ln-652-transaction-correctness-auditor skill

---
name: ln-652-transaction-correctness-auditor
description: "Transaction correctness audit worker (L3). Checks missing intermediate commits, transaction scope (too wide/narrow), missing rollback handling, long-held transactions, trigger/notify interaction. Returns findings with severity, location, effort, recommendations."
allowed-tools: Read, Grep, Glob, Bash
---

> **Paths:** File paths (`shared/`, `references/`, `../ln-*`) are relative to skills repo root. If not found at CWD, locate this SKILL.md directory and go up one level for repo root.

# Transaction Correctness Auditor (L3 Worker)

Specialized worker auditing database transaction patterns for correctness, scope, and trigger interaction.

## Purpose & Scope

- **Worker in ln-650 coordinator pipeline** - invoked by ln-650-persistence-performance-auditor
- Audit **transaction correctness** (Priority: HIGH)
- Check commit patterns, transaction boundaries, rollback handling, trigger/notify semantics
- Return structured findings with severity, location, effort, recommendations
- Calculate compliance score (X/10) for Transaction Correctness category

## Inputs (from Coordinator)

**MANDATORY READ:** Load `shared/references/task_delegation_pattern.md#audit-coordinator--worker-contract` for contextStore structure.

Receives `contextStore` with: `tech_stack`, `best_practices`, `db_config` (database type, ORM settings, trigger/notify patterns), `codebase_root`.

**Domain-aware:** Supports `domain_mode` + `current_domain`.

## Workflow

1) **Parse context from contextStore**
   - Extract tech_stack, best_practices, db_config
   - Determine scan_path

2) **Discover transaction infrastructure**
   - Find migration files with triggers (`pg_notify`, `CREATE TRIGGER`, `NOTIFY`)
   - Find session/transaction configuration (`expire_on_commit`, `autocommit`, isolation level)
   - Map trigger-affected tables

3) **Scan codebase for violations**
   - Trace UPDATE paths for trigger-affected tables
   - Analyze transaction boundaries (begin/commit scope)
   - Check error handling around commits

4) **Collect findings with severity, location, effort, recommendation**

5) **Calculate score using penalty algorithm**

6) **Return JSON result to coordinator**

## Audit Rules (Priority: HIGH)

### 1. Missing Intermediate Commits
**What:** UPDATE without commit when DB trigger/NOTIFY depends on transaction commit

**Detection:**
- **Step 1:** Find triggers in migrations:
  - Grep for `pg_notify|NOTIFY|CREATE TRIGGER|CREATE OR REPLACE FUNCTION.*trigger` in `alembic/versions/`, `migrations/`
  - Extract: trigger function name, table name, trigger event (INSERT/UPDATE)
- **Step 2:** Find code that UPDATEs trigger-affected tables:
  - Grep for `repo.*update|session\.execute.*update|\.progress|\.status` related to trigger tables
- **Step 3:** Check for `commit()` between sequential updates:
  - If multiple UPDATEs to trigger table occur in a loop/sequence without intermediate `commit()`, NOTIFY events are deferred until final commit
  - Real-time progress tracking breaks without intermediate commits

**Severity:**
- **CRITICAL:** Missing commit for NOTIFY/LISTEN-based real-time features (SSE, WebSocket)
- **HIGH:** Missing commit for triggers that update materialized data

**Recommendation:**
- Add `session.commit()` at progress milestones (throttled: every N%, every T seconds)
- Or move real-time notifications out of DB triggers (Redis pub/sub, in-process events)

**Effort:** S-M (add strategic commits or redesign notification path)

### 2. Transaction Scope Too Wide
**What:** Single transaction wraps unrelated operations, including slow external calls

**Detection:**
- Find `async with session.begin()` or explicit transaction blocks
- Check if block contains external calls: `await httpx.`, `await aiohttp.`, `await requests.`, `await grpc.`
- Check if block contains file I/O: `open(`, `.read(`, `.write(`
- Pattern: DB write + external API call + another DB write in same transaction

**Severity:**
- **HIGH:** External HTTP/gRPC call inside transaction (holds DB connection during network latency)
- **MEDIUM:** File I/O inside transaction

