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Posted to issues@tez.apache.org by "Ashutosh Chauhan (Jira)" <ji...@apache.org> on 2020/05/26 05:06:00 UTC
[jira] [Commented] (TEZ-4069) Avoid repeated computation of
preferred locations in split grouping.
[ https://issues.apache.org/jira/browse/TEZ-4069?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17116430#comment-17116430 ]
Ashutosh Chauhan commented on TEZ-4069:
---------------------------------------
+1
> Avoid repeated computation of preferred locations in split grouping.
> --------------------------------------------------------------------
>
> Key: TEZ-4069
> URL: https://issues.apache.org/jira/browse/TEZ-4069
> Project: Apache Tez
> Issue Type: Improvement
> Affects Versions: 0.9.2
> Reporter: Oliver Draese
> Priority: Major
> Attachments: TEZ-4069.1.patch, TEZ-4069.patch
>
>
> The TezSplitGrouper iterates through the list of splits multiple times, when trying to group the splits (see getGroupedSplits). Each time, it asks the locationProvider to return the array of preferred locations for the splits. This has two side effects:
> * generating the list of preferred locations can cause some CPU overhead (i.e. calculating the consistent hash in HostAffinitySplitLocationProvider), which can be avoided
> * if the list of preferred location is changing between the different loops of getGroupedSplits, we might encounter a NullPointerException. This happens if a new location appears, that was not part of the initial set of locations when populating the distinctLocations map.
> The getGroupedSplits should query the preferred locations only once (for each split) via the location provider and then memorize these instead of asking the location provider repeatedly.
>
>
>
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