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https://issues.apache.org/jira/browse/CASSANDRA-15260?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16959267#comment-16959267
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venky commented on CASSANDRA-15260:
-----------------------------------
Thanks [~mck]
> Add `allocate_tokens_for_dc_rf` yaml option for token allocation
> ----------------------------------------------------------------
>
> Key: CASSANDRA-15260
> URL: https://issues.apache.org/jira/browse/CASSANDRA-15260
> Project: Cassandra
> Issue Type: Improvement
> Components: Local/Config
> Reporter: Michael Semb Wever
> Assignee: Michael Semb Wever
> Priority: Normal
> Fix For: 4.0-alpha
>
>
> Similar to DSE's option: {{allocate_tokens_for_local_replication_factor}}
> Currently the
> [ReplicationAwareTokenAllocator|https://www.datastax.com/dev/blog/token-allocation-algorithm]
> requires a defined keyspace and a replica factor specified in the current
> datacenter.
> This is problematic in a number of ways. The real keyspace can not be used
> when adding new datacenters as, in practice, all its nodes need to be up and
> running before it has the capacity to replicate data into it. New datacenters
> (or lift-and-shifting a cluster via datacenter migration) therefore has to be
> done using a dummy keyspace that duplicates the replication strategy+factor
> of the real keyspace. This gets even more difficult come version 4.0, as the
> replica factor can not even be defined in new datacenters before those
> datacenters are up and running.
> These issues are removed by avoiding the keyspace definition and lookup, and
> presuming the replica strategy is by datacenter, ie NTS. This can be done
> with the use of an {{allocate_tokens_for_dc_rf}} option.
> It may also be of value considering whether {{allocate_tokens_for_dc_rf=3}}
> becomes the default? as this is the replication factor for the vast majority
> of datacenters in production. I suspect this would be a good improvement over
> the existing randomly generated tokens algorithm.
> Initial patch is available in
> [https://github.com/thelastpickle/cassandra/commit/fc4865b0399570e58f11215565ba17dc4a53da97]
> The patch does not remove the existing {{allocate_tokens_for_keyspace}}
> option, as that provides the codebase for handling different replication
> strategies.
>
> fyi [~blambov] [~jay.zhuang] [~chovatia.jayd...@gmail.com] [~alokamvenki]
> [~alexchueshev]
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