feat: add lock-mgr CLI tool and wire into install script

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
2026-04-12 21:41:51 +01:00
parent 525436d64b
commit 311d9f4d9f
3 changed files with 326 additions and 1 deletions
--- a/lock-mgr/main.go
+++ b/lock-mgr/main.go
@@ -0,0 +1,314 @@
+package main
+
+import (
+	"crypto/rand"
+	"encoding/json"
+	"fmt"
+	"os"
+	"path/filepath"
+	"time"
+)
+
+type LockEntry struct {
+	Locked bool   `json:"locked"`
+	Key    string `json:"key,omitempty"`
+	Time   string `json:"time,omitempty"`
+}
+
+type LockFile map[string]*LockEntry
+
+func generateUUID() (string, error) {
+	b := make([]byte, 16)
+	if _, err := rand.Read(b); err != nil {
+		return "", err
+	}
+	b[6] = (b[6] & 0x0f) | 0x40 // version 4
+	b[8] = (b[8] & 0x3f) | 0x80 // variant bits
+	return fmt.Sprintf("%x-%x-%x-%x-%x", b[0:4], b[4:6], b[6:8], b[8:10], b[10:16]), nil
+}
+
+func readLockFile(path string) (LockFile, error) {
+	data, err := os.ReadFile(path)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return make(LockFile), nil
+		}
+		return nil, fmt.Errorf("read lock file: %w", err)
+	}
+	if len(data) == 0 {
+		return make(LockFile), nil
+	}
+	var lf LockFile
+	if err := json.Unmarshal(data, &lf); err != nil {
+		return make(LockFile), nil
+	}
+	if lf == nil {
+		return make(LockFile), nil
+	}
+	return lf, nil
+}
+
+func writeLockFile(path string, lf LockFile) error {
+	data, err := json.MarshalIndent(lf, "", "  ")
+	if err != nil {
+		return fmt.Errorf("marshal lock file: %w", err)
+	}
+	return os.WriteFile(path, data, 0644)
+}
+
+// acquireMgrLock implements steps 3-8: acquire the meta-lock on the JSON file itself.
+// Returns the mgr-key on success.
+func acquireMgrLock(mgrPath string) (string, error) {
+	// Step 3: generate mgr-key once
+	mgrKey, err := generateUUID()
+	if err != nil {
+		return "", err
+	}
+
+	for {
+		// Step 4: record current time
+		startTime := time.Now()
+
+		// Steps 5-6: spin until the meta-lock is free or owned by us
+		for {
+			lf, err := readLockFile(mgrPath)
+			if err != nil {
+				return "", err
+			}
+			entry := lf[mgrPath]
+			if entry == nil || !entry.Locked || entry.Key == mgrKey {
+				break
+			}
+			if time.Since(startTime) > 5*time.Second {
+				return "", fmt.Errorf("timeout waiting to acquire manager lock")
+			}
+			time.Sleep(100 * time.Millisecond)
+		}
+
+		// Step 7: write locked=true, key=mgrKey
+		lf, err := readLockFile(mgrPath)
+		if err != nil {
+			return "", err
+		}
+		if lf[mgrPath] == nil {
+			lf[mgrPath] = &LockEntry{}
+		}
+		lf[mgrPath].Locked = true
+		lf[mgrPath].Key = mgrKey
+		if err := writeLockFile(mgrPath, lf); err != nil {
+			return "", err
+		}
+
+		// Step 8: verify we actually won the race
+		lf2, err := readLockFile(mgrPath)
+		if err != nil {
+			return "", err
+		}
+		if lf2[mgrPath] != nil && lf2[mgrPath].Key == mgrKey {
+			return mgrKey, nil
+		}
+		// Lost the race; go back to step 4 (keep same mgrKey, reset timer)
+	}
+}
+
+// releaseMgrLock removes the meta-lock entry and writes the file.
