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Posted to issues@tez.apache.org by "Bikas Saha (JIRA)" <ji...@apache.org> on 2014/08/16 21:31:18 UTC
[jira] [Resolved] (TEZ-1400) Reducers stuck when enabling
auto-reduce parallelism (MRR case)
[ https://issues.apache.org/jira/browse/TEZ-1400?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Bikas Saha resolved TEZ-1400.
-----------------------------
Resolution: Fixed
Fix Version/s: 0.5.0
Hadoop Flags: Incompatible change,Reviewed
Looks like this is resolved via
commit 4714376e1f098d65cf6d011884ceff7870b85f64
Author: Rajesh Balamohan <rb...@apache.org>
Date: Sat Aug 16 07:01:18 2014 +0530
TEZ-1400. Reducers stuck when enabling auto-reduce parallelism
> Reducers stuck when enabling auto-reduce parallelism (MRR case)
> ---------------------------------------------------------------
>
> Key: TEZ-1400
> URL: https://issues.apache.org/jira/browse/TEZ-1400
> Project: Apache Tez
> Issue Type: Bug
> Affects Versions: 0.5.0
> Reporter: Rajesh Balamohan
> Assignee: Rajesh Balamohan
> Labels: performance
> Fix For: 0.5.0
>
> Attachments: TEZ-1400.1.patch, TEZ-1400.2.patch, TEZ-1400.3.patch, dag.dot
>
>
> In M -> R1 -> R2 case, if R1 is optimized by auto-parallelism R2 gets stuck waiting for events.
> e.g
> Map 1: 0/1 Map 2: -/- Map 5: 0/1 Map 6: 0/1 Map 7: 0/1 Reducer 3: 0/23 Reducer 4: 0/1
> ...
> ...
> Map 1: 1/1 Map 2: 148(+13)/161 Map 5: 1/1 Map 6: 1/1 Map 7: 1/1 Reducer 3: 0(+3)/3 Reducer 4: 0(+1)/1 <== Auto reduce parallelism kicks in
> ..
> Map 1: 1/1 Map 2: 161/161 Map 5: 1/1 Map 6: 1/1 Map 7: 1/1 Reducer 3: 3/3 Reducer 4: 0(+1)/1
> Job is stuck waiting for events in Reducer 4.
> [fetcher [Reducer_3] #23] org.apache.tez.runtime.library.common.shuffle.impl.ShuffleScheduler: copy(3 of 23 at 0.02 MB/s) <=== *Waiting for 20 more partitions, even though Reducer3 has been optimized to use 3 reducers
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