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From "sankalp kohli (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (CASSANDRA-6758) Measure data consistency in the cluster
Date Tue, 25 Feb 2014 01:27:19 GMT

    [ https://issues.apache.org/jira/browse/CASSANDRA-6758?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13911092#comment-13911092
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sankalp kohli commented on CASSANDRA-6758:
------------------------------------------

Yes if there is a mismatch of an inner node in the tree, it will log that. 
May be we can sum the ranges which do not match in Differencer in 1.2. 

Regarding performance problems with lot of streaming. I think we should pause the streams
if Cassandra detects that lot of data is being transferred causing the disk to get full or
L0 to grow. I had created this JIRA
https://issues.apache.org/jira/browse/CASSANDRA-6752

This will also make things easy to operate from such problems as you don't need to do sub
range repairs. 

> Measure data consistency in the cluster
> ---------------------------------------
>
>                 Key: CASSANDRA-6758
>                 URL: https://issues.apache.org/jira/browse/CASSANDRA-6758
>             Project: Cassandra
>          Issue Type: New Feature
>            Reporter: Jimmy MÃ¥rdell
>            Priority: Minor
>
> Running multi-DC Cassandra can be a challenge as the cluster easily tends to get out-of-sync.
We have been thinking it would be nice to measure how out of sync a cluster is and expose
those metrics somehow.
> One idea would be to just run the first half of the repair process and output the result
of the differencer. If you use Random or the Murmur3 partitioner, it should be enough to calculate
the merkle tree over a small subset of the ring as the result can be extrapolated.
> This could be exposed in nodetool. Either a separate command or perhaps a dry-run flag
to repair?
> Not sure about the output format. I think it would be nice to have one value ("% consistent"?)
within a DC, and also one value for every pair of DC's perhaps?



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