ln-628-concurrency-auditor

name	ln-628-concurrency-auditor
description	Concurrency audit worker (L3). Checks race conditions, missing async/await, resource contention, thread safety, deadlock potential. 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.

Concurrency Auditor (L3 Worker)

Specialized worker auditing concurrency and async patterns.

Purpose & Scope

• Worker in ln-620 coordinator pipeline
• Audit concurrency (Category 11: High Priority)
• Check race conditions, async/await, thread safety
• Calculate compliance score (X/10)

Inputs (from Coordinator)

Receives contextStore with tech stack, language, codebase root, output_dir.

Workflow

1. Parse context + output_dir
2. Check concurrency patterns
3. Collect findings
4. Calculate score
5. Write Report: Build full markdown report in memory per shared/templates/audit_worker_report_template.md, write to {output_dir}/628-concurrency.md in single Write call
6. Return Summary: Return minimal summary to coordinator

Audit Rules

1. Race Conditions

What: Shared state modified without synchronization

Detection Patterns:

Language	Pattern	Grep
Python	Global modified in async	global\s+\w+ inside async def
TypeScript	Module-level let in async	^let\s+\w+ at file scope + async function modifies it
Go	Map access without mutex	map\[.*\].*= without sync.Mutex in same file
All	Shared cache	cache\[.*\]\s*= or cache\.set without lock

Severity:

• CRITICAL: Race in payment/auth (payment, balance, auth, token in variable name)
• HIGH: Race in user-facing feature
• MEDIUM: Race in background job

Recommendation: Use locks, atomic operations, message queues

Effort: M-L

2. Missing Async/Await

What: Callback hell or unhandled promises

Detection Patterns:

Issue	Grep	Example
Callback hell	\.then\(.*\.then\(.*\.then\(	.then().then().then()
Fire-and-forget	async.*\(\) not preceded by await	saveToDb() without await
Missing await	return\s+new\s+Promise in async function	Should just return await or return value
Dangling promise	\.catch\(\s*\)	Empty catch swallows errors

Severity:

• HIGH: Fire-and-forget async (can cause data loss)
• MEDIUM: Callback hell (hard to maintain)
• LOW: Mixed Promise styles

Recommendation: Convert to async/await, always await or handle promises

Effort: M

3. Resource Contention

What: Multiple processes competing for same resource

Detection Patterns:

Issue	Grep	Example
File lock missing	open\(.*["']w["']\) without flock or lockfile	Concurrent file writes
Connection exhaustion	create_engine\(.*pool_size check if pool_size < 5	DB pool too small
Concurrent writes	writeFile or fs\.write without lock check	File corruption risk

Severity:

• HIGH: File corruption risk, DB exhaustion
• MEDIUM: Performance degradation

Recommendation: Use connection pooling, file locking, asyncio.Lock

Effort: M

4. Thread Safety Violations

What: Shared mutable state without synchronization

Detection Patterns:

Language	Safe Pattern	Unsafe Pattern
Go	sync.Mutex with map	map[...] without Mutex in same struct
Rust	Arc<Mutex<T>>	Rc<RefCell<T>> in multi-threaded context
Java	synchronized or ConcurrentHashMap	HashMap shared between threads
Python	threading.Lock	Global dict modified in threads

Grep patterns:

• Go unsafe: type.*struct\s*{[^}]*map\[ without sync.Mutex in same struct
• Python unsafe: global\s+\w+ in function + threading.Thread in same file

Severity: HIGH (data corruption possible)

Recommendation: Use thread-safe primitives

Effort: M

5. Deadlock Potential

What: Lock acquisition in inconsistent order

Detection Patterns:

Issue	Grep	Example
Nested locks	with\s+\w+_lock:.*with\s+\w+_lock: (multiline)	Lock A then Lock B
Lock in loop	for.*:.*\.acquire\(\)	Lock acquired repeatedly without release
Lock + external call	.acquire\(\) followed by await or requests.	Holding lock during I/O

Severity: HIGH (deadlock freezes application)

Recommendation: Consistent lock ordering, timeout locks (asyncio.wait_for)

Effort: L

6. Blocking I/O in Event Loop (Python asyncio)

What: Synchronous blocking calls inside async functions

Detection Patterns:

Blocking Call	Grep in async def	Replacement
time.sleep	time\.sleep inside async def	await asyncio.sleep
requests.	requests\.(get|post) inside async def	httpx or aiohttp
open() file	open\( inside async def	aiofiles.open

Severity:

• HIGH: Blocks entire event loop
• MEDIUM: Minor blocking (<100ms)

Recommendation: Use async alternatives

Effort: S-M

Scoring Algorithm

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

Output Format

MANDATORY READ: Load shared/templates/audit_worker_report_template.md for file format.

Write report to {output_dir}/628-concurrency.md with category: "Concurrency" and checks: race_conditions, missing_await, resource_contention, thread_safety, deadlock_potential, blocking_io.

Return summary to coordinator:

Report written: docs/project/.audit/ln-620/{YYYY-MM-DD}/628-concurrency.md
Score: X.X/10 | Issues: N (C:N H:N M:N L:N)

Reference Files

• Worker report template: shared/templates/audit_worker_report_template.md
• Audit scoring formula: shared/references/audit_scoring.md
• Audit output schema: shared/references/audit_output_schema.md

Critical Rules

• Do not auto-fix: Report only, concurrency fixes require careful human review
• Language-aware detection: Use language-specific patterns (Go sync.Mutex, Python asyncio.Lock, Java synchronized)
• Effort realism: S = <1h, M = 1-4h, L = >4h
• Critical path escalation: Race conditions in payment/auth = CRITICAL, regardless of other factors
• Exclusions: Skip test files, skip single-threaded CLI tools, skip generated code

Definition of Done

• contextStore parsed (language, concurrency model, output_dir)
• All 6 checks completed (race conditions, missing await, resource contention, thread safety, deadlock potential, blocking I/O)
• Findings collected with severity, location, effort, recommendation
• Score calculated per shared/references/audit_scoring.md
• Report written to {output_dir}/628-concurrency.md (atomic single Write call)
• Summary returned to coordinator

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Version: 3.0.0 Last Updated: 2025-12-23