use a fresh spooldb session per image instead of a shared one

main.go

@@ -71,11 +71,8 @@ func main() {
 	}
 	slog.Debug("claude auth", "mechanism", auth.Name())
 
-	sp := &spoolSync{}
-	defer sp.close()
-
 	if *serveAddr != "" {
-		if err := serve(*serveAddr, auth, sp, *dryRun); err != nil {
+		if err := serve(*serveAddr, auth, *dryRun); err != nil {
 			fail("serve: %v", err)
 		}
 		return
@@ -87,7 +84,7 @@ func main() {
 	}
 	results := make([]result, 0, flag.NArg())
 	for _, path := range flag.Args() {
-		results = append(results, processImage(path, auth, sp, *dryRun))
+		results = append(results, processImage(path, auth, *dryRun))
 	}
 
 	enc := json.NewEncoder(os.Stdout)
@@ -95,50 +92,43 @@ func main() {
 	enc.Encode(results)
 }
 
-// spoolSync lazily logs into spooldb on first use, so its (slow) browser login
-// overlaps with the first image's weight read rather than blocking it. Every
-// site interaction is best-effort: failures are logged and the corresponding
-// output fields are simply omitted.
-type spoolSync struct {
-	once   sync.Once
+// spoolSession is a fresh, logged-in spooldb session used for a single image:
+// it owns one headless browser, does the read and the maybe-write, then closes.
+// Every site interaction is best-effort — failures are logged and the
+// corresponding output fields are simply omitted.
+type spoolSession struct {
 	client *spooldb.Client
-	err    error
 }
 
-func (s *spoolSync) login() (*spooldb.Client, error) {
-	s.once.Do(func() {
-		user, pass := os.Getenv("SPOOLDB_USER"), os.Getenv("SPOOLDB_PASS")
-		if user == "" || pass == "" {
-			s.err = fmt.Errorf("SPOOLDB_USER/SPOOLDB_PASS not set")
-			return
-		}
-		c, err := spooldb.New()
-		if err != nil {
-			s.err = err
-			return
-		}
-		ctx, cancel := context.WithTimeout(context.Background(), 90*time.Second)
-		defer cancel()
-		if err := c.Login(ctx, user, pass); err != nil {
-			c.Close()
-			s.err = fmt.Errorf("login: %w", err)
-			return
-		}
-		s.client = c
-	})
-	return s.client, s.err
+// openSpoolSession launches a browser and logs into spooldb. It returns nil (and
+// logs) if credentials are missing or login fails, so the caller can carry on
+// with just the weight read.
+func openSpoolSession() *spoolSession {
+	user, pass := os.Getenv("SPOOLDB_USER"), os.Getenv("SPOOLDB_PASS")
+	if user == "" || pass == "" {
+		slog.Warn("spooldb: skipping (SPOOLDB_USER/SPOOLDB_PASS not set)")
+		return nil
+	}
+	c, err := spooldb.New()
+	if err != nil {
+		slog.Warn("spooldb: skipping (browser launch failed)", "err", err)
+		return nil
+	}
+	ctx, cancel := context.WithTimeout(context.Background(), 90*time.Second)
+	defer cancel()
+	if err := c.Login(ctx, user, pass); err != nil {
+		c.Close()
+		slog.Warn("spooldb: skipping (login failed)", "err", err)
+		return nil
+	}
+	return &spoolSession{client: c}
 }
 
 // info reads the spool's current location and weights, or nil if unavailable.
-func (s *spoolSync) info(spoolID string) *spooldb.SpoolInfo {
-	client, err := s.login()
-	if err != nil {
-		slog.Warn("spooldb: skipping spool lookup", "err", err)
-		return nil
-	}
-	ctx, cancel := context.WithTimeout(context.Background(), 60*time.Second)
+func (s *spoolSession) info(spoolID string) *spooldb.SpoolInfo {
+	ctx, cancel := context.WithTimeout(context.Background(), 90*time.Second)
 	defer cancel()
-	info, err := client.SpoolInfo(ctx, spoolID)
+	info, err := s.client.SpoolInfo(ctx, spoolID)
 	if err != nil {
 		slog.Warn("spooldb: lookup failed", "spool", spoolID, "err", err)
 		return nil
@@ -147,22 +137,17 @@ func (s *spoolSync) info(spoolID string) *spooldb.SpoolInfo {
 }
 
