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From "Jonathan Ellis (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-2388) ColumnFamilyRecordReader fails for a given split because a host is down, even if records could reasonably be read from other replica.
Date Thu, 30 Jun 2011 00:33:28 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-2388?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13057568#comment-13057568
] 

Jonathan Ellis commented on CASSANDRA-2388:
-------------------------------------------

bq. this means a dead c* node will bring down a TT

Again: _this is what you want to happen_.  As long as the C* process on the same node is down,
you want the TT to be blacklisted and the jobs to go elsewhere.

bq. In a hadoop cluster with 3 nodes this means for 24hrs you're lost 33% throughput

Right, but the real cause is because the C* process is dead, not b/c the TT is blacklisted.
 Making the TT read from other nodes will only hurt your network, not fix the throughput problem,
b/c i/o is the bottleneck.

> 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: 0.7.6, 0.8.0
>            Reporter: Eldon Stegall
>            Assignee: Jeremy Hanna
>              Labels: hadoop, inputformat
>             Fix For: 0.7.7, 0.8.2
>
>         Attachments: 0002_On_TException_try_next_split.patch, CASSANDRA-2388-addition1.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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