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https://issues.apache.org/jira/browse/TAJO-847?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14033545#comment-14033545
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ASF GitHub Bot commented on TAJO-847:
-------------------------------------
Github user cepiross commented on a diff in the pull request:
https://github.com/apache/tajo/pull/39#discussion_r13847503
--- Diff:
tajo-catalog/tajo-catalog-server/src/main/java/org/apache/tajo/catalog/store/AbstractDBStore.java
---
@@ -152,9 +152,20 @@ protected String getCatalogUri() {
return catalogUri;
}
+ protected boolean isConnValid(int timeout) throws CatalogException {
--- End diff --
As @jihoonson stated, I experienced Tajo Session removal, indicating that
MariaDB JDBC disconnection, when I tried to execute a query directly after
dropping table schema, as following:
**NOTE! this log is only after applying latest TAJO-847 patch**
2014-06-17 12:48:35,466 INFO org.apache.tajo.master.GlobalEngine:
=============================================
2014-06-17 12:48:35,489 INFO org.apache.tajo.catalog.CatalogServer:
relation "linewalks.test" is deleted from the catalog (192.168.0.15:26005)
2014-06-17 12:48:35,504 INFO org.apache.tajo.master.GlobalEngine: relation
"linewalks.test" is purged.
2014-06-17 12:48:43,526 INFO org.apache.tajo.master.GlobalEngine: Query:
select * from table20
2014-06-17 12:48:43,526 INFO org.apache.tajo.master.GlobalEngine:
hive.query.mode:false
2014-06-17 12:48:43,529 INFO org.apache.tajo.catalog.store.MariaDBStore:
Conn abortion when checking isValid; retrieve false to create another Conn.
2014-06-17 12:48:43,565 INFO org.apache.tajo.master.GlobalEngine:
=============================================
2014-06-17 12:48:43,565 INFO org.apache.tajo.master.GlobalEngine: Optimized
Query:
…
2014-06-17 12:48:43,565 INFO org.apache.tajo.master.GlobalEngine:
=============================================
2014-06-17 12:48:47,272 INFO org.apache.tajo.master.session.SessionManager:
Session a1121c5d-51ea-4397-b345-e062cd32350f is removed.
[Error description]
In other words, the query sequence always incurs NullPointerException in
invoking Conn.isValid method when using up-to-date MariaDB JDBC Connector.
[Solution]
To avoid the drawback, I have agreed with @jihoonson to insert
MariaDBStore-specific NPE handling, isConnValid method; which is a temporal
solution until MariaDB JDBC resolves disconnection issue.
> Supporting MariaDB-based Store, which is compatible with MySQL.
> ---------------------------------------------------------------
>
> Key: TAJO-847
> URL: https://issues.apache.org/jira/browse/TAJO-847
> Project: Tajo
> Issue Type: New Feature
> Components: catalog, conf and scripts
> Affects Versions: 0.8.0
> Environment: Tested with Hadoop 2.4.0, Tajo 0.8.0, MariaDB 5.5.37,
> MariaDB-Java-Client (JDBC) 1.1.7 in OpenJDK 1.7.0_55 + Ubuntu 14.04 LTS x86_64
> Reporter: Jinhang Choi
> Assignee: Jinhang Choi
> Priority: Minor
> Fix For: 0.8.0
>
> Attachments: TAJO-847.patch
>
> Original Estimate: 24h
> Remaining Estimate: 24h
>
> There exists an open-source database MariaDB (http://mariadb.org) which can
> be replacement for MySQL; Since the interface of MariaDB is perfectly
> compatible to that of MySQL, it is easy to construct CatalogStore to use
> MariaDB in Tajo.
> Therefore, I hereby suggest MariaDBStore by duplicating MySQLStore.
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