Clean connector tracker after each access block to stop memory leaks (#9305)

Immediately clean connectors which the client side does not know about

Fixes #9303

3 files changed, 130 insertions, 5 deletions

diff --git a/uitest/src/main/java/com/vaadin/tests/application/MissingHierarchyDetection.java b/uitest/src/main/java/com/vaadin/tests/application/MissingHierarchyDetection.java
index 8f35d69112..54c19c3353 100644
--- a/uitest/src/main/java/com/vaadin/tests/application/MissingHierarchyDetection.java
+++ b/uitest/src/main/java/com/vaadin/tests/application/MissingHierarchyDetection.java
@@ -15,8 +15,16 @@
  */
 package com.vaadin.tests.application;
 
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import java.util.logging.Handler;
+import java.util.logging.LogRecord;
+import java.util.logging.Logger;
+
 import com.vaadin.server.VaadinRequest;
-import com.vaadin.tests.components.AbstractReindeerTestUI;
+import com.vaadin.server.VaadinService;
+import com.vaadin.tests.components.AbstractReindeerTestUIWithLog;
 import com.vaadin.ui.Button;
 import com.vaadin.ui.Button.ClickEvent;
 import com.vaadin.ui.Component;
@@ -24,13 +32,15 @@ import com.vaadin.ui.CssLayout;
 import com.vaadin.ui.Label;
 import com.vaadin.ui.SelectiveRenderer;
 
-public class MissingHierarchyDetection extends AbstractReindeerTestUI {
+public class MissingHierarchyDetection extends AbstractReindeerTestUIWithLog {
 
     private boolean isChildRendered = true;
     private BrokenCssLayout brokenLayout = new BrokenCssLayout();
 
     private CssLayout normalLayout = new CssLayout(
             new Label("Normal layout child"));
+    private List<LogRecord> pendingErrors = Collections
+            .synchronizedList(new ArrayList<>());
 
     public class BrokenCssLayout extends CssLayout
             implements SelectiveRenderer {
@@ -49,6 +59,29 @@ public class MissingHierarchyDetection extends AbstractReindeerTestUI {
 
     @Override
     protected void setup(VaadinRequest request) {
+        // Catch log messages so we can see if there is an error
+        Logger vaadinServiceLogger = Logger
+                .getLogger(VaadinService.class.getName());
+        vaadinServiceLogger.addHandler(new Handler() {
+
+            @Override
+            public void publish(LogRecord record) {
+                if (record.getThrown() instanceof AssertionError) {
+                    pendingErrors.add(record);
+                    vaadinServiceLogger.removeHandler(this);
+                }
+            }
+
+            @Override
+            public void flush() {
+
+            }
+
+            @Override
+            public void close() throws SecurityException {
+
+            }
+        });
         addComponent(brokenLayout);
         addComponent(normalLayout);
         addComponent(new Button("Toggle properly", new Button.ClickListener() {
@@ -64,6 +97,16 @@ public class MissingHierarchyDetection extends AbstractReindeerTestUI {
                         toggle(false);
                     }
                 }));
+        addComponent(new Button("Check for errors", new Button.ClickListener() {
+            @Override
+            public void buttonClick(ClickEvent event) {
+                if (!pendingErrors.isEmpty()) {
+                    log(pendingErrors.remove(0).getThrown().getMessage());
+                } else {
+                    log("No errors");
+                }
+            }
+        }));
     }
 
     private void toggle(boolean properly) {
diff --git a/uitest/src/main/java/com/vaadin/tests/components/ui/ConnectorTrackerMemoryLeakUI.java b/uitest/src/main/java/com/vaadin/tests/components/ui/ConnectorTrackerMemoryLeakUI.java
new file mode 100644
index 0000000000..fdcfe24776
--- /dev/null
+++ b/uitest/src/main/java/com/vaadin/tests/components/ui/ConnectorTrackerMemoryLeakUI.java
@@ -0,0 +1,78 @@
+package com.vaadin.tests.components.ui;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import com.vaadin.server.VaadinRequest;
+import com.vaadin.ui.Button;
+import com.vaadin.ui.CssLayout;
+import com.vaadin.ui.Label;
+import com.vaadin.ui.UI;
+import com.vaadin.ui.VerticalLayout;
+import com.vaadin.ui.Window;
+
+public class ConnectorTrackerMemoryLeakUI extends UI {
+
+    public static final String BUTTON_CAPTION = "Kill!";
+    public static final String LABEL_STOPPED = "Still alive!";
+    private CssLayout panel = new CssLayout();
+    private List<String> items = new ArrayList<>(200);
+    private VerticalLayout layout = new VerticalLayout();
+
+    @Override
+    protected void init(VaadinRequest vaadinRequest) {
+
+        Button button = new Button(BUTTON_CAPTION);
+        button.addClickListener(e -> {
+            gc();
+            long memory = Runtime.getRuntime().totalMemory();
+            System.out.println("Before: " + memory);
+            // To simulate 200 concurrent session we do this 200 times
+            for (int i = 0; i < 200; i++) {
+
+                // Clear items
+                items.clear();
+                for (int j = 1; j <= 200; j++) {
+
+                    // Add one item and update the panel with those
+                    items.add("Item #" + j);
+                    updatePanel(panel, items);
+                }
+            }
+
+            // We made it this far. Good for us.
+            Label labelStop = new Label(LABEL_STOPPED);
+            layout.addComponent(labelStop);
+            gc();
+            long delta = Runtime.getRuntime().totalMemory() - memory;
+            memory = memory + delta;
+            System.out.println(" After: " + memory + " (+" + delta + ")");
+        });
+
+        layout.addComponents(button, panel);
+        setContent(layout);
+    }
+
+    private void gc() {
+        // Sometimes the VM needs a couple of "suggestions" to actually
+        // perform gc. There is no automated test for this UI so tweak if
+        // needed.
+        for (int i = 0; i < 3; i++) {
+            Runtime.getRuntime().gc();
+        }
+
+        try {
+            Thread.sleep(500);
+        } catch (InterruptedException e1) {
+        }
+    }
+
+    private static void updatePanel(CssLayout panel, List<String> items) {
+        panel.removeAllComponents();
+        items.forEach(i -> panel.addComponent(new Button(i, e -> {
+            Window w = new Window();
+            UI.getCurrent().addWindow(w);
+        })));
+    }
+
+}
diff --git a/uitest/src/test/java/com/vaadin/tests/application/MissingHierarchyDetectionTest.java b/uitest/src/test/java/com/vaadin/tests/application/MissingHierarchyDetectionTest.java
index 2a97dbaaf6..80eb0735da 100644
--- a/uitest/src/test/java/com/vaadin/tests/application/MissingHierarchyDetectionTest.java
+++ b/uitest/src/test/java/com/vaadin/tests/application/MissingHierarchyDetectionTest.java
@@ -41,10 +41,14 @@ public class MissingHierarchyDetectionTest extends SingleBrowserTest {
         assertNoSystemNotifications();
         Assert.assertTrue(isElementPresent(LabelElement.class));
 
-        ButtonElement toggleInproperly = $(ButtonElement.class)
+        ButtonElement toggleImproperly = $(ButtonElement.class)
                 .caption("Toggle improperly").first();
-        toggleInproperly.click();
+        toggleImproperly.click();
 
-        assertSystemNotification();
+        $(ButtonElement.class).caption("Check for errors").first().click();
+        Assert.assertTrue(
+                "No error was logged for the missing hierarchy change event",
+                getLogRow(0).contains(
+                        "is no longer visible to the client, but no corresponding hierarchy change was sent."));
     }
 }