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https://issues.apache.org/jira/browse/CASSANDRA-6758?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13910214#comment-13910214
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Benedict commented on CASSANDRA-6758:
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bq. I wonder if it would be possible to calculate and save an abbreviated
merkle tree when writing each sstable, that could be combined cheaply to give
this answer.
Hmm. Thinking about it for just a few seconds more, this is highly unlikely to
be workable since we would be hashing multiple versions of a partition key. It
might be workable for datasets that are append only, but not sure if it's a
worthwhile optimisation for that case alone.
> 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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