[jira] [Commented] (SPARK-21475) Change the usage of FileInputStream/OutputStream to Files.newInput/OutputStream in the critical path

["Apache Spark (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/SPARK-21475?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16310619#comment-16310619 ] 

Apache Spark commented on SPARK-21475:
--------------------------------------

User 'jerryshao' has created a pull request for this issue:
https://github.com/apache/spark/pull/20144

> Change the usage of FileInputStream/OutputStream to Files.newInput/OutputStream in the critical path
> ----------------------------------------------------------------------------------------------------
>
>                 Key: SPARK-21475
>                 URL: https://issues.apache.org/jira/browse/SPARK-21475
>             Project: Spark
>          Issue Type: Improvement
>          Components: Shuffle, Spark Core
>    Affects Versions: 2.3.0
>            Reporter: Saisai Shao
>            Assignee: Saisai Shao
>            Priority: Minor
>
> Java's {{FileInputStream}} and {{FileOutputStream}} overrides {{finalize()}}, even this file input/output stream is closed correctly and promptly, it will still leave some memory footprints which will get cleaned in Full GC. This will introduce two side effects:
> 1. Lots of memory footprints regarding to Finalizer will be kept in memory and this will increase the memory overhead. In our use case of external shuffle service, a busy shuffle service will have bunch of this object and potentially lead to OOM.
> 2. The Finalizer will only be called in Full GC, and this will increase the overhead of Full GC and lead to long GC pause.
> So to fix this potential issue, here propose to use NIO's Files#newInput/OutputStream instead in some critical paths like shuffle.
> https://www.cloudbees.com/blog/fileinputstream-fileoutputstream-considered-harmful



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