 // setTotal writes a new total (with-spool) weight back to the site.
-func (s *spoolSync) setTotal(spoolID string, grams float64) bool {
-	client, err := s.login()
-	if err != nil {
-		slog.Warn("spooldb: skipping weight update", "err", err)
-		return false
-	}
+func (s *spoolSession) setTotal(spoolID string, grams float64) bool {
 	ctx, cancel := context.WithTimeout(context.Background(), 90*time.Second)
 	defer cancel()
-	if err := client.SetTotalWeight(ctx, spoolID, grams); err != nil {
+	if err := s.client.SetTotalWeight(ctx, spoolID, grams); err != nil {
 		slog.Warn("spooldb: weight update failed", "spool", spoolID, "err", err)
 		return false
 	}
 	return true
 }
 
-func (s *spoolSync) close() {
+func (s *spoolSession) close() {
 	if s.client != nil {
 		s.client.Close()
 	}
@@ -170,17 +155,17 @@ func (s *spoolSync) close() {
 
 // processImage reads one photo, capturing any failure in the result's Error
 // field so a single bad image doesn't abort the whole batch.
-func processImage(path string, auth claude.Auth, sp *spoolSync, dryRun bool) result {
+func processImage(path string, auth claude.Auth, dryRun bool) result {
 	img, err := loadImage(path)
 	if err != nil {
 		return result{Image: path, Error: fmt.Sprintf("load image: %v", err)}
 	}
-	return processImg(img, path, auth, sp, dryRun)
+	return processImg(img, path, auth, dryRun)
 }
 
 // processImg runs the QR + weight + spooldb logic on a decoded image. name is
 // just a label for the output (a file path or upload filename).
-func processImg(img image.Image, name string, auth claude.Auth, sp *spoolSync, dryRun bool) result {
+func processImg(img image.Image, name string, auth claude.Auth, dryRun bool) result {
 	defer trace("image " + name)()
 	r := result{Image: name}
 
@@ -196,18 +181,25 @@ func processImg(img image.Image, name string, auth claude.Auth, sp *spoolSync, d
 	r.SpoolID = spoolID(url)
 	r.URL = url
 
-	// Read the spool's current location/weight from the site concurrently with
-	// the (slower) weight read off the photo.
+	// Open a fresh spooldb session and read the spool's current location/weight,
+	// concurrently with the (slower) weight read off the photo. The same session
+	// is reused for the maybe-write below, then closed.
+	var sess *spoolSession
 	var info *spooldb.SpoolInfo
 	var wg sync.WaitGroup
 	wg.Add(1)
 	go func() {
 		defer wg.Done()
-		info = sp.info(r.SpoolID)
+		if sess = openSpoolSession(); sess != nil {
+			info = sess.info(r.SpoolID)
+		}
 	}()
 
 	reading, err := claude.ReadWeight(img, auth)
 	wg.Wait()
+	if sess != nil {
+		defer sess.close()
+	}
 	if info != nil {
 		r.Location = info.Location
 		r.PreviousWeight = &weightBreakdown{
@@ -246,7 +238,7 @@ func processImg(img image.Image, name string, auth claude.Auth, sp *spoolSync, d
 		if dryRun {
 			slog.Info("spooldb: would update", "spool", r.SpoolID,
 				"remaining_from", info.RemainingGrams, "remaining_to", newRemaining, "measured_total", reading.Weight)
-		} else if sp.setTotal(r.SpoolID, reading.Weight) {
+		} else if sess.setTotal(r.SpoolID, reading.Weight) {
 			updated = true
 			slog.Info("spooldb: updated", "spool", r.SpoolID,
 				"remaining_from", info.RemainingGrams, "remaining_to", newRemaining, "measured_total", reading.Weight)