Xuefu Zhang created HIVE-7593:
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Summary: Instantiate SparkClient per user session
Key: HIVE-7593
URL: https://issues.apache.org/jira/browse/HIVE-7593
Project: Hive
Issue Type: Sub-task
Components: Spark
Reporter: Xuefu Zhang
SparkContext is the main class via which Hive talk to Spark cluster.
SparkClient encapsulates a SparkContext instance. Currently all user sessions
share a single SparkClient instance in HiveServer2. While this is good enough
for a POC, even for our first two milestones, this is not desirable for a
multi-tenancy environment and gives least flexibility to Hive users. Here is
what we propose:
1. Have a SparkClient instance per user session. The SparkClient instance is
created when user executes its first query in the session. It will get
destroyed when user session ends.
2. The SparkClient is instantiated based on the spark configurations that are
available to the user, including those defined at the global level and those
overwritten by the user (thru set command, for instance).
3. Ideally, when user changes any spark configuration during the session, the
old SparkClient instance should be destroyed and a new one based on the new
configurations is created. This may turn out to be a little hard, and thus it's
a "nice-to-have". If not implemented, we need to document that subsequent
configuration changes will not take effect in the current session.
Please note that there is a thread-safety issue on Spark side where multiple
SparkContext instances cannot coexist in the same JVM (SPARK-2243). We need to
work with Spark community to get this addressed.
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