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https://issues.apache.org/jira/browse/HIVE-27884?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17787357#comment-17787357
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László Bodor commented on HIVE-27884:
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cc: [~prasanth_j]: if you can recall any obvious problems related to this
> LLAP: Reuse FileSystem objects from cache across different tasks in the same
> LLAP daemon
> ----------------------------------------------------------------------------------------
>
> Key: HIVE-27884
> URL: https://issues.apache.org/jira/browse/HIVE-27884
> Project: Hive
> Issue Type: Improvement
> Reporter: László Bodor
> Priority: Major
>
> Originally, when the task runner was added to HIVE-10028
> ([here|https://github.com/apache/hive/blob/23f40bd88043db3cb4efe3a763cbfd5c01a81d2f/llap-server/src/java/org/apache/hadoop/hive/llap/daemon/impl/TaskRunnerCallable.java#L202]),
> the FileSystem.closeAllForUGI was commented out for some reasons, and then,
> in the scope of HIVE-9898 it was simply added back,
> [here|https://github.com/apache/hive/commit/91c46a44dd9fbb68d01f22e93c4ce0931a4598e0#diff-270dbe6639879ca543ae21c44a239af6145390726d45fee832be809894bfc88eR236]
> A FileSystem.close call basically does the
> [following|https://github.com/apache/hadoop/blob/0c10bab7bb77aa4ea3ca26c899ab28131561e052/hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/FileSystem.java#L2700-L2710]:
> 1. delete all paths that were marked as delete-on-exit.
> 2. removes the instance from the cache
> I saw that we
> [call|https://github.com/apache/hive/blob/eb6f0b0c57dd55335927b7dde08cd47f4d00e74d/llap-server/src/java/org/apache/hadoop/hive/llap/daemon/impl/TaskRunnerCallable.java#L302]
>
> {code}
> FileSystem.closeAllForUGI
> {code}
> at the end of all task attempts, so we almost completely disable hadoop's
> filesystem cache during a long-running LLAP daemon lifecycle
> some investigations on azure showed that creating a filesystem can be quite
> expensive, as it involves the recreation of a whole object hierarchy like:
> {code}
> AzureBlobFileSystem -> AzureBlobFileSystemStore --> AbfsClient ->
> TokenProvider(MsiTokenProvider)
> {code}
> which ends up pinging the token auth endpoint of azure, leading to e.g. a
> HTTP response 429
> We need to check whether we can remove this closeAllForUGI in LLAP.
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