https://community.databricks.com/t5/data-engineering/super-slow-sql-queries-on-an-hc-cluster/m-p/19257#M12893 <P>I have a high concurrency cluster where multiple users are running. However, I see the queries are running very slow. I did debug the logs and see more time is spent on the Spark driver. on the Spark UI, I do not see slowness.</P> Fri, 25 Jun 2021 17:37:03 GMT brickster_2018 2021-06-25T17:37:03Z https://community.databricks.com/t5/data-engineering/super-slow-sql-queries-on-an-hc-cluster/m-p/19257#M12893 <P>I have a high concurrency cluster where multiple users are running. However, I see the queries are running very slow. I did debug the logs and see more time is spent on the Spark driver. on the Spark UI, I do not see slowness.</P> Fri, 25 Jun 2021 17:37:03 GMT https://community.databricks.com/t5/data-engineering/super-slow-sql-queries-on-an-hc-cluster/m-p/19257#M12893 brickster_2018 2021-06-25T17:37:03Z https://community.databricks.com/t5/data-engineering/super-slow-sql-queries-on-an-hc-cluster/m-p/19258#M12894 <P>It's possible the connectivity to hive metastore is causing the delay here. When there is a high degree of concurrency and contention for metastore access. Interactive clusters in DBR are configured to use up to 5 (spark.databricks.hive.metastore.client.pool.size) hive clients. So if there are more than 5 concurrently running queries that are accessing the hive for a longer time, then there could be slowness. </P><P></P><P>The easy solution to try is to increase "spark.databricks.hive.metastore.client.pool.size" . Try increasing to 32 and see if there is an improvement. </P><P></P> Fri, 25 Jun 2021 17:40:29 GMT https://community.databricks.com/t5/data-engineering/super-slow-sql-queries-on-an-hc-cluster/m-p/19258#M12894 brickster_2018 2021-06-25T17:40:29Z