Commit `c097185877`

c0971858774b369ce0c3928bcd593ce36aff92e9

parent: 846c4cbe36

Verified · cmc

cmc <hello@cleberg.net> · 2026-09-26 18:49 UTC

Close watcher gaps

- Event overflow reschedules a rescan instead of only logging.
- Start watching before the first scan; serialise rescans with a mutex.
- Refuse to start when the cache directory is inside the photo root.

Closes #3

Layout: unified · split

cmd/gallery/main.go +29 −4

		@@ -11,6 +11,8 @@ import (
11	11	"os/signal"
12	12	"path/filepath"
13	13	"runtime"
	14	"strings"
	15	"sync"
14	16	"syscall"
15	17	"time"
16	18
		@@ -27,6 +29,23 @@ func env(key, def string) string {
27	29	return def
28	30	}
29	31
	32	// checkDirs rejects a cache inside the photo root: every scan rewrites
	33	// meta.json, which the watcher would report as a change, forever.
	34	func checkDirs(photos, cache string) error {
	35	p, err := filepath.Abs(photos)
	36	if err != nil {
	37	return err
	38	}
	39	c, err := filepath.Abs(cache)
	40	if err != nil {
	41	return err
	42	}
	43	if rel, err := filepath.Rel(p, c); err == nil && (rel == "." \|\| !strings.HasPrefix(rel, "..")) {
	44	return fmt.Errorf("cache %s must not be inside photos %s", cache, photos)
	45	}
	46	return nil
	47	}
	48
30	49	func main() {
31	50	photos := flag.String("photos", env("GALLERY_PHOTOS", ""), "photo root (required)")
32	51	cache := flag.String("cache", env("GALLERY_CACHE", ""), "cache directory (required)")
		@@ -40,6 +59,9 @@ func main() {
40	59	flag.Usage()
41	60	os.Exit(2)
42	61	}
	62	if err := checkDirs(photos, cache); err != nil {
	63	log.Fatal(err)
	64	}
43	65	if err := format.CheckTools(); err != nil {
44	66	log.Fatal(err)
45	67	}
		@@ -51,7 +73,10 @@ func main() {
51	73	}
52	74	rend := render.New(*cache, runtime.NumCPU())
53	75	store := &library.Store{}
	76	var scanMu sync.Mutex
54	77	rescan := func() error {
	78	scanMu.Lock()
	79	defer scanMu.Unlock()
55	80	lib, err := library.Scan(*photos, reg, meta)
56	81	if err != nil {
57	82	return err
		@@ -65,10 +90,6 @@ func main() {
65	90	log.Printf("library: %d albums", len(lib.Albums))
66	91	return nil
67	92	}
68		if err := rescan(); err != nil {
69		log.Fatal(err)
70		}
71
72	93	ctx, stop := signal.NotifyContext(context.Background(), os.Interrupt, syscall.SIGTERM)
73	94	defer stop()
74	95	onChange := func() {
		@@ -76,9 +97,13 @@ func main() {
76	97	log.Printf("rescan: %v", err)
77	98	}
78	99	}
	100	// Watch before the first scan so files added during it are not missed.
79	101	if err := library.Watch(ctx, photos, 500time.Millisecond, onChange); err != nil {
80	102	log.Fatal(err)
81	103	}
	104	if err := rescan(); err != nil {
	105	log.Fatal(err)
	106	}
82	107
83	108	opt := web.Options{Title: title, ThemePath: theme}
84	109	if *templates != "" {

cmd/gallery/main_test.go added +27

		@@ -0,0 +1,27 @@
	1	package main
	2
	3	import (
	4	"path/filepath"
	5	"testing"
	6	)
	7
	8	func TestCheckDirs(t *testing.T) {
	9	root := t.TempDir()
	10	photos := filepath.Join(root, "photos")
	11	for _, tc := range []struct {
	12	cache string
	13	ok bool
	14	}{
	15	{filepath.Join(root, "cache"), true},
	16	{filepath.Join(root, "photos-cache"), true},
	17	{photos, false},
	18	{filepath.Join(photos, "cache"), false},
	19	{filepath.Join(photos, ".cache"), false},
	20	{filepath.Join(photos, "a", "..", "cache"), false},
	21	} {
	22	err := checkDirs(photos, tc.cache)
	23	if (err == nil) != tc.ok {
	24	t.Errorf("checkDirs(%q, %q) = %v, want ok=%v", photos, tc.cache, err, tc.ok)
	25	}
	26	}
	27	}