**Recommendation:** Split into separate transactions; use Saga/Outbox pattern for cross-service consistency

**Effort:** M-L (restructure transaction boundaries)

### 3. Transaction Scope Too Narrow
**What:** Logically atomic operations split across multiple commits

**Detection:**
- Multiple `session.commit()` calls for operations that should be atomic
- Pattern: create parent entity, commit, create child entities, commit (should be single transaction)
- Pattern: update status + create audit log in separate commits

**Severity:**
- **HIGH:** Parent-child creation in separate commits (orphan risk on failure)
- **MEDIUM:** Related updates in separate commits (inconsistent state on failure)

**Recommendation:** Wrap related operations in single transaction using `async with session.begin()` or unit-of-work pattern

**Effort:** M (restructure commit boundaries)

### 4. Missing Rollback Handling
**What:** `session.commit()` without proper error handling and rollback

**Detection:**
- Find `session.commit()` not inside `try/except` block or context manager
- Find `session.commit()` in `try` without `session.rollback()` in `except`
- Pattern: bare `await session.commit()` in service methods
- Exception: `async with session.begin()` auto-rollbacks (safe)

**Severity:**
- **MEDIUM:** Missing rollback (session left in broken state on failure)
- **LOW:** Missing explicit rollback when using context manager (auto-handled)

**Recommendation:** Use `async with session.begin()` (auto-rollback), or add explicit `try/except/rollback` pattern

**Effort:** S (wrap in context manager or add error handling)

### 5. Long-Held Transaction
**What:** Transaction open during slow/blocking operations

**Detection:**
- Measure scope: count lines between transaction start and commit
- Flag if >50 lines of code between `begin()` and `commit()`
- Flag if transaction contains `await` calls to external services (network latency)
- Flag if transaction contains `time.sleep()` or `asyncio.sleep()`

**Severity:**
- **HIGH:** Transaction held during external API call (connection pool exhaustion risk)
- **MEDIUM:** Transaction spans >50 lines (complex logic, high chance of lock contention)

**Recommendation:** Minimize transaction scope; prepare data before opening transaction, commit immediately after DB operations

**Effort:** M (restructure code to minimize transaction window)

## Scoring Algorithm

**MANDATORY READ:** Load `shared/references/audit_scoring.md` for unified scoring formula.

## Output Format

Return JSON to coordinator:

```json
{
  "category": "Transaction Correctness",
  "score": 5,
  "total_issues": 6,
  "critical": 1,
  "high": 2,
  "medium": 2,
  "low": 1,
  "findings": [
    {
      "severity": "CRITICAL",
      "location": "app/infrastructure/messaging/job_processor.py:412",
      "issue": "Missing intermediate commits: progress UPDATEs trigger pg_notify but no commit() between updates; real-time SSE events deferred",
      "principle": "Transaction Correctness / Trigger Semantics",
      "recommendation": "Add session.commit() at progress milestones (throttled every 5%)",
      "effort": "S"
    }
  ]
}
```

## Critical Rules

- **Do not auto-fix:** Report only
- **Trigger discovery first:** Always scan migrations for triggers/NOTIFY before analyzing transaction patterns
- **ORM-aware:** Check if ORM context manager auto-rollbacks (`async with session.begin()` is safe)
- **Exclude test transactions:** Do not flag test fixtures with manual commit/rollback
- **Database-specific:** PostgreSQL NOTIFY semantics differ from MySQL event scheduler

## Definition of Done

- contextStore parsed (tech_stack, db_config, trigger patterns)
- scan_path determined
- Trigger/NOTIFY infrastructure discovered from migrations
- All 5 checks completed:
  - missing intermediate commits, scope too wide, scope too narrow, missing rollback, long-held
- Findings collected with severity, location, effort, recommendation
- Score calculated
- JSON returned to coordinator

## Reference Files

- **Audit scoring formula:** `shared/references/audit_scoring.md`
- **Audit output schema:** `shared/references/audit_output_schema.md`

---
**Version:** 1.0.0
**Last Updated:** 2026-02-04