AgileFlow

Memory Analysis

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Memory performance analyzer for memory leaks, event listener cleanup, subscription management, closure captures, growing collections, and large object retention

Memory Analysis

The Performance Analyzer: Memory Analysis agent is a specialized performance analyzer focused on memory leaks and excessive memory usage. It finds code patterns where memory is not properly released, grows unboundedly, or is retained unnecessarily.

When to Use

Use this agent when:

  • You need to identify event listener leaks
  • You want to check for timer and subscription cleanup
  • You're analyzing code for unbounded growing collections
  • You need to find closure captures retaining large objects
  • You're looking for excessive object retention patterns

How It Works

  1. Reads target code - Focuses on component lifecycles, event handlers, timer setup/teardown, global caches, long-lived services
  2. Identifies patterns - Looks for missing cleanup in useEffect, missing removeEventListener, uncleaned subscriptions, growing collections without bounds, closure captures, large object retention
  3. Reports findings - Generates structured findings with specific locations, severity levels, memory growth rates, and remediation steps
  4. Provides context - Shows exact code and quantifies memory impact over time

Focus Areas

  • Event listener leaks: addEventListener without corresponding removeEventListener, especially in component lifecycles
  • Timer leaks: setInterval/setTimeout not cleared on cleanup/unmount
  • Subscription leaks: Observable/EventEmitter subscriptions without unsubscribe in cleanup
  • Growing collections: Arrays, Maps, Sets that grow without bounds (caches without eviction, accumulating logs)
  • Closure captures: Closures retaining references to large objects that should be garbage collected
  • Large object retention: Storing entire response objects when only a subset is needed, global caches without size limits

Tools Available

This agent has access to: Read, Glob, Grep

Example Analysis

Given this code:

useEffect(() => {
  window.addEventListener('resize', handleResize);
  // Missing cleanup function
}, []);

The Memory Analysis analyzer would identify:

Finding: Event listener not removed in useEffect cleanup

Location: components/Header.tsx:42 Severity: HIGH Confidence: HIGH

Issue: The resize listener is added on mount but never removed on unmount. Each time the component mounts, a new listener is added without removing the old one, causing a memory leak that grows with component re-mounts.

Impact Estimate:

  • Growth rate: "1 listener per mount, ~1KB per listener"
  • Time to impact: "OOM after ~1000 mounts (significant on long-running SPA)"
  • Affected scope: "Per-component instance, multiple instances compound"

Suggested Fix:

useEffect(() => {
  window.addEventListener('resize', handleResize);
  return () => window.removeEventListener('resize', handleResize);
}, []);

Best Practices

  • Always return cleanup function from useEffect with side effects
  • Verify addEventListener has matching removeEventListener
  • Use useEffect return to clean up timers, subscriptions, event listeners
  • For global caches, implement eviction (LRU, TTL, max size)
  • Avoid storing large objects in closures unnecessarily
  • Use weak references (WeakMap, WeakSet) for caches when possible
  • Monitor memory in production with tools like New Relic, DataDog
  • Profile with Chrome DevTools Memory tab for long-running applications
  • Test component mount/unmount cycles to verify cleanup

Output Format

For each potential issue, the agent provides:

  • Location: Exact file path and line number
  • Severity: CRITICAL (causes OOM or crash), HIGH (measurable growth), MEDIUM (inefficiency), or LOW (minor retention)
  • Confidence: HIGH, MEDIUM, or LOW
  • Category: Event Listener Leak, Timer Leak, Subscription Leak, Growing Collection, Closure Capture, or Object Retention
  • Code: Relevant code snippet
  • Issue: Clear explanation of memory impact
  • Impact Estimate: Growth rate, time to impact, affected scope
  • Remediation: Specific fix with code example

Example Usage

Task(
  description: "Analyze memory leaks in UI components",
  prompt: "Review components/ for event listener leaks, timer cleanup, and growing collections. Focus on components that mount/unmount frequently.",
  subagent_type: "agileflow-perf-analyzer-memory"
)

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