Mac",
+    "platform": "darwin",
+    "platform_version": "unknown",
+    "architecture": "arm64",
+    "cpu_count": 10,
+    "go_version": "go1.24.0"
+  },
+  "runtime": {
+    "uptime_seconds": 27,
+    "uptime_human": "27 seconds",
+    "current_time": "2026-01-27T19:29:02Z",
+    "timezone": "UTC"
+  },
+  "request": {
+    "client_ip": "127.0.0.1",
+    "user_agent": "curl/8.7.1",
+    "method": "GET",
+    "path": "/"
+  },
+  "endpoints": [
+    {
+      "path": "/",
+      "method": "GET",
+      "description": "Service information"
+    },
+    {
+      "path": "/health",
+      "method": "GET",
+      "description": "Health check"
+    }
+  ]
+}
+```
+
+### GET /health
+
+Simple health check endpoint for monitoring and Kubernetes probes.
+
+**Response:**
+```json
+{
+  "status": "healthy",
+  "timestamp": "2026-01-27T20:04:18Z",
+  "uptime_seconds": 84
+}
+```
+
+## Configuration
+
+The application can be configured via environment variables:
+
+| Variable | Default | Description |
+|----------|---------|-------------|
+| `HOST` | `0.0.0.0` | Host to bind the server to |
+| `PORT` | `8080` | Port number for the server |
+
+## Binary Size Comparison
+
+| Language | Binary Size | Startup Time | Memory Usage |
+|----------|-------------|--------------|--------------|
+| **Go** | ~2-3 MB | Instant | ~2-3 MB |
+| Python | N/A (interpreter) | ~100ms | ~20-30 MB |
+
+## Advantages of Go Implementation
+
+1. **Small Binary Size**: The compiled binary is only 2-3 MB, compared to Python's interpreter + dependencies
+2. **Fast Startup**: Instant startup time vs Python's interpreter overhead
+3. **Low Memory Usage**: Significantly lower memory footprint
+4. **Single Binary**: No dependencies to manage, just copy the binary
+5. **Cross-Compilation**: Easily build for any platform from any machine
+6. **Performance**: Better performance and concurrency support
+
+## Project Structure
+
+```
+app_go/
+├── main.go                  # Main application
+├── go.mod                   # Go module definition
+├── README.md                # This file
+└── docs/                    # Lab documentation
+    ├── LAB01.md            # Implementation details
+    ├── GO.md               # Language justification
+    └── screenshots/        # Proof of work
+```
+
+## Examples
+
+### Testing with curl
+```bash
+# Main endpoint
+curl http://localhost:8080/
+
+# Health check
+curl http://localhost:8080/health
+
+# Pretty print JSON
+curl http://localhost:8080/ | jq
+```
+
+### Build and run
+```bash
+# Build
+go build -o devops-info-service main.go
+
+# Run
+./devops-info-service
+
+# Test
+curl http://localhost:8080/
+```
+
+## Future Enhancements
+
+This Go implementation will be used in Lab 2 to demonstrate:
+- Multi-stage Docker builds
+- Smaller final image size
+- Static binary compilation
+- Alpine-based containers
+
+## License
+
+Educational use for DevOps course.