1 files changed, 106 insertions, 0 deletions
diff --git a/statistics/src/main/java/com/yahoo/statistics/Handle.java b/statistics/src/main/java/com/yahoo/statistics/Handle.java
new file mode 100644
index 00000000000..6c3d94dad41
--- /dev/null
+++ b/statistics/src/main/java/com/yahoo/statistics/Handle.java
@@ -0,0 +1,106 @@
+// Copyright 2016 Yahoo Inc. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
+package com.yahoo.statistics;
+
+
+import java.util.TimerTask;
+
+
+/**
+ * Base class for the interface to the statistics framework.
+ *
+ * @author  <a href="mailto:steinar@yahoo-inc.com">Steinar Knutsen</a>
+ */
+public abstract class Handle {
+
+    private TimerTask task;
+
+    private final String name;
+    private boolean cancelled;
+    private final Statistics manager;
+    private final Callback parametrizedCallback;
+    private boolean firstTime;
+
+    Handle(String name, Statistics manager, Callback parametrizedCallback) {
+        this.name = name;
+        this.manager = manager;
+        this.parametrizedCallback = parametrizedCallback;
+        firstTime = true;
+    }
+
+    String getName() {
+        return name;
+    }
+
+    TimerTask makeTask() {
+        final Handle self = this;
+        synchronized (self) {
+            if (task != null) {
+                task.cancel();
+            }
+            task = new TimerTask() {
+                public void run() {
+                    self.run();
+                }
+            };
+            return task;
+        }
+    }
+
+    /**
+     * Run the callback object.
+     *
+     * This will happen at the start of each invocation of a Handle's
+     * run() method. The callback is presumed to be exception safe.
+     * If no callback is set, this is a no-op. The callback will need
+     * to handle any necessary synchronization itself.
+     */
+    public final void runCallback() {
+        if (parametrizedCallback == null) {
+            return;
+        }
+        parametrizedCallback.run(this, firstTime);
+        firstTime = false;
+    }
+
+    /**
+     * Run the callback object first, then invoke runHandle().
+     */
+    public final void run() {
+        runCallback();
+        runHandle();
+    }
+
+    /**
+     * Invoke an action to be performed periodically for a statistics Handle.
+     *
+     * <p>Synchronization has to be handled by the method itself.
+     */
+    public abstract void runHandle();
+
+    /**
+     * Cancel this Handle and remove it from internal state in Statistics.
+     *
+     * @return value of java.util.TimerTask.cancel()
+     */
+    public final boolean cancel() {
+        boolean ok = (task == null ? false : task.cancel());
+        cancelled = true;
+        manager.purge();
+        return ok;
+    }
+
+    /**
+     * Returns whether this object has been cancelled or not.
+     *
+     * @return true if cancelled
+     */
+    public final boolean isCancelled() {
+        return cancelled;
+    }
+
+    @Override
+    public abstract boolean equals(Object o);
+
+    @Override
+    public abstract int hashCode();
+}