CURATOR-549

The next phase of this issue will implement a bridge cache that bridges TreeCache for pre 3.6 SK and CuratorCache for ZK 3.6+. That bridge will need this TreeCache iterator.

curator-recipes/src/main/java/org/apache/curator/framework/recipes/cache/TreeCache.java

@@ -47,6 +47,7 @@
 import java.io.Closeable;
 import java.util.ArrayList;
 import java.util.Collections;
+import java.util.Iterator;
 import java.util.LinkedList;
 import java.util.List;
 import java.util.Map;
@@ -217,7 +218,7 @@ public static Builder newBuilder(CuratorFramework client, String path)
 
     private static final ChildData DEAD = new ChildData("/", null, null);
 
-    private static boolean isLive(ChildData cd)
+    static boolean isLive(ChildData cd)
     {
         return cd != null && cd != DEAD;
     }
@@ -226,7 +227,7 @@ private static boolean isLive(ChildData cd)
 
     private static final AtomicReferenceFieldUpdater<TreeNode, ConcurrentMap<String, TreeNode>> childrenUpdater = (AtomicReferenceFieldUpdater)AtomicReferenceFieldUpdater.newUpdater(TreeNode.class, ConcurrentMap.class, "children");
 
-    private final class TreeNode implements Watcher, BackgroundCallback
+    final class TreeNode implements Watcher, BackgroundCallback
     {
         volatile ChildData childData;
         final TreeNode parent;
@@ -343,7 +344,7 @@ void wasDeleted() throws Exception
 
             if ( isLive(oldChildData) )
             {
-                publishEvent(TreeCacheEvent.Type.NODE_REMOVED, oldChildData);
+                publishEvent(TreeCacheEvent.Type.NODE_REMOVED, oldChildData, null);
             }
 
             if ( parent == null )
@@ -482,7 +483,14 @@ else if ( event.getResultCode() == KeeperException.Code.NONODE.intValue() )
                         }
                         if ( childDataUpdater.compareAndSet(this, oldChildData, toUpdate) )
                         {
-                            publishEvent(isLive(oldChildData) ? TreeCacheEvent.Type.NODE_UPDATED : TreeCacheEvent.Type.NODE_ADDED, toPublish);
+                            if ( isLive(oldChildData) )
+                            {
+                                publishEvent(TreeCacheEvent.Type.NODE_UPDATED, toPublish, oldChildData);
+                            }
+                            else
+                            {
+                                publishEvent(TreeCacheEvent.Type.NODE_ADDED, toPublish, null);
+                            }
                             break;
                         }
                     }
@@ -750,6 +758,49 @@ public ChildData getCurrentData(String fullPath)
         return isLive(result) ? result : null;
     }
 
+    /**
+     * Return an iterator over all nodes in the cache. There are no
+     * guarantees of accuracy; this is merely the most recent view of the data.
+     *
+     * @return a possibly-empty iterator of nodes in the cache
+     */
+    public Iterator<ChildData> iterator()
+    {
+        return new TreeCacheIterator(root);
+    }
+
+    /**
+     * Return the number of nodes in the cache. There are no
+     * guarantees of accuracy; this is merely the most recent view of the data.
+     *
+     * @return size
+     */
+    public int size()
+    {
+        return size(root);
+    }
+
+    private int size(TreeNode node)
+    {
+        int size;
+        if ( isLive(node.childData) )
+        {
+            size = 1;
+            if ( node.children != null )
+            {
+                for ( TreeNode child : node.children.values() )
+                {
+                    size += size(child);
+                }
+            }
+        }
+        else
+        {
+            size = 0;
+        }
+        return size;
+    }
+
     private void callListeners(final TreeCacheEvent event)
     {
         listeners.forEach(listener ->
@@ -837,9 +888,9 @@ private void publishEvent(TreeCacheEvent.Type type)
         publishEvent(new TreeCacheEvent(type, null));
     }
 
