[GitHub] [helix] desaikomal commented on a diff in pull request #2439: Add a Trie class to represent RecursivePersistWatcherListener in ZkClient

["desaikomal (via GitHub)" <gi...@apache.org>]

desaikomal commented on code in PR #2439:
URL: https://github.com/apache/helix/pull/2439#discussion_r1165929939


##########
zookeeper-api/src/main/java/org/apache/helix/zookeeper/zkclient/util/ZkPathRecursiveWatcherTrie.java:
##########
@@ -0,0 +1,271 @@
+package org.apache.helix.zookeeper.zkclient.util;
+
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.HashSet;
+import java.util.Map;
+import java.util.Objects;
+import java.util.Set;
+import java.util.concurrent.locks.Lock;
+import java.util.concurrent.locks.ReadWriteLock;
+import java.util.concurrent.locks.ReentrantReadWriteLock;
+import java.util.stream.Stream;
+
+import com.google.common.annotations.VisibleForTesting;
+import org.apache.helix.zookeeper.zkclient.RecursivePersistListener;
+
+
+/**
+ * ZkPathRecursiveWatcherTrie will be used for a registry for ZK persist recursive watcher.
+ * When persist recursive watcher is registered on path /X, ZK will send out data change for any
+ * data/child changing under the tree structure of /X. The event only include the path of changed
+ * ZNode.
+ * In ZkClient, when ever we get a dataChange event for path /X/Y/Z, we need to track back the path
+ * and notify all registered recursive persist listener and notify them about the node change.
+ * ref: https://zookeeper.apache.org/doc/r3.7.1/zookeeperProgrammers.html#sc_WatchPersistentRecursive
+ */
+public class ZkPathRecursiveWatcherTrie {
+
+  /** Root node of PathTrie */
+  private final TrieNode rootNode;
+
+  private final ReadWriteLock lock = new ReentrantReadWriteLock(true);
+
+  private final Lock readLock = lock.readLock();

Review Comment:
   can you please explain the locking model you have in mind?
   
   are you saying that a user who wants to read the Trie, will need lock? details will be very useful. I 



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