[VSJoin-Exec] Mechanism III gap closure: predictable skew control plane

[ZeroJustMe]

Theme

Mechanism III: Predictable Control Plane for Skew

Problem to close

Writeup may overstate optimality while implementation is heuristic and periodic; need explicit code-faithful contract.

Implementation Tasks

• Verify/complete RCU-style AssignmentTable publication semantics:
  • lock-free reads
  • batched writes
  • atomic publish
• Finalize LoadMonitor sampled signals (cumulative + smoothed).
• Finalize rebalance controls:
  • trigger thresholds
  • per-round migration cap
  • cooldown/period
• Keep foreground path free of synchronous full-state migration.

Validation

• Test atomic remap visibility (no partial publish exposure).
• Skew workload tests: before/after imbalance indicators.
• Stress rebalance churn bounds under frequent skew changes.

Paper Follow-up (Ch3/Ch4/Ch5)

• Ch3: claim predictability, not global-optimal balancing.
• Ch4: publish semantics + heuristic trigger + migration cap.
• Ch5: skew mitigation proposition and boundary statement.

Acceptance Criteria

• Control-plane claims are strictly bounded to implemented heuristics.