internal/library/watch.go +33 −23

		@@ -2,6 +2,7 @@ package library
2	2
3	3	import (
4	4	"context"
	5	"errors"
5	6	"log"
6	7	"os"
7	8	"path/filepath"
		@@ -23,35 +24,44 @@ func Watch(ctx context.Context, root string, debounce time.Duration, onChange fu
23	24	}
24	25	go func() {
25	26	defer w.Close()
26		timer := time.NewTimer(debounce)
27		timer.Stop()
28		for {
29		select {
30		case <-ctx.Done():
	27	watchLoop(ctx, w.Events, w.Errors, w.Add, debounce, onChange)
	28	}()
	29	return nil
	30	}
	31
	32	// watchLoop debounces events into onChange calls and watches newly created directories.
	33	// An event overflow means changes were dropped, so it schedules a rescan too.
	34	func watchLoop(ctx context.Context, events <-chan fsnotify.Event, errs <-chan error, add func(string) error, debounce time.Duration, onChange func()) {
	35	timer := time.NewTimer(debounce)
	36	timer.Stop()
	37	for {
	38	select {
	39	case <-ctx.Done():
	40	return
	41	case ev, ok := <-events:
	42	if !ok {
31	43	return
32		case ev, ok := <-w.Events:
33		if !ok {
34		return
35		}
36		if ev.Has(fsnotify.Create) {
37		if fi, err := os.Stat(ev.Name); err == nil && fi.IsDir() {
38		if err := w.Add(ev.Name); err != nil {
39		log.Printf("watch %s: %v", ev.Name, err)
40		}
	44	}
	45	if ev.Has(fsnotify.Create) {
	46	if fi, err := os.Stat(ev.Name); err == nil && fi.IsDir() {
	47	if err := add(ev.Name); err != nil {
	48	log.Printf("watch %s: %v", ev.Name, err)
41	49	}
42	50	}
	51	}
	52	timer.Reset(debounce)
	53	case err, ok := <-errs:
	54	if !ok {
	55	return
	56	}
	57	log.Printf("watch: %v", err)
	58	if errors.Is(err, fsnotify.ErrEventOverflow) {
43	59	timer.Reset(debounce)
44		case err, ok := <-w.Errors:
45		if !ok {
46		return
47		}
48		log.Printf("watch: %v", err)
49		case <-timer.C:
50		onChange()
51	60	}
	61	case <-timer.C:
	62	onChange()
52	63	}
53		}()
54		return nil
	64	}
55	65	}
56	66
57	67	func addTree(w *fsnotify.Watcher, root string) error {

internal/library/watch_test.go +14

		@@ -6,6 +6,8 @@ import (
6	6	"path/filepath"
7	7	"testing"
8	8	"time"
	9
	10	"github.com/fsnotify/fsnotify"
9	11	)
10	12
11	13	func expectCall(t *testing.T, ch <-chan struct{}, what string) {
		@@ -43,3 +45,15 @@ func TestWatchDebouncesAndFollowsNewDirs(t *testing.T) {
43	45	os.WriteFile(filepath.Join(root, "iceland", "a.jpg"), []byte("x"), 0o644)
44	46	expectCall(t, calls, "write in new album")
45	47	}
	48
	49	func TestWatchLoopOverflowTriggersRescan(t *testing.T) {
	50	ctx, cancel := context.WithCancel(context.Background())
	51	defer cancel()
	52	events := make(chan fsnotify.Event)
	53	errs := make(chan error)
	54	calls := make(chan struct{}, 1)
	55	go watchLoop(ctx, events, errs, func(string) error { return nil }, 50*time.Millisecond, func() { calls <- struct{}{} })
	56
	57	errs <- fsnotify.ErrEventOverflow
	58	expectCall(t, calls, "event overflow")
	59	}

Commit c097185877

Commit `c097185877`