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https://issues.apache.org/jira/browse/DRILL-6063?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Sorabh Hamirwasia updated DRILL-6063:
-------------------------------------
Reviewer: Parth Chandra
> Set correct ThreadContext ClassLoader before using Hadoop Configuration class
> in DrillClient
> --------------------------------------------------------------------------------------------
>
> Key: DRILL-6063
> URL: https://issues.apache.org/jira/browse/DRILL-6063
> Project: Apache Drill
> Issue Type: Improvement
> Components: Client - Java
> Affects Versions: 1.11.0
> Reporter: Sorabh Hamirwasia
> Assignee: Sorabh Hamirwasia
> Fix For: 1.13.0
>
>
> Drill Client uses Hadoop Configuration class in security mechanism factories.
> Configuration class internally uses ThreadContext class loader to get the
> default resources for configurations. When Drill JDBC driver is used with 3rd
> party tool like Squirrel then it creates a class loader with all Drill Driver
> related dependencies. This class loader is used to instantiate an object of
> Driver class in a separate thread. But the thread context class loader has
> dependencies related to Squirrel only. As a result of this when Hadoop
> Configuration class tries to load the resources with default values it
> doesn't find them in class path.
> If we specify hadoop dependencies in Squirrel's classpath instead of Driver
> dependencies class path then it will work since Thread Context class loader
> will have Hadoop libraries loaded too and will find the resources. But this
> is not good as it is tying up one Squirrel instance with one version of
> Hadoop which might not be true in all the cases like here when same Squirrel
> instance can be used to load multiple versions of Drill Driver having
> different hadoop version dependencies.
> To deal with this issue a simple fix is to set the Thread Context class
> loader to be same as Drill Driver dependencies class loader before accessing
> Hadoop Configuration class in Drill Client and later restore it back.
> Some pointers in code:
> * Place where JDBC driver is loaded as part of separate thread in Squirrel:
> [OpenConnectionCommand.java|https://sourceforge.net/p/squirrel-sql/git/ci/master/tree/sql12/core/src/net/sourceforge/squirrel_sql/client/mainframe/action/OpenConnectionCommand.java#l167]
> * Place where JDBC driver class is instantiated in Squirrel using Driver
> dependencies class loader:
> [SQLDriverManager.java|https://sourceforge.net/p/squirrel-sql/git/ci/master/tree/sql12/core/src/net/sourceforge/squirrel_sql/fw/sql/SQLDriverManager.java#l74]
> * Place where Hadoop Configuration class looks into Thread Context Class
> Loader:
> [Configuration.java|https://github.com/apache/hadoop-common/blob/trunk/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/conf/Configuration.java#L615]
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