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From "Vishwajeet Dusane (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HADOOP-12876) [Azure Data Lake] Support for process level FileStatus cache to optimize GetFileStatus frequent opeations
Date Thu, 03 Mar 2016 11:25:18 GMT

    [ https://issues.apache.org/jira/browse/HADOOP-12876?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15177700#comment-15177700
] 

Vishwajeet Dusane commented on HADOOP-12876:
--------------------------------------------

 * FileStatus cache is simple process level cache which mirrors backend storage FileStatus
objects.
 * Time to live on the FileStatus cached object is limited. 5 seconds default and configurable
through core-site.xml
 * FileStatus objects are stored in Synchronized LinkedHashMap. Where key is fully qualified
file path and value is FileStatus java object along with time to live information.
 * FileStatus cache is built based on successful responses to GetFileStatus and ListStatus
calls for existing files/folders. Non existent files/folder are not maintained in the cache.
 * FileStatus cache motivation is to avoid multiple GetFileStatus calls to the ADL backend
and as a result gain better performance for job startup and during execution.


> [Azure Data Lake] Support for process level FileStatus cache to optimize GetFileStatus
frequent opeations
> ---------------------------------------------------------------------------------------------------------
>
>                 Key: HADOOP-12876
>                 URL: https://issues.apache.org/jira/browse/HADOOP-12876
>             Project: Hadoop Common
>          Issue Type: New Feature
>          Components: fs, fs/azure, tools
>            Reporter: Vishwajeet Dusane
>            Assignee: Vishwajeet Dusane
>
> Add support to cache GetFileStatus and ListStatus response locally for limited period
of time. Local cache for limited period of time would optimize number of calls for GetFileStatus
operation.
> One of the example  where local limited period cache would be useful - terasort ListStatus
on input directory follows with GetFileStatus operation on each file within directory. For
2048 input files in a directory would save 2048 GetFileStatus calls during start up (Using
the ListStatus response to cache FileStatus instances).



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