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From "Pengcheng Xiong (JIRA)" <>
Subject [jira] [Commented] (HIVE-15965) Metastore incorrectly re-uses a broken database connection
Date Sat, 25 Mar 2017 22:39:42 GMT


Pengcheng Xiong commented on HIVE-15965:

Hello, I am deferring this to Hive 3.0 as we are going to cut the first RC and it is not marked
as blocker. Please feel free to commit to the branch if this can be resolved before the release.

> Metastore incorrectly re-uses a broken database connection
> ----------------------------------------------------------
>                 Key: HIVE-15965
>                 URL:
>             Project: Hive
>          Issue Type: Bug
>          Components: Metastore
>    Affects Versions: 2.1.1
>            Reporter: Mass Dosage
>         Attachments: hive.log
> *Background*
> In our setup we have a shared standalone MetaStore server running on EMR that is accessed
by various clients (Hive CLI, HiveServer2, Spark etc.) and connects to an external MariaDB
database for the MetaStore DB. It came to our attention that MetaStore (or rather the underlying
DataNucleus / BoneCP combo) will keep re-using the same DB connections even when those get
suddenly closed for a reason that renders them unusable.
> For instance, due to a bug in the MariaDB JDBC driver v1.3.6 (see,
a huge query including over 8 thousand parameter placeholders (e.g. partition IDs in case
of a {{get_partitions_by_expr}} function call)
> will yield a {{java.nio.BufferOverflowException}} and cause the SQL connection be closed
by the driver itself.
> This will ultimately result in the abortion of all further MetaStore Thrift calls due
to the failure of {{bonecp.ConnectionHandle.prepareStatement()}}.
> Such scenarios will be then caught by DataNucleus and translated to an appropriate {{JDOException}},
only to be "ignored" by the MetaStore.{{RetryingHMSHandler}} will, of course, continue retrying
the failing operation, but this is already pointless by that time since they will invariably
fail as long as the SQL connection remains closed. Please see the attached MetaStore log [^hive.log]
for details
> (captured from Hive 2.1.1 running on Windows in Eclipse IDE).
>  *Proposed behavior*
> We suggest that MetaStore should automatically renew the DB connection whenever:
> * The connection gets closed by one of the underlying frameworks (DataNucleus, BoneCP,
JDBC driver); or
> * Query timeout is detected.
> This feature should be optional and configurable (disabled by default for backward compatibility).
Reconnection failures could probably be treated as fatal errors and cause the immediate termination
of MetaStore.

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