Re: Review Request 65716: HIVE-18696: The partition folders might not get cleaned up properly in the HiveMetaStore.add_partitions_core method if an exception occurs

[Marta Kuczora via Review Board <no...@reviews.apache.org>]

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https://reviews.apache.org/r/65716/
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(Updated April 5, 2018, 3:40 p.m.)


Review request for hive, Alexander Kolbasov, Peter Vary, and Adam Szita.


Changes
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Rebasing the patch


Bugs: HIVE-18696
    https://issues.apache.org/jira/browse/HIVE-18696


Repository: hive-git


Description
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The idea behind the patch is

1) Separate the partition validation from starting the tasks which create the partition folders. 
Instead of doing the checks on the partitions and submit the tasks in one loop, separated the validation into a different loop. So first iterate through the partitions, validate the table/db names, and check for duplicates. Then if all partitions were correct, in the second loop submit the tasks to create the partition folders. This way if one of the partitions is incorrect, the exception will be thrown in the first loop, before the tasks are submitted. So we can be sure that no partition folder will be created if the list contains an invalid partition.

2) Handle the exceptions which occur during the execution of the tasks differently.
Previously if an exception occured in one task, the remaining tasks were canceled, and the newly created partition folders were cleaned up in the finally part. The problem was that it could happen that some tasks were still not finished with the folder creation when cleaning up the others, so there could have been leftover folders. After doing some testing it turned out that this use case cannot be avoided completely when canceling the tasks.
The idea of this patch is to set a flag if an exception is thrown in one of the tasks. This flag is visible in the tasks and if its value is true, the partition folders won't be created. Then iterate through the remaining tasks and wait for them to finish. The tasks which are started before the flag got set will then finish creating the partition folders. The tasks which are started after the flag got set, won't create the partition folders, to avoid unnecessary work. This way it is sure that all tasks are finished, when entering the finally part where the partition folders are cleaned up.


Diffs (updated)
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  standalone-metastore/src/main/java/org/apache/hadoop/hive/metastore/HiveMetaStore.java 8539fea 
  standalone-metastore/src/test/java/org/apache/hadoop/hive/metastore/client/TestAddPartitions.java 8555eee 
  standalone-metastore/src/test/java/org/apache/hadoop/hive/metastore/client/TestAddPartitionsFromPartSpec.java b32954f 


Diff: https://reviews.apache.org/r/65716/diff/6/

Changes: https://reviews.apache.org/r/65716/diff/5-6/


Testing
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Added some new tests cases to the TestAddPartitions and TestAddPartitionsFromPartSpec tests.


Thanks,

Marta Kuczora