hadoop-mapreduce-issues mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From "Chris Douglas (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (MAPREDUCE-4882) Error in estimating the length of the output file in Spill Phase
Date Fri, 08 May 2015 21:44:01 GMT

     [ https://issues.apache.org/jira/browse/MAPREDUCE-4882?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Chris Douglas updated MAPREDUCE-4882:
-------------------------------------
          Resolution: Duplicate
       Fix Version/s: 2.6.0
    Target Version/s:   (was: )
              Status: Resolved  (was: Patch Available)

Fixed in MAPREDUCE-6063. Sorry Jerry; didn't see this.

> Error in estimating the length of the output file in Spill Phase
> ----------------------------------------------------------------
>
>                 Key: MAPREDUCE-4882
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-4882
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>    Affects Versions: 0.20.2, 1.0.3
>         Environment: Any Environment
>            Reporter: Lijie Xu
>            Assignee: Jerry Chen
>              Labels: BB2015-05-TBR, patch
>             Fix For: 2.6.0
>
>         Attachments: MAPREDUCE-4882.patch
>
>   Original Estimate: 1h
>  Remaining Estimate: 1h
>
> The sortAndSpill() method in MapTask.java has an error in estimating the length of the
output file. 
> The "long size" should be "(bufvoid - bufstart) + bufend" not "(bufvoid - bufend) + bufstart"
when "bufend < bufstart".
> Here is the original code in MapTask.java.
>  private void sortAndSpill() throws IOException, ClassNotFoundException,
>                                        InterruptedException {
>       //approximate the length of the output file to be the length of the
>       //buffer + header lengths for the partitions
>       long size = (bufend >= bufstart
>           ? bufend - bufstart
>           : (bufvoid - bufend) + bufstart) +
>                   partitions * APPROX_HEADER_LENGTH;
>       FSDataOutputStream out = null;
> ------------------------------------------------------------------------------
> I had a test on "TeraSort". A snippet from mapper's log is as follows:
> MapTask: Spilling map output: record full = true
> MapTask: bufstart = 157286200; bufend = 10485460; bufvoid = 199229440
> MapTask: kvstart = 262142; kvend = 131069; length = 655360
> MapTask: Finished spill 3
> In this occasioin, Spill Bytes should be (199229440 - 157286200) + 10485460 = 52428700
(52 MB) because the number of spilled records is 524287 and each record costs 100B.



--
This message was sent by Atlassian JIRA
(v6.3.4#6332)

Mime
View raw message