Give the Service its own fetch client and open-document waits instead of reading package variables from background goroutines, which a test or reload changed meanwhile: data races under -race (issue 1601)

modules/brother/cmd/brother/glass_test.go

@@ -264,7 +264,7 @@ func TestAnOpenDocumentIsFoundAgainAfterARestartAndItsPagesAreDeletedWhenClosed(
 	docExpiry = 200 * time.Millisecond
 	t.Cleanup(func() { docExpiry = old })
 	s := &Service{Settings: Settings{Scanner: f.base(), Folder: folder, Resolution: 200, ColorMode: "color"}, Now: func() time.Time { return fixedNow },
-		Asks: askBus, AnswerWait: 5 * time.Second, ScanWait: 5 * time.Second, AnswerPoll: 5 * time.Millisecond, Jobs: NewJobs()}
+		Asks: askBus, AnswerWait: 5 * time.Second, ScanWait: 5 * time.Second, AnswerPoll: 5 * time.Millisecond, Jobs: NewJobs(), Fetch: fetchClient, DocExpiry: docExpiry}
 	if err := s.Recover(context.Background()); err != nil {
 		t.Fatal(err)
 	}

modules/brother/cmd/brother/main.go

@@ -112,7 +112,7 @@ func tools(settingsFile string, now func() time.Time) []stdio.Tool {
 		}
 		return &Service{Settings: s, Node: os.Getenv("MESH_NODE"), Now: now, Asks: askBus,
 			AnswerWait: answerWait, ScanWait: scanWait, AnswerPoll: answerPoll,
-			QuickWait: quickWait, FeederWait: feederWait, Jobs: jobs, Upload: uploadVia,
+			QuickWait: quickWait, FeederWait: feederWait, Jobs: jobs, Upload: uploadVia, Fetch: fetchClient, DocExpiry: docExpiry, DocRetry: docRetry,
 			Bucket: func() (string, error) { return ReadBucket(os.Getenv("BROTHER_BUCKET")) }}, nil
 	}
 	// ask is a tool that reads its arguments, and answers what the service gives.

modules/brother/cmd/brother/scan.go

@@ -34,8 +34,13 @@ type Service struct {
 	Jobs *Jobs
 	// Upload asks a machine's node-files to send one of its files into the bucket and answers the key; Bucket is
 	// brother's bucket. Both are the tool side's (printer.print with path and node).
-	Upload func(node, path, bucket string) (string, error)
+	// Fetch reads the links the device process signs; DocExpiry and DocRetry are the open documents' waits. They are
-	Bucket func() (string, error)
+	// copied into the Service when it is made, because background work reads them while a test (or a reload) changes the
+	// package's own, which would race.
+	Fetch               *http.Client
+	DocExpiry, DocRetry time.Duration
+	Upload              func(node, path, bucket string) (string, error)
+	Bucket              func() (string, error)
 }
 
 // Jobs are the scans this tool process has started and not yet been asked the outcome of. A scan runs in the
@@ -236,7 +241,7 @@ func (s *Service) finishScan(ctx context.Context, id string, wait time.Duration,
 	}
 	if doc, _ := ans["document"].(string); doc != "" && ans["key"] == nil {
 		// A page was added to an open document: nothing to file yet, and the document is closed if it is left open.
-		s.armDocument(doc, docExpiry, 0)
+		s.armDocument(doc, s.docExpiry(), 0)
 		return ans, nil
 	}
 	if ask.Document != "" && ask.Finish {
@@ -296,7 +301,7 @@ func (s *Service) fileOne(ctx context.Context, ans map[string]any) (map[string]a
 	var buf bytes.Buffer
 	gctx, cancel := context.WithTimeout(ctx, 5*time.Minute)
 	defer cancel()
-	if _, err := objectlink.Get(gctx, fetchClient, link, &buf, objectlink.MaxDocument, sum); err != nil {
+	if _, err := objectlink.Get(gctx, s.fetchClient(), link, &buf, objectlink.MaxDocument, sum); err != nil {
 		return nil, fmt.Errorf("the scan is kept as %s, but it could not be read from the store: %w", key, err)
 	}
 	pdf := buf.Bytes()
@@ -329,7 +334,28 @@ func withoutLink(ans map[string]any) map[string]any {
 	return out
 }
 
-// fetchClient reads the links the device process signs; a test puts a client of its own in its place.
+func (s *Service) fetchClient() *http.Client {
+	if s.Fetch != nil {
+		return s.Fetch
+	}
+	return &http.Client{}
+}
+
+func (s *Service) docExpiry() time.Duration {
+	if s.DocExpiry > 0 {
+		return s.DocExpiry
+	}
+	return 30 * time.Minute
+}
+
+func (s *Service) docRetry() time.Duration {
+	if s.DocRetry > 0 {
+		return s.DocRetry
+	}
+	return 5 * time.Minute
+}
+
+// fetchClientDefault is what a Service made by the tools reads the links with; a test puts a client of its own in its place before it makes the tools.
 var fetchClient = &http.Client{}
 
 // ScanStatus says whether the scanner answers, and what it is doing. A scanner that does not answer is an
@@ -370,7 +396,7 @@ func (s *Service) armDocument(doc string, d time.Duration, attempts int) {
 		if err == nil || attempts >= 10 || strings.Contains(err.Error(), "is closed already") || strings.Contains(err.Error(), "its id is wrong") {
 			return
 		}
-		s.armDocument(doc, docRetry, attempts+1)
+		s.armDocument(doc, s.docRetry(), attempts+1)
 	})
 }
 
@@ -388,9 +414,9 @@ func (s *Service) Recover(ctx context.Context) error {
 		if id == "" {
 			continue
 		}
-		left := docExpiry
+		left := s.docExpiry()
 		if at, err := time.Parse(time.RFC3339, fmt.Sprint(m["updated"])); err == nil {
-			left = max(docExpiry-s.Now().Sub(at), time.Second)
+			left = max(s.docExpiry()-s.Now().Sub(at), time.Second)
 		}
 		s.armDocument(id, left, 0)
 	}