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From "Hudson (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HIVE-3826) Rollbacks and retries of drops cause org.datanucleus.exceptions.NucleusObjectNotFoundException: No such database row)
Date Sat, 22 Dec 2012 14:17:12 GMT

    [ https://issues.apache.org/jira/browse/HIVE-3826?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13538819#comment-13538819
] 

Hudson commented on HIVE-3826:
------------------------------

Integrated in Hive-trunk-h0.21 #1871 (See [https://builds.apache.org/job/Hive-trunk-h0.21/1871/])
    HIVE-3826 Rollbacks and retries of drops cause 
org.datanucleus.exceptions.NucleusObjectNotFoundException: No such database row)
(Kevin Wilfong via namit) (Revision 1425247)

     Result = FAILURE
namit : http://svn.apache.org/viewcvs.cgi/?root=Apache-SVN&view=rev&rev=1425247
Files : 
* /hive/trunk/metastore/src/java/org/apache/hadoop/hive/metastore/ObjectStore.java

                
> Rollbacks and retries of drops cause org.datanucleus.exceptions.NucleusObjectNotFoundException:
No such database row)
> ---------------------------------------------------------------------------------------------------------------------
>
>                 Key: HIVE-3826
>                 URL: https://issues.apache.org/jira/browse/HIVE-3826
>             Project: Hive
>          Issue Type: Bug
>          Components: Metastore
>    Affects Versions: 0.11
>            Reporter: Kevin Wilfong
>            Assignee: Kevin Wilfong
>         Attachments: HIVE-3826.1.patch.txt
>
>
> I'm not sure if this is the only cause of the exception "org.datanucleus.exceptions.NucleusObjectNotFoundException:
No such database row)" from the metastore, but one cause seems to be related to a drop command
failing, and being retried by the client.
> Based on focusing on a single thread in the metastore with DEBUG level logging, I was
seeing the objects that were intended to be dropped remaining in the PersistenceManager cache
even after a rollback.  The steps seemed to be as follows:
> 1) First attempt to drop the table, the table is pulled into the PersistenceManager cache
for the purposes of dropping
> 2) The drop fails, e.g. due to a lock wait timeout on the SQL backend, this causes a
rollback of the transaction
> 3) The drop is retried using a different thread on the metastore Thrift server or a different
server and succeeds
> 4) Back on the original thread of the original Thrift server someone tries to perform
some write operation which produces a commit.  This causes those detached objects related
to the dropped table to attempt to reattach, causing JDO to query the SQL backend for those
objects which it can't find.  This causes the exception.
> I was able to reproduce this regularly using the following sequence of commands:
> Hive client 1 (Hive1): connected to a metastore Thrift server running a single thread,
I hard coded a RuntimeException into the code to drop a table in the ObjectStore, specifically
right before the commit in preDropStorageDescriptor, to induce a rollback.  I also turned
off all retries at all layers of the metastore.
> Hive client 2 (Hive2): connected to a separate metastore Thrift server running with standard
configs and code
> 1: On Hive1, CREATE TABLE t1 (c STRING);
> 2: On Hive1, DROP TABLE t1; // This failed due to the hard coded exception
> 3: On Hive2, DROP TABLE t1; // Succeeds
> 4: On Hive1, CREATE DATABASE d1; // This database already existed, I'm not sure why this
was necessary, but it didn't work without it, it seemed to have an affect on the order objects
were committed in the next step
> 5: On Hive1, CREATE DATABASE d2; // This database didn't exist, it would fail with the
NucleusObjectNotFoundException
> The object that would cause the exception varied, I saw the MTable, the MSerDeInfo, and
MTablePrivilege from the table that attempted to be dropped.

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