[GitHub] [accumulo] jzgithub1 commented on a change in pull request #1443: Fixes #1220 - Removes ZooKeeper watches on table configs when table is deleted.

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jzgithub1 commented on a change in pull request #1443: Fixes #1220  -  Removes ZooKeeper watches on table configs when table is deleted.
URL: https://github.com/apache/accumulo/pull/1443#discussion_r353378733
 
 

 ##########
 File path: core/src/main/java/org/apache/accumulo/fate/zookeeper/ZooCache.java
 ##########
 @@ -435,6 +475,46 @@ public T retry() {
     return zr.retry();
   }
 
+  /*
+   * Some of the table configuration parameters are possibly not in ZooKeeper yet and even though
+   * you are able you should not put a watcher on them to observe the NodeCreated event. If you do
+   * that and the ZNode for that configuration is never created, you will have no way to delete the
+   * watcher you created for it in Zookeeper. Unremovable watchers that are created for for table
+   * configs that never actually have a Znode is causing memory leaks in Accumulo instances that
+   * create and delete tables at a high rate.
+   */
+
+  private boolean isWatched(ZooKeeper zooKeeper, String zPath)
+      throws KeeperException, InterruptedException {
+
+    boolean watched = true;
+
+    if (znodeExists.contains(zPath))
+      return watched;
+
+    Matcher configMatcher = TABLE_SETTING_CONFIG_PATTERN.matcher(zPath);
+
+    if (configMatcher.matches()) {
+      Stat stat;
+      try {
+        stat = zooKeeper.exists(zPath, false);
+      } catch (KeeperException.BadVersionException | KeeperException.NoNodeException e1) {
+        throw new ConcurrentModificationException();
 
 Review comment:
   Thanks.  I will just re-throw the exception.  

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