[jira] [Issue Comment Edited] (CASSANDRA-2388) ColumnFamilyRecordReader fails for a given split because a host is down, even if records could reasonably be read from other replica.

["Mck SembWever (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CASSANDRA-2388?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13094658#comment-13094658 ] 

Mck SembWever edited comment on CASSANDRA-2388 at 9/1/11 6:39 AM:
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see last comment. (say if this should be a separate bug...)

Maybe hadoop's task allocation isn't working properly because i've an unbalanced ring (i'm working in parallel to fix that).
If this is the case i think it's an unfortunate limitation (the ring must be balanced to get any decent hadoop performance).
It's also probably likely when using {{ConfigHelper.setInputRange(..)}} that the number of nodes involved is small (approaching RF).
With the default hadoop scheduler your hadoop cluster is occupied while just a few taskTrackers are busy. Of course switching to FairScheduler will help some here.

I'll take a look into hadoop's task allocation code as well...

      was (Author: michaelsembwever):
    see last comment. (say if this should be a separate bug...)
  
> ColumnFamilyRecordReader fails for a given split because a host is down, even if records could reasonably be read from other replica.
> -------------------------------------------------------------------------------------------------------------------------------------
>
>                 Key: CASSANDRA-2388
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-2388
>             Project: Cassandra
>          Issue Type: Bug
>          Components: Hadoop
>    Affects Versions: 0.6
>            Reporter: Eldon Stegall
>            Assignee: Mck SembWever
>              Labels: hadoop, inputformat
>             Fix For: 0.7.9, 0.8.5
>
>         Attachments: 0002_On_TException_try_next_split.patch, CASSANDRA-2388-addition1.patch, CASSANDRA-2388-extended.patch, CASSANDRA-2388.patch, CASSANDRA-2388.patch, CASSANDRA-2388.patch, CASSANDRA-2388.patch
>
>
> ColumnFamilyRecordReader only tries the first location for a given split. We should try multiple locations for a given split.

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