[KYLIN-3773] Using Mysql instead of Hive as Data Source fails with LinkageError

• Type: Bug
• Status: Closed
• Priority: Critical
• Resolution: Fixed
• Affects Version/s: v2.6.0
• Fix Version/s: v2.6.1
• Component/s: RDBMS Source
• Assignee: youcheng.zhang
• Reporter: Hubert STEFANI
• Created: 16/Jan/19 09:56
• Updated: 08/Mar/19 01:19
• Resolved: 04/Mar/19 10:29

Description

we are currently trying to test the KYLIN-3552 feature to rely directly on Mysql for data source instead of Hive.
 
(we tried as much as possible to add correct info in kylin.properties, add mysql jdbc drivers, create mysql.xml in ./conf/datasources ... as mentioned in https://github.com/apache/kylin/pull/327/files )

 
 
 
the error we entountered is ( excerpt from kylin.log ) :
 
 
2019-01-14 09:48:16,223 WARN  [http-bio-7070-exec-2] extensible.JdbcSource:50 : DataSource cannot be connected. This may not be required in a MapReduce job.
java.lang.LinkageError: loader constraint violation: loader (instance of sun/misc/Launcher$AppClassLoader) previously initiated loading for a different type with name "org/apache/kylin/common/KylinConfig"
        at java.lang.ClassLoader.defineClass1(Native Method)
        at java.lang.ClassLoader.defineClass(ClassLoader.java:763)
        at java.security.SecureClassLoader.defineClass(SecureClassLoader.java:142)
        at java.net.URLClassLoader.defineClass(URLClassLoader.java:467)
        at java.net.URLClassLoader.access$100(URLClassLoader.java:73)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:368)
        at java.net.URLClassLoader$1.run(URLClassLoader.java:362)
        at java.security.AccessController.doPrivileged(Native Method)
        at java.net.URLClassLoader.findClass(URLClassLoader.java:361)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
        at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:349)
        at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
        at org.apache.kylin.sdk.datasource.framework.SourceConnectorFactory.getJdbcConnector(SourceConnectorFactory.java:27)

with further trace :
2019-01-14 09:48:16,229 ERROR [http-bio-7070-exec-2] controller.TableController:197 :
java.lang.NullPointerException
        at org.apache.kylin.source.jdbc.extensible.JdbcExplorer.listDatabases(JdbcExplorer.java:58)
        at org.apache.kylin.rest.service.TableService.getSourceDbNames(TableService.java:280)
        at org.apache.kylin.rest.controller.TableController.showHiveDatabases(TableController.java:195)
 
 
the properties we use in kylin.properties are :
 

1. NOVAGEN – CUSTOM CONFIGURATION FOR MYSQL AS SOURCE
   kylin.source.jdbc.connection-url=jdbc:mysql://ip-172-31-36-94.eu-west-1.compute.internal:3306/decat
   kylin.source.jdbc.driver=com.mysql.jdbc.Driver
   kylin.source.jdbc.dialect=mysql
   kylin.source.jdbc.user=root
   kylin.source.jdbc.pass=
   kylin.query.pushdown.runner-class-name=org.apache.kylin.query.pushdown.PushdownRunnerSDKImpl
   kylin.source.default=16
   kylin.source.jdbc.sqoop-home=/usr/bin
   kylin.source.jdbc.adaptor=org.apache.kylin.sdk.datasource.adaptor.MysqlAdaptor
    

Issue Links

• links to: GitHub Pull Request #434