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From "Tathagata Das (JIRA)" <>
Subject [jira] [Commented] (SPARK-3292) Shuffle Tasks run incessantly even though there's no inputs
Date Wed, 01 Oct 2014 21:18:35 GMT


Tathagata Das commented on SPARK-3292:

I mentioned this in the PR but I am adding it here as well.  Not returning an RDD can mess
up a lot of the logic and semantics. For example if there is a transform() followed by updateStateByKey(),
the result will be unpredictable. updateStateByKey expects the previous batch to have a state
RDD. If it does not find any state RDD it will assume that this the start of the streamign
computation and effectively initialize again, forgetting the previous states from 2 batches
ago. So this change is incorrect.

Regarding the original problem of creating too many empty files, you can filter that out by
doing explicitly saving yourself.

    dstream.foreachRDD { case (rdd, time) => 
        if (rdd.take(1).size == 1) {

> Shuffle Tasks run incessantly even though there's no inputs
> -----------------------------------------------------------
>                 Key: SPARK-3292
>                 URL:
>             Project: Spark
>          Issue Type: Improvement
>          Components: Streaming
>    Affects Versions: 1.0.2
>            Reporter: guowei
> such as repartition groupby join and cogroup
> for example. 
> if i want the shuffle outputs save as hadoop file ,even though  there is no inputs ,
many emtpy file generate too.
> it's too expensive , 

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