[jira] [Commented] (HDFS-16422) Fix thread safety of EC decoding during concurrent preads

["Tao Li (Jira)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HDFS-16422?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17716656#comment-17716656 ] 

Tao Li commented on HDFS-16422:
-------------------------------

Hi [~cndaimin] , have you tested the impact on performance? And have you used it in a production environment? Thanks.
 
 

> Fix thread safety of EC decoding during concurrent preads
> ---------------------------------------------------------
>
>                 Key: HDFS-16422
>                 URL: https://issues.apache.org/jira/browse/HDFS-16422
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: dfsclient, ec, erasure-coding
>    Affects Versions: 3.3.0, 3.3.1
>            Reporter: daimin
>            Assignee: daimin
>            Priority: Critical
>              Labels: pull-request-available
>             Fix For: 3.4.0, 3.2.3, 3.3.3
>
>          Time Spent: 3h 40m
>  Remaining Estimate: 0h
>
> Reading data on an erasure-coded file with missing replicas(internal block of block group) will cause online reconstruction: read dataUnits part of data and decode them into the target missing data. Each DFSStripedInputStream object has a RawErasureDecoder object, and when we doing pread concurrently, RawErasureDecoder.decode will be invoked concurrently too. RawErasureDecoder.decode is not thread safe, as a result of that we get wrong data from pread occasionally.



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