worldmonitor/todos/184-pending-p2-pipeline-non-atomic-partial-persist.md

status, priority, issue_id, tags, dependencies

status	priority	issue_id	tags	dependencies
pending	p2	184	code-review phase-0 regional-intelligence persistence consistency redis

Upstash /pipeline is not transactional - partial failure leaves inconsistent snapshot state

Problem Statement

scripts/regional-snapshot/persist-snapshot.mjs:56-73 issues 6 commands via /pipeline (SET timestamp, SET by-id, SET latest, ZADD index, ZREMRANGEBYSCORE, DEL live). Pipeline executes sequentially but not atomically. Partial failure leaves inconsistent state (latest pointer to a snapshot not in the index, or vice versa). Phase 1 may rely on the index to enumerate accessible snapshots and trip on the inconsistency.

Findings

• /pipeline is batched but not transactional on Upstash
• 6 writes cover 3 state shapes: timestamp view, id view, latest pointer, index
• Partial failure surfaces as silent drift between pointer and index
• No repair job exists

Proposed Solutions

Option 1: Use /multi-exec for atomic persistence

Upstash supports MULTI/EXEC transactions via /multi-exec endpoint.

Pros: All-or-nothing guarantee; no inconsistent state Cons: Slightly more expensive; needs a small client change Effort: Medium Risk: Low

Option 2: Document partial-persist contract + repair job

Accept non-atomicity; write a repair job that reconciles latest/index on next run.

Pros: Keeps existing pipeline code Cons: Runtime readers still see drift until repair fires; more complex Effort: Medium Risk: Low

Recommended Action

Technical Details

File: scripts/regional-snapshot/persist-snapshot.mjs:56-73 Commands in the current pipeline:

1. SET snapshot:ts:{region}:{ts}
2. SET snapshot🆔{region}:{id}
3. SET snapshot:latest:{region}
4. ZADD snapshot:index:{region}
5. ZREMRANGEBYSCORE snapshot:index:{region}
6. DEL snapshot:live:{region}

Acceptance Criteria

• Use /multi-exec for atomic persistence OR
• Document the partial-persist contract and add a repair job

Work Log

Resources

• PR #2940
• PR #2942