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Super slow SQL queries on an HC cluster

brickster_2018
Esteemed Contributor
Esteemed Contributor

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.

1 ACCEPTED SOLUTION

Accepted Solutions

brickster_2018
Esteemed Contributor
Esteemed Contributor

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.

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.

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1 REPLY 1

brickster_2018
Esteemed Contributor
Esteemed Contributor

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.

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.

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