CoreControl/agent/main.go

package main

import (
	"context"
	"database/sql"
	"fmt"
	"net/http"
	"os"
	"time"

	_ "github.com/jackc/pgx/v4/stdlib" // Wird für die Registrierung des pgx Treibers benötigt
	"github.com/joho/godotenv"
)

type Application struct {
	ID        int
	PublicURL string
	Online    bool
}

func main() {
	if err := godotenv.Load(); err != nil {
		fmt.Println("No env vars found")
	}

	dbURL := os.Getenv("DATABASE_URL")
	if dbURL == "" {
		panic("DATABASE_URL not set")
	}

	db, err := sql.Open("pgx", dbURL)
	if err != nil {
		panic(fmt.Sprintf("Database connection failed: %v\n", err))
	}
	defer db.Close()

	ticker := time.NewTicker(5 * time.Second)
	defer ticker.Stop()

	client := &http.Client{
		Timeout: 4 * time.Second,
	}

	for range ticker.C {
		apps := getApplications(db)
		checkAndUpdateStatus(db, client, apps)
	}
}

func getApplications(db *sql.DB) []Application {
	rows, err := db.Query(`
        SELECT id, "publicURL", online 
        FROM application 
        WHERE "publicURL" IS NOT NULL
    `)
	if err != nil {
		fmt.Printf("Error fetching applications: %v\n", err)
		return nil
	}
	defer rows.Close()

	var apps []Application
	for rows.Next() {
		var app Application
		err := rows.Scan(&app.ID, &app.PublicURL, &app.Online)
		if err != nil {
			fmt.Printf("Error scanning row: %v\n", err)
			continue
		}
		apps = append(apps, app)
	}
	return apps
}

func checkAndUpdateStatus(db *sql.DB, client *http.Client, apps []Application) {
	for _, app := range apps {
		ctx, cancel := context.WithTimeout(context.Background(), 4*time.Second)
		defer cancel()

		req, err := http.NewRequestWithContext(ctx, "HEAD", app.PublicURL, nil)
		if err != nil {
			fmt.Printf("Error creating request: %v\n", err)
			continue
		}

		resp, err := client.Do(req)
		isOnline := false
		if err == nil && resp.StatusCode >= 200 && resp.StatusCode < 300 {
			isOnline = true
		}

		_, err = db.ExecContext(ctx,
			"UPDATE application SET online = $1 WHERE id = $2",
			isOnline,
			app.ID,
		)
		if err != nil {
			fmt.Printf("Update failed for app %d: %v\n", app.ID, err)
		}
	}
}