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From "Daniel Meyer (JIRA)" <j...@apache.org>
Subject [jira] [Created] (CASSANDRA-6229) transfers never occur after enabling a shuffle
Date Tue, 22 Oct 2013 15:27:43 GMT
Daniel Meyer created CASSANDRA-6229:
---------------------------------------

             Summary: transfers never occur after enabling a shuffle
                 Key: CASSANDRA-6229
                 URL: https://issues.apache.org/jira/browse/CASSANDRA-6229
             Project: Cassandra
          Issue Type: Bug
          Components: Tools
            Reporter: Daniel Meyer


Using the following documentation as reference:
http://www.datastax.com/documentation/cassandra/2.0/webhelp/cassandra/tools/toolsCassandraShuffle.html

After running the 'shuffle en' step, the command does not block giving the indication that
a transfer has occurred.  However, running 'shuffle ls' at an arbitrary time after enabling
the shuffle results in a large list of pending transfers.  From the users perspective it is
unclear what is happening; however, it looks like the transfer does not actually occur.

repro steps:
1) cd to latest cassandra-2.0 branch
2) ccm create shuffle_test
3  ccm populate -n 3
4) delete the 'num_tokens' line from each cassandra.yaml file for all three nodes.
5) ccm start
6) run 'ccm node1 ring' and verify the vnodes are not enabled.
7) ccm node1 stress -o insert
8) for each node set 'num_tokens: 256' in the cassandra.yaml
9) restart the nodes
10) run 'ccm node1 ring' to verify vnodes is enabled
11) ccm node1 shuffle create
12) ccm node1 shuffle en
13) wait arbitrary amount of time and run 'ccm node1 shuffle ls'.
Expected: transfers should eventually happen and not be observed with 'shuffle ls'
Actual: transfers never seem to occur.  If in fact they do occur it is not obvious.

If transfers do in fact occur it is very difficult to tell.  This was initially discovered
on a real cluster and the cluster sat overnight without any transfers happening.  As a user
I would also expect 'shuffle en' to block.  The non blocking behavior does not seem ideal
from a user perspective.



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