+func releaseMgrLock(mgrPath string) error {
+	lf, err := readLockFile(mgrPath)
+	if err != nil {
+		return err
+	}
+	delete(lf, mgrPath)
+	return writeLockFile(mgrPath, lf)
+}
+
+func cmdAcquire(mgrPath, filePath string) error {
+	// Steps 3-8: acquire meta-lock
+	if _, err := acquireMgrLock(mgrPath); err != nil {
+		return err
+	}
+
+	// Step 9: record start time for file-lock wait timeout
+	startTime := time.Now()
+
+	for {
+		// Step 10: read current file lock state
+		lf, err := readLockFile(mgrPath)
+		if err != nil {
+			_ = releaseMgrLock(mgrPath)
+			return err
+		}
+
+		entry := lf[filePath]
+		xLocked := entry != nil && entry.Locked
+		xKey := ""
+		if entry != nil {
+			xKey = entry.Key
+		}
+
+		envKey := os.Getenv("LOCK_MGR_KEY")
+
+		// Step 11: if locked by someone else, wait and retry
+		if xLocked && xKey != envKey {
+			if time.Since(startTime) > 30*time.Second {
+				_ = releaseMgrLock(mgrPath)
+				return fmt.Errorf("timeout waiting to acquire lock on %s", filePath)
+			}
+			// Release meta-lock while sleeping so others can proceed
+			if err := releaseMgrLock(mgrPath); err != nil {
+				return err
+			}
+			time.Sleep(1 * time.Second)
+			// Re-acquire meta-lock before next read
+			if _, err := acquireMgrLock(mgrPath); err != nil {
+				return err
+			}
+			continue
+		}
+
+		// Step 12: not locked (or already owned by us) — acquire
+		var newKey string
+		if envKey != "" {
+			newKey = envKey
+		} else {
+			newKey, err = generateUUID()
+			if err != nil {
+				_ = releaseMgrLock(mgrPath)
+				return err
+			}
+		}
+
+		if lf[filePath] == nil {
+			lf[filePath] = &LockEntry{}
+		}
+		lf[filePath].Locked = true
+		lf[filePath].Key = newKey
+		lf[filePath].Time = time.Now().UTC().Format(time.RFC3339)
+
+		// Step 13: delete meta-lock entry and write atomically
+		delete(lf, mgrPath)
+		if err := writeLockFile(mgrPath, lf); err != nil {
+			return err
+		}
+
+		fmt.Println(newKey)
+		return nil
+	}
+}
+
+func cmdRelease(mgrPath, filePath string) error {
+	// Steps 3-8: acquire meta-lock
+	if _, err := acquireMgrLock(mgrPath); err != nil {
+		return err
+	}
+
+	lf, err := readLockFile(mgrPath)
+	if err != nil {
+		_ = releaseMgrLock(mgrPath)
+		return err
+	}
+
+	entry := lf[filePath]
+	xLocked := entry != nil && entry.Locked
+	xKey := ""
+	if entry != nil {
+		xKey = entry.Key
+	}
+
+	envKey := os.Getenv("LOCK_MGR_KEY")
+
+	// Step 14: validate preconditions
+	if envKey == "" {
+		_ = releaseMgrLock(mgrPath)
+		return fmt.Errorf("LOCK_MGR_KEY environment variable not set")
+	}
+	if !xLocked {
+		_ = releaseMgrLock(mgrPath)
+		return fmt.Errorf("file %s is not locked", filePath)
+	}
+	if xKey != envKey {
+		_ = releaseMgrLock(mgrPath)
+		return fmt.Errorf("LOCK_MGR_KEY does not match the lock key for %s", filePath)
+	}
+
+	// Step 15: delete file lock and meta-lock, write
+	delete(lf, filePath)
+	delete(lf, mgrPath)
+	return writeLockFile(mgrPath, lf)
+}
+
+func cmdForceUnlock(mgrPath, filePath string) error {
+	// Steps 3-8: acquire meta-lock
+	if _, err := acquireMgrLock(mgrPath); err != nil {
+		return err
+	}
+
+	lf, err := readLockFile(mgrPath)
+	if err != nil {
+		_ = releaseMgrLock(mgrPath)
+		return err
+	}
+
+	// Remove file lock and meta-lock unconditionally
+	delete(lf, filePath)
+	delete(lf, mgrPath)
+	return writeLockFile(mgrPath, lf)
+}
+
+func main() {
+	if len(os.Args) < 3 {
+		fmt.Fprintln(os.Stderr, "Usage: lock-mgr <acquire|release|force-unlock> <file>")
+		os.Exit(1)
+	}
+
+	action := os.Args[1]
+	fileArg := os.Args[2]
+
+	// Step 1: resolve tool directory and locate (or create) the lock file
+	execPath, err := os.Executable()
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "error: cannot determine executable path: %v\n", err)
+		os.Exit(1)
+	}
+
+	toolDir := filepath.Dir(execPath)
+	rawMgrPath := filepath.Join(toolDir, "..", ".lock-mgr.json")
+
+	// Step 2: get absolute paths
+	mgrPath, err := filepath.Abs(rawMgrPath)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "error: cannot resolve lock file path: %v\n", err)
+		os.Exit(1)
+	}
+
+	filePath, err := filepath.Abs(fileArg)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "error: cannot resolve file path: %v\n", err)
+		os.Exit(1)
+	}
+
+	// Ensure lock file exists
+	if _, statErr := os.Stat(mgrPath); os.IsNotExist(statErr) {
+		if writeErr := os.WriteFile(mgrPath, []byte("{}"), 0644); writeErr != nil {
+			fmt.Fprintf(os.Stderr, "error: cannot create lock file: %v\n", writeErr)
+			os.Exit(1)
+		}
+	}
+
+	switch action {
+	case "acquire":
+		err = cmdAcquire(mgrPath, filePath)
+	case "release":
+		err = cmdRelease(mgrPath, filePath)
+	case "force-unlock":
+		err = cmdForceUnlock(mgrPath, filePath)
+	default:
+		fmt.Fprintf(os.Stderr, "error: unknown action %q\n", action)
+		fmt.Fprintln(os.Stderr, "Usage: lock-mgr <acquire|release|force-unlock> <file>")
+		os.Exit(1)
+	}
+
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "error: %v\n", err)
+		os.Exit(1)
+	}
+}