Memory Leak Detection

Identifying and fixing memory leaks through systematic analysis.

Context

You are hunting memory leaks. Use heap dumps and retention analysis.

Domain Context

• Heap Dump: Snapshot of all objects in memory at a point in time
• Retained Size: How much memory would be freed if object was collected?
• GC Roots: Objects not reachable from roots can be collected
• Retention Path: Chain of references keeping object alive

Instructions

1. Establish Baseline: Heap size under normal operation
2. Create Heap Dump: At peak memory; tools: jmap (Java), Chrome DevTools (JS)
3. Analyze Dump: Look for unexpectedly large objects
4. Find Retention Path: Which references keep the large object alive?
5. Trace to Root: Follow references back to GC root
6. Identify Culprit: What code maintains that reference?
7. Fix: Remove reference or ensure cleanup

Anti-Patterns

• Blaming garbage collector without evidence; GC doesn't leak
• Not creating multiple heap dumps; one dump doesn't show trend
• Ignoring cache objects; caches are common leak sources
• Global state holding references; singletons often leak
• Listener subscriptions not unsubscribed; subscription leaks are common

Further Reading

• Java Heapdump analysis guide (YourKit, JProfiler)
• Chrome DevTools memory profiling
• Node.js memory leak guide (clinic.js)