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https://issues.apache.org/jira/browse/CASSANDRA-13441?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15972044#comment-15972044
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Jeff Jirsa commented on CASSANDRA-13441:
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Aleksey mentioned he had some concerns with the approach in IRC and, more
importantly, suggested a cleaner way to do it (rather than change the hashing,
write new system tables with fixed time stamps). I've pulled the branch for now
because it's going to change (significantly)
> Schema version changes for each upgraded node in a rolling upgrade, causing
> migration storms
> --------------------------------------------------------------------------------------------
>
> Key: CASSANDRA-13441
> URL: https://issues.apache.org/jira/browse/CASSANDRA-13441
> Project: Cassandra
> Issue Type: Bug
> Components: Schema
> Reporter: Jeff Jirsa
> Assignee: Jeff Jirsa
> Fix For: 4.x
>
>
> In versions < 3.0, during a rolling upgrade (say 2.0 -> 2.1), the first node
> to upgrade to 2.1 would add the new tables, setting the new 2.1 version ID,
> and subsequently upgraded hosts would settle on that version.
> When a 3.0 node upgrades and writes its own new-in-3.0 system tables, it'll
> write the same tables that exist in the schema with brand new timestamps. As
> written, this will cause all nodes in the cluster to change schema (to the
> version with the newest timestamp). On a sufficiently large cluster with a
> non-trivial schema, this could cause (literally) millions of migration tasks
> to needlessly bounce across the cluster.
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