Lab01

app_go/.gitignore

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+# Go binaries / build output
+devops-info-service
+*.exe
+*.out
+*.test
+bin/
+dist/
+
+# IDE/editor
+.vscode/
+.idea/
+
+# OS files
+.DS_Store
+Thumbs.db
+
+# Logs
+*.log

app_go/README.md

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+# devops-info-service (Go)
+
+## Overview
+`devops-info-service` is a lightweight HTTP service written in Go. It returns:
+- service metadata (name, version, description, framework),
+- system information (hostname, OS/platform, architecture, CPU count, Go version),
+- runtime information (uptime, current UTC time),
+- request information (client IP, user-agent, method, path),
+- a list of available endpoints.
+
+This is useful for DevOps labs and basic observability: quick environment inspection and health checks.
+
+---
+
+## Prerequisites
+- **Go:** 1.22+ (recommended)
+- No external dependencies (standard library only)
+
+---
+
+## Installation
+```bash
+cd app_go
+go mod tidy
+```
+
+## Running the Application
+```bash
+go run .
+```
+
+## API Endpoints
+- `GET /` - Service and system information
+- `GET /health` - Health check
+
+## Configuration
+
+The application is configured using environment variables.
+
+| Variable | Default | Description | Example |
+|---------|---------|-------------|---------|
+| `HOST`  | `0.0.0.0` | Host interface to bind the server to | `0.0.0.0` |
+| `PORT`  | `8080` | Port the server listens on | `8080` |

app_go/docs/GO.md

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+### Why Go?
+- **Compiled binary**: produces a single executable (useful for multi-stage Docker builds).
+- **Fast startup and low overhead**: good for microservices.
+- **Standard library is enough**: `net/http` covers routing and HTTP server without external frameworks.
+- **Great DevOps fit**: simple deployment, small runtime requirements.

