[CASSANDRA-15454] Update generations and update comments for altered distributed system keyspaces

• Type: Bug
• Status: Resolved
• Priority: Normal
• Resolution: Fixed
• Fix Version/s: 4.0-alpha3, 4.0
• Component/s: Cluster/Schema
• Bug Category: Degradation
• Severity: Low
• Complexity: Low Hanging Fruit
• Discovered By: Code Inspection
• Platform: All
• Since Version: 4.0-alpha

Source Control Link

8202845facd741f01fbfbbec93d6a3c8e6078644

Test and Documentation Plan

N/A

• Assignee: Aleksey Yeschenko
• Reporter: Aleksey Yeschenko

Authors

Aleksey Yeschenko

Reviewers

Sam Tunnicliffe

• Created: 16/Dec/19 11:07
• Updated: 21/Dec/20 08:07
• Resolved: 16/Dec/19 17:35

Description

In 4.0, we set memtable_flush_period_in_ms to 0 (from 1 hour previously), and changed default chunk length from 64KiB to 16KiB. On startup we would try to override existing schema definitions for system_traces, system_distributed, and system_auth to reflect these changes, but because these are changes to smaller values, while timestamps remain the same, these will never override existing, pre-upgrade values from 3.0 or 3.11. As a result, a schema migration request will be pushed by a node on every bounce to every replica, causing unnecessary and ultimately fruitless work.

Bumping the generations fixes the issue, and documenting the changes doesn't hurt either.

Issue Links

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