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Node.js Performance

Heap Snapshots

Compare heap snapshots to find retained objects and leaks.

memory

Detailed Description

A heap snapshot captures the objects currently retained by V8. Comparing snapshots before and after traffic helps reveal which objects keep growing and are not garbage collected.

Use snapshots when memory grows over time. Common causes are unbounded caches, arrays that keep request data, listeners that are never removed, or closures holding large objects.

Mental Model

snapshot A
-> simulate traffic
-> snapshot B
-> compare retained objects

When To Use

  • ->RSS or heap grows after traffic
  • ->Garbage collection does not reclaim memory
  • ->You suspect retained request data
Tools: v8.writeHeapSnapshot, Chrome DevTools memory tab
heap-snapshot.js

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Output

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