spark-issues mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Imran Rashid (JIRA)" <>
Subject [jira] [Commented] (SPARK-25855) Don't use Erasure Coding for event log files
Date Mon, 29 Oct 2018 16:12:12 GMT


Imran Rashid commented on SPARK-25855:

related to SPARK-25871 for the streaming write ahead log.

> Don't use Erasure Coding for event log files
> --------------------------------------------
>                 Key: SPARK-25855
>                 URL:
>             Project: Spark
>          Issue Type: Improvement
>          Components: Spark Core
>    Affects Versions: 2.4.0
>            Reporter: Imran Rashid
>            Priority: Major
> While testing spark with hdfs erasure coding (new in hadoop 3), we ran into a bug with
the event logs.  The main issue was a bug in hdfs (HDFS-14027), but it did make us wonder
whether Spark should be using EC for event log files in general.  Its a poor choice because
EC currently implements {{hflush()}} or {{hsync()}} as no-ops, which mean you won't see anything
in your event logs until the app is complete.  That isn't necessarily a bug, but isn't really
great.  So I think we should ensure EC is always off for event logs.
> IIUC there is *not* a problem with applications which die without properly closing the
outputstream.  It'll take a while for the NN to realize the client is gone and finish the
block, but the data should get there eventually.
> Also related are SPARK-24787 & SPARK-19531.
> The space savings from EC would be nice as the event logs can get somewhat large, but
I think other factors outweigh this.

This message was sent by Atlassian JIRA

To unsubscribe, e-mail:
For additional commands, e-mail:

View raw message