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From "Alejandro Abdelnur (JIRA)" <j...@apache.org>
Subject [jira] [Updated] (MAPREDUCE-4963) StatisticsCollector improperly keeps track of "Last Day" and "Last Hour" statistics for new TaskTrackers
Date Sat, 26 Jan 2013 04:31:13 GMT

     [ https://issues.apache.org/jira/browse/MAPREDUCE-4963?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
]

Alejandro Abdelnur updated MAPREDUCE-4963:
------------------------------------------

       Resolution: Fixed
    Fix Version/s: 1.2.0
     Hadoop Flags: Reviewed
           Status: Resolved  (was: Patch Available)

Thanks Robert. Committed to branch-1.
                
> StatisticsCollector improperly keeps track of "Last Day" and "Last Hour" statistics for
new TaskTrackers
> --------------------------------------------------------------------------------------------------------
>
>                 Key: MAPREDUCE-4963
>                 URL: https://issues.apache.org/jira/browse/MAPREDUCE-4963
>             Project: Hadoop Map/Reduce
>          Issue Type: Bug
>          Components: mrv1
>    Affects Versions: 1.1.1
>            Reporter: Robert Kanter
>            Assignee: Robert Kanter
>             Fix For: 1.2.0
>
>         Attachments: MAPREDUCE-4963.patch
>
>
> The StatisticsCollector keeps track of updates to the "Total Tasks Last Day", "Succeed
Tasks Last Day", "Total Tasks Last Hour", and "Succeeded Tasks Last Hour" per Task Tracker
which is displayed on the JobTracker web UI.  It uses buckets to manage when to shift task
counts from "Last Hour" to "Last Day" and out of "Last Day".  After the JT has been running
for a while, the connected TTs will have the max number of buckets and will keep shifting
them at each update.  If a new TT connects (or an old on rejoins), it won't have the max number
of buckets, but the code that drops the buckets uses the same counter for all sets of buckets.
 This means that new TTs will prematurely drop their buckets and the stats will be incorrect.
 
> example:
> # Max buckets is 5
> # TaskTracker A has these values in its buckets [4, 2, 0, 3, 10] (i.e. 19)
> # A new TaskTracker, B, connects; it has nothing in its buckets: [ ] (i.e. 0)
> # TaskTracker B runs 3 tasks and TaskTracker A runs 5
> # An update occurs
> # TaskTracker A has [2, 0, 3, 10, 5] (i.e. 20)
> # TaskTracker B should have [3] but it will drop that bucket after adding it during the
update and instead have [ ] again (i.e. 0)
> # TaskTracker B will keep doing that forever and always show 0 in the web UI
> We can fix this by not using the same counter for all sets of buckets

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