-    private void publishEvent(TreeCacheEvent.Type type, ChildData data)
+    private void publishEvent(TreeCacheEvent.Type type, ChildData data, ChildData oldData)
     {
-        publishEvent(new TreeCacheEvent(type, data));
+        publishEvent(new TreeCacheEvent(type, data, oldData));
     }
 
     private void publishEvent(final TreeCacheEvent event)

curator-recipes/src/main/java/org/apache/curator/framework/recipes/cache/TreeCacheEvent.java

@@ -26,6 +26,7 @@
 {
     private final Type type;
     private final ChildData data;
+    private final ChildData oldData;
 
     /**
      * Type of change
@@ -112,9 +113,20 @@
      * @param data event data or null
      */
     public TreeCacheEvent(Type type, ChildData data)
+    {
+        this(type, data, null);
+    }
+
+    /**
+     * @param type event type
+     * @param data event data or null
+     * @param oldData event oldData or null
+     */
+    public TreeCacheEvent(Type type, ChildData data, ChildData oldData)
     {
         this.type = type;
         this.data = data;
+        this.oldData = oldData;
     }
 
     /**
@@ -133,6 +145,14 @@ public ChildData getData()
         return data;
     }
 
+    /**
+     * @return the node's old data when the type is {@link org.apache.curator.framework.recipes.cache.TreeCacheEvent.Type#NODE_UPDATED}
+     */
+    public ChildData getOldData()
+    {
+        return oldData;
+    }
+
     @Override
     public String toString()
     {

curator-recipes/src/main/java/org/apache/curator/framework/recipes/cache/TreeCacheIterator.java

@@ -0,0 +1,101 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing,
+ * software distributed under the License is distributed on an
+ * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+ * KIND, either express or implied.  See the License for the
+ * specific language governing permissions and limitations
+ * under the License.
+ */
+package org.apache.curator.framework.recipes.cache;
+
+import com.google.common.collect.Iterators;
+import java.util.Iterator;
+import java.util.LinkedList;
+import java.util.NoSuchElementException;
+
+// depth first iterator over tree cache nodes
+class TreeCacheIterator implements Iterator<ChildData>
+{
+    private final LinkedList<Current> stack = new LinkedList<>();
+    private Current current;
+
+    private static class Current
+    {
+        final Iterator<TreeCache.TreeNode> iterator;
+        TreeCache.TreeNode node;
+
+        Current(Iterator<TreeCache.TreeNode> iterator)
+        {
+            this.iterator = iterator;
+            node = iterator.next();
+        }
+    }
+
+    TreeCacheIterator(TreeCache.TreeNode root)
+    {
+        current = new Current(Iterators.forArray(root));
+        stack.push(current);
+    }
+
+    @Override
+    public boolean hasNext()
+    {
+        return (current != null) && TreeCache.isLive(current.node.childData);
+    }
+
+    @Override
+    public ChildData next()
+    {
+        if ( current == null )
+        {
+            throw new NoSuchElementException();
+        }
+
+        ChildData result = current.node.childData;  // result of next iteration is current node's data
+
+        // set the next node for the next iteration (or note completion)
+
+        do
+        {
+            setNext();
+        } while ( (current != null) && !TreeCache.isLive(current.node.childData) );
+
+        return result;
+    }
+
+    private void setNext()
+    {
+        if ( current.node.children != null )
+        {
+            stack.push(current);
+            current = new Current(current.node.children.values().iterator());
+        }
+        else while ( true )
+        {
+            if ( current.iterator.hasNext() )
+            {
+                current.node = current.iterator.next();
+                break;
+            }
+            else if ( stack.size() > 0 )
+            {
+                current = stack.pop();
+            }
+            else
+            {
+                current = null; // done
+                break;
+            }
+        }
+    }
+}

curator-recipes/src/test/java/org/apache/curator/framework/recipes/cache/BaseTestTreeCache.java

@@ -193,6 +193,16 @@ TreeCacheEvent assertEvent(TreeCacheEvent.Type expectedType, String expectedPath
         {
             Assert.assertEquals(event.getData().getData(), expectedData, message);
         }
+
+        if ( event.getType() == TreeCacheEvent.Type.NODE_UPDATED)
+        {
+            Assert.assertNotNull(event.getOldData());
+        }
+        else
+        {
+            Assert.assertNull(event.getOldData());
+        }
+
         return event;
     }
 }