[GitHub] [curator] Ryan0751 commented on a diff in pull request #396: CURATOR-609 - ModeledCache attempts to deserialize empty ZNodes on deletion, resulting in exceptions

["Ryan0751 (via GitHub)" <gi...@apache.org>]

Ryan0751 commented on code in PR #396:
URL: https://github.com/apache/curator/pull/396#discussion_r1160764759


##########
curator-x-async/src/main/java/org/apache/curator/x/async/modeled/details/ModeledCacheImpl.java:
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@@ -188,9 +188,18 @@ private void internalChildEvent(TreeCacheEvent event)
         {
             ZPath path = ZPath.parse(event.getData().getPath());
             Entry<T> entry = entries.remove(path);
-            T model = (entry != null) ? entry.model : serializer.deserialize(event.getData().getData());
-            Stat stat = (entry != null) ? entry.stat : event.getData().getStat();
-            accept(ModeledCacheListener.Type.NODE_REMOVED, path, stat, model);
+            T model = null;
+            if (entry != null) {
+                model = entry.model;
+            }
+            else if (event.getData().getData() != null) {
+                model = serializer.deserialize(event.getData().getData());
+            }
+            if (model != null) {
+                Stat stat = (entry != null) ? entry.stat : event.getData().getStat();
+                accept(ModeledCacheListener.Type.NODE_REMOVED, path, stat, model);

Review Comment:
   I might help to mention the use case.
   
   Imagine that we have a model called Widget.
   
   In our application we group Widgets under sub-groups, and we can have many Widgets (100k+).  
   
   As such, we structured ZooKeeper as follows:
   /widget/<sub-group A>/<widget 1>
   /widget/<sub-group B>/<widget 2>
   
   We want to use ModeledFramework to deserialize widgets, however if we encounter a sub-group ZNode that is part of the ZNode, we'd like to just ignore that rather than cause serialization exceptions.
   
   I will have a look at ModelSerializer.raw and where it fits in here.
   
   



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