[jira] [Created] (ZOOKEEPER-1624) PrepRequestProcessor abort multi-operation incorrectly

["Thawan Kooburat (JIRA)" <ji...@apache.org>]

Thawan Kooburat created ZOOKEEPER-1624:
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             Summary: PrepRequestProcessor abort multi-operation incorrectly
                 Key: ZOOKEEPER-1624
                 URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1624
             Project: ZooKeeper
          Issue Type: Bug
          Components: server
            Reporter: Thawan Kooburat
            Priority: Critical


We found this issue when trying to issue multiple instances of the following multi-op concurrently

multi {
1. create sequential node /a- 
2. create node /b
}

The expected result is that only the first multi-op request should success and the rest of request should fail because /b is already exist

However, the reported result is that the subsequence multi-op failed because of sequential node creation failed which is not possible.

Below is the return code for each sub-op when issuing 3 instances of the above multi-op asynchronously

1. ZOK, ZOK
2. ZOK, ZNODEEXISTS,
3. ZNODEEXISTS, ZRUNTIMEINCONSISTENCY,

When I added more debug log. The cause is that PrepRequestProcessor rollback outstandingChanges of the second multi-op incorrectly causing sequential node name generation to be incorrect. Below is the sequential node name generated by PrepRequestProcessor

1. create /a-0001
2. create /a-0003
3. create /a-0001

The bug is getPendingChanges() method. In failed to copied ChangeRecord for the parent node (/).  So rollbackPendingChanges() cannot restore the right previous change record of the parent node when aborting the second multi-op

The impact of this bug is that sequential node creation on the same parent node may fail until the previous one is committed. I am not sure if there is other implication or not.  


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