[GitHub] [curator] kezhuw commented on a diff in pull request #478: CURATOR-688. SharedCount will be never updated successful when version of ZNode is overflow.

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

kezhuw commented on code in PR #478:
URL: https://github.com/apache/curator/pull/478#discussion_r1313839760


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curator-recipes/src/main/java/org/apache/curator/framework/recipes/shared/SharedValue.java:
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@@ -196,8 +196,12 @@ public boolean trySetValue(VersionedValue<byte[]> previous, byte[] newValue) thr
     private void updateValue(int version, byte[] bytes) {
         while (true) {
             VersionedValue<byte[]> current = currentValue.get();
-            if (current.getVersion() >= version) {
-                // A newer version was concurrently set.

Review Comment:
   I am not sure wether `SharedValue` was designed to work with multiple owners, but I saw there is a background watcher to update value and also there is no rule to forbid concurrent usages. So, I assume it should work well in case of concurrency.
   
   Then, let me assume a situation:
   1. `current.getVersion` is `Integer.MAX_VALUE`.
   2. Thread1 call `trySetValue` and succeed to get overflowed version `Integer.MIN_VALUE`, but the call to `updateValue` is somewhat delayed.
   3. Thread2 (assume watcher, which runs in ZooKeeper thread if I am not wrong) call `updateVersion` with version `Integer.MIN_VALUE + 1`. According to the code, this will be ignored.
   4. Thread1 call `updateValue` to continue its task with version `Integer.MIN_VALUE`. It succeeds.
   5. That is all, assume no changes anymore. I know it may not realistic.
   
   `current` stores dated version while the javadoc says "All clients watching the same path will have the up-to-date value (considering ZK's normal consistency guarantees)".



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