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Posted to common-issues@hadoop.apache.org by "Walter Su (JIRA)" <ji...@apache.org> on 2015/11/02 03:36:27 UTC

[jira] [Updated] (HADOOP-12047) Indicate preference not to affect input buffers during coding in erasure coder

     [ https://issues.apache.org/jira/browse/HADOOP-12047?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Walter Su updated HADOOP-12047:
-------------------------------
          Resolution: Fixed
        Hadoop Flags: Reviewed
       Fix Version/s:     (was: HDFS-7285)
                      3.0.0
    Target Version/s: 3.0.0
              Status: Resolved  (was: Patch Available)

Committed to trunk. Thanks [~drankye] for contribution.

> Indicate preference not to affect input buffers during coding in erasure coder
> ------------------------------------------------------------------------------
>
>                 Key: HADOOP-12047
>                 URL: https://issues.apache.org/jira/browse/HADOOP-12047
>             Project: Hadoop Common
>          Issue Type: Sub-task
>            Reporter: Kai Zheng
>            Assignee: Kai Zheng
>             Fix For: 3.0.0
>
>         Attachments: HADOOP-12047-HDFS-7285-v1.patch, HADOOP-12047-v2.patch, HADOOP-12047-v3.patch, HADOOP-12047-v4.patch, HADOOP-12047-v5.patch, initial-poc.patch
>
>
> It's good to define and ensure input buffers are not affected during coding process in raw erasure coders. Below are copied from discussion with [~jingzhao] in HDFS-8481:
> bq. In that case we cannot reuse the source buffers I guess? Then do we need to expose this information in the decoder?
> bq. Good catch Jing! Yes in this case we can't reuse the source buffers here as they need to be passed to caller/applications without being changed. I'm planning to re-implement the Java coders in HADOOP-12041 and related, when done it's possible to ensure the input buffers not to be affected. Benefits of doing this in coder layer: 1) a more clear contract between coder and caller in more general sense for the inputs; 2) concrete coder may have specific tweak to optimize in the aspect, ideally no input data copying at all, worst, make the copy, but all transparent to callers; 3) allow new coders (LRC, HH) to be layered on other primitive coders (RS, XOR) more easily.



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