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https://issues.apache.org/jira/browse/CASSANDRA-8119?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15330854#comment-15330854
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Aleksey Yeschenko commented on CASSANDRA-8119:
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I've said this elsewhere, and I'll repeat it again, here: this is a niche
requirement that is not worth the complications it's brining to the table.
Additionally, you can't really encapsulate it in a UDF, as there are more
factors that are CL-dependent. The behaviour of read repair, and speculative
retry, can/should wary a lot depending on a CL used - and when it doesn't, we
see bugs like CASSANDRA-11980. It could be an interface, though, like
[~thorntsg] suggested. Keeping it this opaque is probably not ideal for the
drivers, though.
Also, while you could stick it to schema, I don't see how it's a fit,
conceptually, and not a (conceptually) dirty hack. Sorry. I really believe it
shouldn't be done, at least in this manner.
> More Expressive Consistency Levels
> ----------------------------------
>
> Key: CASSANDRA-8119
> URL: https://issues.apache.org/jira/browse/CASSANDRA-8119
> Project: Cassandra
> Issue Type: New Feature
> Components: CQL
> Reporter: Tyler Hobbs
> Fix For: 3.x
>
>
> For some multi-datacenter environments, the current set of consistency levels
> are too restrictive. For example, the following consistency requirements
> cannot be expressed:
> * LOCAL_QUORUM in two specific DCs
> * LOCAL_QUORUM in the local DC plus LOCAL_QUORUM in at least one other DC
> * LOCAL_QUORUM in the local DC plus N remote replicas in any DC
> I propose that we add a new consistency level: CUSTOM. In the v4 (or v5)
> protocol, this would be accompanied by an additional map argument. A map of
> {DC: CL} or a map of {DC: int} is sufficient to cover the first example. If
> we accept a special keys to represent "any datacenter", the second case can
> be handled. A similar technique could be used for "any other nodes".
> I'm not in love with the special keys, so if anybody has ideas for something
> more elegant, feel free to propose them. The main idea is that we want to be
> flexible enough to cover any reasonable consistency or durability
> requirements.
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