Updating JavaFX BarChart data causes memory leak

Question

I've discovered what I believe is a memory leak in JavaFX (1.8u40 GA and 1.8u60 b10 EA) BarChart triggered by replacing all the data values in the series. This is exasperated by our application which does this several times a second.

Using jvisualvm shows an uncontrolled growth in the number of javafx.scene.layout.StackPane instances which eventually results in an OutOfMemoryError. Styled StackPane nodes are used internally by BarChart for the bars.

I've tried a different strategies to update the list. All exhibit the same issue.

// 1
series.getData().clear();
series.getData().addAll(list);
// 2
series.getData().setAll(list);
// 3
series.setData(list)

Interestingly the example in the Oracle BarChart tutorial updates values by adding all the bars/points first, and then mutating them using XYChart.Data.setYValue() . This could work, but is not convenient for us as the number of data points can vary dynamically.

Specific questions

• Is there anyway to avoid this issue, other than a extra logic using the setYValue() approach above.
• Have I stumbled across an actual memory leak in JavaFX? or just an artefact of my misuse of the API? Surely freeing internal nodes when data is updated is JavaFX responsibility

Example

public class ChartUpdate extends Application {
    private int clock;
    public static void main(String[] args) {
        launch(args);
    }
    @Override
    public void start(Stage stage) {
        CategoryAxis xAxis = new CategoryAxis();
        NumberAxis yAxis = new NumberAxis(0, 100, 10);
        yAxis.setAutoRanging(false);
        BarChart<String, Number> graph = new BarChart<>(xAxis, yAxis);
        graph.setAnimated(false);
        Series<String, Number> series = new Series<>();
        graph.getData().add(series);
        stage.setScene(new Scene(graph));
        stage.show();

        Timeline timeLine = new Timeline();
        timeLine.getKeyFrames().add(
                new KeyFrame(Duration.millis(500),
                        (e) -> {
                            ObservableList<Data<String, Number>> list = FXCollections.observableArrayList();
                            for (int i = 0; i < 100; i++) {
                                list.add(new Data<>(String.valueOf(i), (clock + i) % 100));
                            }
                            series.setData(list);
                            clock++;
                        }));
        timeLine.setCycleCount(Animation.INDEFINITE);
        timeLine.play();
    }
}

• Update (16th April 2015) Raised https://bugs.openjdk.java.net/browse/JDK-8094805 and posted to OpenJFX mailing list

Answer 1

In summary this was a genuine issue accepted by JavaFX team and fixed by JDK-8094805 in 8u60

See https://bugs.openjdk.java.net/browse/JDK-8094805 for more detail.