Mirror layered writes during async step-down

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    • Type: Task
    • Resolution: Unresolved
    • Priority: Major - P3
    • None
    • Affects Version/s: None
    • Component/s: Layered Tables
    • None
    • Storage Engines - Foundations
    • 139.39
    • Storage Execution 2026-08-31
    • None

      Summary

      During an async step-down window, leader writes to layered tables must be mirrored to both the stable and ingest constituents. Stable must be written first so WiredTiger conflict detection remains authoritative.

      Scope

      • Mirror insert, update, modify, remove, and reserve.
      • Encode values independently for each constituent.
      • Represent remove as a stable removal plus an ingest tombstone.
      • Snapshot and decode the original logical value before modify, then construct the full ingest mirror.
      • Make a failed ingest mirror transaction-fatal.
      • Preserve ingest-only routing for tables created without a stable constituent.
      • Preserve existing transaction-level straddler checks.
      • Update layered async step-down and tombstone-encoding tests.

      Non-goals

      • Do not remove the step-down mutex.
      • Do not simplify leader reads.
      • Do not support prepared transactions during the window.
      • Do not add optimized truncate mirroring.

            Assignee:
            Wei Hu
            Reporter:
            Wei Hu
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              Created:
              Updated: