resident_lease.go RawHistoryFolder

1package subagents
2
3import (
4	"errors"
5	"fmt"
6	"os"
7	"path/filepath"
8)
9
10const residentLeaseName = "owner.lock"
11
12// ErrResidentLeaseBusy means another zut process owns this resident journal.
13// Callers must not read the authoritative transcript or mutate its projections.
14var ErrResidentLeaseBusy = errors.New("resident journal: owned by another process")
15
16// residentLease keeps the OS-owned exclusive lock alive for a resident's full
17// writer lifetime. The lock file is deliberately stable: deleting or replacing
18// it would permit separate processes to lock different filesystem objects.
19type residentLease struct {
20	file *os.File
21}
22
23func acquireResidentLease(dir string) (*residentLease, error) {
24	file, err := os.OpenFile(filepath.Join(dir, residentLeaseName), os.O_CREATE|os.O_RDWR, 0o600)
25	if err != nil {
26		return nil, fmt.Errorf("resident journal lease: %w", err)
27	}
28	_ = file.Chmod(0o600)
29	if err := lockResidentLease(file); err != nil {
30		_ = file.Close()
31		if errors.Is(err, ErrResidentLeaseBusy) {
32			return nil, err
33		}
34		return nil, fmt.Errorf("resident journal lease lock: %w", err)
35	}
36	return &residentLease{file: file}, nil
37}
38
39func (l *residentLease) Close() error {
40	if l == nil || l.file == nil {
41		return nil
42	}
43	file := l.file
44	l.file = nil
45	unlockErr := unlockResidentLease(file)
46	closeErr := file.Close()
47	return errors.Join(unlockErr, closeErr)
48}