[jira] [Updated] (SPARK-5142) Possibly data may be ruined in Spark Streaming's WAL mechanism.

["Saisai Shao (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/SPARK-5142?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Saisai Shao updated SPARK-5142:
-------------------------------
    Issue Type: Sub-task  (was: Bug)
        Parent: SPARK-5238

> Possibly data may be ruined in Spark Streaming's WAL mechanism.
> ---------------------------------------------------------------
>
>                 Key: SPARK-5142
>                 URL: https://issues.apache.org/jira/browse/SPARK-5142
>             Project: Spark
>          Issue Type: Sub-task
>          Components: Streaming
>    Affects Versions: 1.2.0
>            Reporter: Saisai Shao
>
> Currently in Spark Streaming's WAL manager, data will be written into HDFS with multiple tries when meeting failure, because of lacking of transactional guarantee, previously partial-written data is not rolled back and the retried data will be appended to the last, this will ruin the file and make the WriteAheadLogReader to read data with failure.
> Firstly I think this problem is hard to fix because HDFS do not support truncate operation(HDFS-3107) or random write with specific offset.
> Secondly, I think if we meet such write exception, it is better not to try again, try again will ruin the file and make read abnormal.
> Sorry if I misunderstand anything.



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