Log error if node-id file can not be written

common/helper.go

@@ -80,17 +80,7 @@ func GetCollectorId(collectorId string) string {
 	id := collectorId
 	if strings.HasPrefix(collectorId, "file:") {
 		filePath := strings.SplitAfterN(collectorId, ":", 2)[1]
-		err := FileExists(filePath)
-		if err != nil {
-			log.Info("node-id file doesn't exist, generating a new one")
-			CreatePathToFile(filePath)
-			ioutil.WriteFile(filePath, []byte(RandomUuid()), 0644)
-		}
-		file, err := ioutil.ReadFile(filePath)
-		if err != nil {
-			log.Fatal("Can not read node-id file: ", err)
-		}
-		id = strings.Trim(string(file), " \n")
+		id = idFromFile(filePath)
 	}
 
 	if id != "" && !cfgfile.ValidateConfig() {
@@ -99,6 +89,25 @@ func GetCollectorId(collectorId string) string {
 	return id
 }
 
+func idFromFile(filePath string) string {
+	err := FileExists(filePath)
+	if err != nil {
+		log.Info("node-id file doesn't exist, generating a new one")
+		err = CreatePathToFile(filePath)
+		if err == nil {
+			err = ioutil.WriteFile(filePath, []byte(RandomUuid()), 0644)
+			log.Error("Can not write node-id file: ", err)
+		}
+	}
+
+	file, err := ioutil.ReadFile(filePath)
+	if err != nil {
+		log.Error("Can not read node-id file: ", err)
+		return ""
+	}
+	return strings.Trim(string(file), " \n")
+}
+
 func RandomUuid() string {
 	return uuid.NewRandom().String()
 }

common/helper_test.go

@@ -64,6 +64,27 @@ func TestGetCollectorIdFromNonExistingFile(t *testing.T) {
 	}
 }
 
+func TestCollectorIdFileNotWritable(t *testing.T) {
+	dir, err := ioutil.TempDir("", "test-node-id")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(dir)
+
+	nodeIdDir := filepath.Join(dir, "non-writable")
+
+	err = os.MkdirAll(nodeIdDir, 0500)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	tmpfile := filepath.Join(nodeIdDir, "node-id")
+	result := GetCollectorId("file:/" + tmpfile)
+	if result != "" {
+		t.Fatalf("Unwritable node-id file should result in empty node-id")
+	}
+}
+
 func TestEncloseWithWithoutAction(t *testing.T) {
 	content := "/some regex/"
 	result := EncloseWith(content, "/")