[jira] [Created] (CASSANDRA-6758) Measure data consistency in the cluster

["Jimmy Mårdell (JIRA)" <ji...@apache.org>]

Jimmy Mårdell created CASSANDRA-6758:
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             Summary: 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 Mårdell
            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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