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https://issues.apache.org/jira/browse/HIVE-27884?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
 ]

László Bodor updated HIVE-27884:
--------------------------------
    Description: 
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.

> Reuse FileSystem objects from cache across different tasks in the same 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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