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https://issues.apache.org/jira/browse/CASSANDRA-12777?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15577330#comment-15577330
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Dikang Gu commented on CASSANDRA-12777:
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[~blambov] thanks a lot for the review! I addressed your comments and here is a
new commit:
https://github.com/DikangGu/cassandra/commit/402050e32732e67055935689951a56f92b9be281
1. wraparound calculation, for BigIntegerToken, if it's above maximum, I will
`mod` the max token. I also add test and validation for it.
2. I put the createTokenInfo in constructor because I need to populate the unit
info according to the tokens.
3. agree, removed the createTokenInfo
4. I tried different fractions, from 0.50 - 0.99, 0.50 will fail the assertion,
otherwise, they do not make much difference.
https://gist.github.com/DikangGu/acd8f568f67b11082443419a8d503b01, I put 0.75
in this commit.
5. Add the `TokenAllocatorBase`, I keep the factory class because I think it's
cleaner to keep the factory method there.
Thanks!
> Optimize the vnode allocation for single replica per DC
> -------------------------------------------------------
>
> Key: CASSANDRA-12777
> URL: https://issues.apache.org/jira/browse/CASSANDRA-12777
> Project: Cassandra
> Issue Type: Improvement
> Reporter: Dikang Gu
> Assignee: Dikang Gu
> Fix For: 3.x
>
>
> The new vnode allocation algorithm introduced in CASSANDRA-7032 is optimized
> for the situation that there are multiple replicas per DC.
> In our production environment, most cluster only has one replica, in this
> case, the algorithm does not work perfectly. It always tries to split token
> ranges by half, so that the ownership of "min" node could go as low as ~60%
> compared to avg.
> So for single replica case, I'm working on a new algorithm, which is based on
> Branimir's previous commit, to split token ranges by "some" percentage,
> instead of always by half. In this way, we can get a very small variation of
> the ownership among different nodes.
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