app_go/docs/LAB01.md

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+# Lab 1 (Bonus) — DevOps Info Service in Go
+
+## 1. Language / Framework Selection
+
+### Choice
+I implemented the bonus service in **Go** using the standard library **net/http** package.
+
+### Why Go?
+- **Compiled binary**: produces a single executable (useful for multi-stage Docker builds).
+- **Fast startup and low overhead**: good for microservices.
+- **Standard library is enough**: `net/http` covers routing and HTTP server without external frameworks.
+- **Great DevOps fit**: simple deployment, small runtime requirements.
+
+### Comparison with Alternatives
+
+| Criteria | Go (net/http) (chosen) | Rust | Java (Spring Boot) | C# (ASP.NET Core) |
+|---------|--------------------------|------|---------------------|-------------------|
+| Build artifact | Single binary | Single binary | JVM app + deps | .NET app + deps |
+| Startup time | Fast | Fast | Usually slower | Medium |
+| Runtime deps | None | None | JVM required | .NET runtime |
+| HTTP stack | stdlib | frameworks (Axum/Actix) | Spring ecosystem | ASP.NET stack |
+| Complexity | Low | Medium–high | Medium | Medium |
+| Best fit for this lab | Excellent | Good | Overkill | Good |
+
+---
+
+## 2. Best Practices Applied
+
+### 2.1 Clean Code Organization
+- Clear data models (`ServiceInfo`, `Service`, `System`, `RuntimeInfo`, `RequestInfo`, `Endpoint`).
+- Helper functions for concerns separation:
+  - `runtimeInfo()`, `requestInfo()`, `uptime()`, `isoUTCNow()`, `clientIP()`, `writeJSON()`.
+
+### 2.2 Configuration via Environment Variables
+The service is configurable via environment variables:
+- `HOST` (default `0.0.0.0`)
+- `PORT` (default `8080`)
+- `DEBUG` (default `false`)
+
+Implementation uses a simple helper:
+```go
+func getenv(key, def string) string {
+    v := os.Getenv(key)
+    if v == "" {
+        return def
+    }
+    return v
+}
+```
+
+### 2.3 Logging Middleware
+Request logging is implemented as middleware:
+```go
+func withLogging(logger *log.Logger) func(http.Handler) http.Handler {
+    return func(next http.Handler) http.Handler {
+        return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+            start := time.Now()
+            next.ServeHTTP(w, r)
+            logger.Printf("%s %s (%s) from %s in %s",
+                r.Method, r.URL.Path, r.Proto, r.RemoteAddr, time.Since(start))
+        })
+    }
+}
+```
+
+### 2.4 Error Handling
+#### 404 Not Found
+Unknown endpoints return a consistent JSON error:
+```json
+{
+  "error": "Not Found",
+  "message": "Endpoint does not exist"
+}
+```
+This is implemented via a wrapper that enforces valid paths:
+```go
+func withNotFound(next http.Handler) http.Handler {
+    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+        if r.URL.Path != "/" && r.URL.Path != "/health" {
+            writeJSON(w, http.StatusNotFound, ErrorResponse{
+                Error: "Not Found",
+                Message: "Endpoint does not exist",
+            })
+            return
+        }
+        next.ServeHTTP(w, r)
+    })
+}
+```
+#### 500 Internal Server Error (panic recovery)
+A recover middleware prevents crashes and returns a safe JSON response:
+```go
+func withRecover(logger *log.Logger) func(http.Handler) http.Handler {
+    return func(next http.Handler) http.Handler {
+        return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+            defer func() {
+                if rec := recover(); rec != nil {
+                    logger.Printf("panic recovered: %v", rec)
+                    writeJSON(w, http.StatusInternalServerError, ErrorResponse{
+                        Error: "Internal Server Error",
+                        Message: "An unexpected error occurred",
+                    })
+                }
+            }()
+            next.ServeHTTP(w, r)
+        })
+    }
+}
+```
+### 2.5 Production-Friendly HTTP Server Settings
+The service uses `http.Server` with timeouts:
+```go
+srv := &http.Server{
+    Addr: addr,
+    Handler: handler,
+    ReadHeaderTimeout: 5 * time.Second,
+}
+```
+## 3. API Documentation
+### 3.1 GET / — Service and System Information
+**Description**: Returns service metadata, system info, runtime info, request info, and available endpoints.
+
+**Request**:
+```bash
+curl -i http://127.0.0.1:8080/
+```
+**Response (200 OK) example**:
+```json
+{
+  "service": {
+    "name": "devops-info-service",
+    "version": "1.0.0",
+    "description": "DevOps course info service",
+    "framework": "Go net/http"
+  },
+  "system": {
+    "hostname": "DESKTOP-KUN1CI4",
+    "platform": "windows",
+    "platform_version": "unknown",
+    "architecture": "amd64",
+    "cpu_count": 8,
+    "go_version": "go1.25.6"
+  },
+  "runtime": {
+    "uptime_seconds": 6,
+    "uptime_human": "0 hours, 0 minutes",
+    "current_time": "2026-01-25T17:17:32.248Z",
+    "timezone": "UTC"
+  },
+  "request": {
+    "client_ip": "::1",
+    "user_agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/144.0.0.0 Safari/537.36 Edg/144.0.0.0",
+    "method": "GET",
+    "path": "/"
+  },
+  "endpoints": [
+    {
+      "path": "/",
+      "method": "GET",
+      "description": "Service information"
+    },
+    {
+      "path": "/health",
+      "method": "GET",
+      "description": "Health check"
+    }
+  ]
+}
+```
+### 3.2 GET /health — Health Check
+**Description**: Description: Simple health endpoint used for monitoring and probes.
+
+**Request**:
+```bash
+curl -i http://127.0.0.1:8080/health
+```
+**Response (200 OK) example**:
+```json
+{
+  "status": "healthy",
+  "timestamp": "2026-01-25T17:19:02.582Z",
+  "uptime_seconds": 96
+}
+```
+### 3.3 404 Behavior
+**Request**:
+```bash
+curl -i http://127.0.0.1:8080/does-not-exist
+```
+**Response (404 Not Found)**:
+```json
+{
+  "error": "Not Found",
+  "message": "Endpoint does not exist"
+}
+```
+
+## 4. Build & Run Instructions
+### 4.1 Run locally (no build)
+```bash
+go run main.go
+```
+### 4.2 Build binary
+```bash
+go build -o devops-info-service main.go
+```
+Run:
+```bash
+./devops-info-service
+```
+### 4.3 Environment variables examples
+```bash
+HOST=127.0.0.1 PORT=3000 ./devops-info-service
+DEBUG=true PORT=8081 ./devops-info-service
+```
+## 5. Challenges & Solutions
+I don't know how `go` works.

app_go/go.mod

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+module devops-info-service
+
+go 1.22