Avoid leaking memory from inherited ThreadLocales. Fixes #12401

The issue is fixed by changing the normal HashMap inside the inheritable
thread local to a map implementation holding only weak references to the
values (WeakValueMap).

Also included is a test UI that starts threads, which run until the JVM
is quit. This along with VisualVM was used to reproduce the issue and
verify the fix.

Change-Id: I116cc4e56e8a19c3b770abab6b18b9e262f4dafa

1 files changed, 57 insertions, 0 deletions

diff --git a/uitest/src/com/vaadin/tests/performance/ThreadMemoryLeaksTest.java b/uitest/src/com/vaadin/tests/performance/ThreadMemoryLeaksTest.java
new file mode 100644
index 0000000000..5ffc7141af
--- /dev/null
+++ b/uitest/src/com/vaadin/tests/performance/ThreadMemoryLeaksTest.java
@@ -0,0 +1,57 @@
+package com.vaadin.tests.performance;
+
+import java.util.Date;
+import java.util.Timer;
+import java.util.TimerTask;
+
+import com.vaadin.server.VaadinRequest;
+import com.vaadin.tests.components.AbstractTestUI;
+import com.vaadin.ui.Button;
+import com.vaadin.ui.Label;
+
+public class ThreadMemoryLeaksTest extends AbstractTestUI {
+
+    public static class Worker {
+        long value = 0;
+        private TimerTask task = new TimerTask() {
+            @Override
+            public void run() {
+                value++;
+            }
+        };
+        private final Timer timer = new Timer(true);
+
+        public Worker() {
+            timer.scheduleAtFixedRate(task, new Date(), 1000);
+        }
+    }
+
+    int workers = 0;
+    Label label;
+
+    @Override
+    protected void setup(VaadinRequest request) {
+        label = new Label(String.format("%d workers", workers));
+        addComponent(label);
+        addComponent(new Button("Add worker", new Button.ClickListener() {
+            @Override
+            public void buttonClick(Button.ClickEvent event) {
+                new Worker();
+                workers++;
+                label.setValue(String.format("%d workers", workers));
+            }
+        }));
+    }
+
+    @Override
+    protected String getTestDescription() {
+        return "Inherited ThreadLocals should not leak memory. Clicking the "
+                + "button starts a new thread, after which memory consumption "
+                + "can be checked with visualvm";
+    }
+
+    @Override
+    protected Integer getTicketNumber() {
+        return 12401;
+    }
+}