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Posted to issues@spark.apache.org by "Saisai Shao (JIRA)" <ji...@apache.org> on 2015/01/08 11:04:35 UTC
[jira] [Commented] (SPARK-5142) Possibly data may be ruined in
Spark Streaming's WAL mechanism.
[ https://issues.apache.org/jira/browse/SPARK-5142?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14269117#comment-14269117 ]
Saisai Shao commented on SPARK-5142:
------------------------------------
cc\ [~tdas], what is your opinion? Thanks a lot.
> 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: Bug
> 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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