add file lock test

Author: bobbyhouse

docs/database/testing/test_lock_release_simple.go

@@ -0,0 +1,173 @@
+package main
+
+import (
+	"fmt"
+	"os"
+	"os/signal"
+	"path/filepath"
+	"syscall"
+	"time"
+
+	"github.com/gofrs/flock"
+)
+
+// This is a simple program that demonstrates lock behavior.
+// Run it manually to see the behavior:
+//
+// Terminal 1: go run test_lock_release_simple.go acquire
+// Terminal 2: go run test_lock_release_simple.go check
+// Terminal 1: (kill with Ctrl+C or kill -9)
+// Terminal 2: go run test_lock_release_simple.go check    (now succeeds!)
+// Terminal 2: go run test_lock_release_simple.go cleanup
+
+func main() {
+	if len(os.Args) < 2 {
+		printUsage()
+		os.Exit(1)
+	}
+
+	lockFile := filepath.Join(os.TempDir(), "flock-test.lock")
+	fmt.Println(lockFile)
+
+	switch os.Args[1] {
+	case "acquire":
+		acquireLock(lockFile)
+	case "check":
+		checkLock(lockFile)
+	case "status":
+		showStatus(lockFile)
+	case "cleanup":
+		cleanup(lockFile)
+	default:
+		printUsage()
+		os.Exit(1)
+	}
+}
+
+func printUsage() {
+	fmt.Println("Usage:")
+	fmt.Println("  go run test_lock_release_simple.go acquire   - Acquire lock and hold it")
+	fmt.Println("  go run test_lock_release_simple.go check     - Try to acquire lock")
+	fmt.Println("  go run test_lock_release_simple.go status    - Check if lockfile exists")
+	fmt.Println("  go run test_lock_release_simple.go cleanup   - Remove lockfile")
+	fmt.Println()
+	fmt.Println("Test procedure:")
+	fmt.Println("  1. Terminal 1: run 'acquire' - holds lock indefinitely")
+	fmt.Println("  2. Terminal 2: run 'check' - should fail (lock held)")
+	fmt.Println("  3. Terminal 1: kill with Ctrl+C or kill -9")
+	fmt.Println("  4. Terminal 2: run 'check' again - should succeed!")
+	fmt.Println("  5. Terminal 2: run 'status' - lockfile still exists")
+	fmt.Println("  6. Terminal 2: run 'cleanup' - remove lockfile")
+}
+
+func acquireLock(lockFile string) {
+	fileLock := flock.New(lockFile)
+
+	fmt.Printf("[PID %d] Attempting to acquire lock on: %s\n", os.Getpid(), lockFile)
+
+	locked, err := fileLock.TryLock()
+	if err != nil {
+		fmt.Printf("❌ Error acquiring lock: %v\n", err)
+		os.Exit(1)
+	}
+
+	if !locked {
+		fmt.Printf("❌ Could not acquire lock (already held by another process)\n")
+		os.Exit(1)
+	}
+
+	fmt.Printf("✅ Lock acquired successfully!\n")
+	fmt.Printf("   Lockfile: %s\n", lockFile)
+	fmt.Printf("   PID: %d\n", os.Getpid())
+	fmt.Println()
+	fmt.Println("Holding lock indefinitely. Press Ctrl+C to exit gracefully,")
+	fmt.Println("or use 'kill -9' from another terminal to simulate a crash.")
+	fmt.Println()
+	fmt.Println("Commands to try in another terminal:")
+	fmt.Printf("  go run test_lock_release_simple.go check    # Try to acquire (should fail)\n")
+	fmt.Printf("  kill -9 %d                                  # Kill this process\n", os.Getpid())
+	fmt.Printf("  go run test_lock_release_simple.go check    # Try again (should succeed!)\n")
+	fmt.Println()
+
+	// Set up graceful shutdown
+	sigChan := make(chan os.Signal, 1)
+	signal.Notify(sigChan, os.Interrupt, syscall.SIGTERM)
+
+	go func() {
+		<-sigChan
+		fmt.Println("\n\nReceived interrupt signal, releasing lock...")
+		fileLock.Unlock()
+		fmt.Println("Lock released. Exiting.")
+		os.Exit(0)
+	}()
+
+	// Hold lock forever
+	for {
+		fmt.Printf(".")
+		time.Sleep(2 * time.Second)
+	}
+}
+
+func checkLock(lockFile string) {
+	fileLock := flock.New(lockFile)
+
+	fmt.Printf("[PID %d] Attempting to acquire lock on: %s\n", os.Getpid(), lockFile)
+
+	locked, err := fileLock.TryLock()
+	if err != nil {
+		fmt.Printf("❌ Error: %v\n", err)
+		os.Exit(1)
+	}
+
+	if !locked {
+		fmt.Printf("❌ Lock is currently held by another process\n")
+		fmt.Printf("   This means another process has the lock\n")
+		os.Exit(1)
+	}
+
+	fmt.Printf("✅ Successfully acquired lock!\n")
+	fmt.Printf("   This means no other process holds the lock\n")
+	fmt.Printf("   (The lock was either never acquired, or the holding process died)\n")
+
+	// Release it immediately
+	fileLock.Unlock()
+	fmt.Println("\nLock released.")
+}
+
+func showStatus(lockFile string) {
+	fmt.Printf("Lockfile path: %s\n", lockFile)
+
+	info, err := os.Stat(lockFile)
+	if os.IsNotExist(err) {
+		fmt.Println("Status: ❌ Lockfile does not exist")
+		return
+	}
+
+	if err != nil {
+		fmt.Printf("Error checking file: %v\n", err)
+		return
+	}
+
+	fmt.Printf("Status: ✅ Lockfile exists\n")
+	fmt.Printf("  Size: %d bytes\n", info.Size())
+	fmt.Printf("  Modified: %s\n", info.ModTime().Format(time.RFC3339))
+	fmt.Println("\nNote: The lockfile existing does NOT mean the lock is held.")
+	fmt.Println("      Run 'check' to see if the lock can be acquired.")
+}
+
+func cleanup(lockFile string) {
+	fmt.Printf("Removing lockfile: %s\n", lockFile)
+
+	err := os.Remove(lockFile)
+	if os.IsNotExist(err) {
+		fmt.Println("✅ Lockfile doesn't exist (already clean)")
+		return
+	}
+
+	if err != nil {
+		fmt.Printf("❌ Error removing file: %v\n", err)
+		os.Exit(1)
+	}
+
+	fmt.Println("✅ Lockfile removed successfully")
+}