1. Introduction

• Brief overview of the repository and its purpose.
• Importance of memory management in Node.js applications.

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2. Background on Memory Management

• Traditional Memory Leaks in Languages like C
  • How languages without garbage collection (like C) handle memory.
  • Common pitfalls of manual memory management and how it compares to garbage-collected languages.

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3. Understanding Memory Leaks in Node.js

• What is a Memory Leak in Node.js?

  • Definition and consequences of memory leaks in JavaScript/Node.js applications.

• How the Garbage Collector (GC) Works in Node.js

  • Explanation of Node.js’s garbage collection process.
  • Concepts of mark-and-sweep, generational garbage collection, and memory retention.

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4. Common Causes of Memory Leaks in Node.js

• Uncleared Listeners and Event Emitters

  • How event listeners, especially in server-based applications, can lead to memory leaks.

• Global Variables and Caching

  • Risks of caching too much data or keeping references to large objects in global scope.

• Closures and Function Scopes

  • Issues arising from closures and retaining variables longer than needed.

• Unoptimized Data Structures (e.g., Arrays, Maps)

  • Potential for memory leaks due to large, long-lived collections.

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5. Using WeakMap and FinalizationRegistry to Detect Garbage Collection (GC) Activity

• Introduction to WeakMap

  • Explanation of how WeakMap works in JavaScript.

• Tracking Object Collection with WeakMap

  • Using WeakMap to see if objects are garbage-collected, providing insight into potential memory leaks.

• FinalizationRegistry

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6. Forcing Garbage Collection in Node.js (Manual GC Trigger)

• How to Trigger Garbage Collection in Node.js

  • Using the --expose-gc flag and calling global.gc() for debugging purposes.

• When and Why to Use Manual GC

  • Guidelines for using manual GC for memory testing only, not in production.

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7. Using the Snip3 Hunt Method

• Introduction to Snip3 Hunt Methodology

  • Brief overview of the “three-snapshot” comparison technique.

• Taking and Comparing Snapshots

  • Step-by-step guide on capturing memory snapshots with Node.js tools (e.g., Chrome DevTools, node --inspect).
  • Analyzing and comparing snapshots to isolate memory leaks over time.

• Example Workflow for Snip3 Hunt

  • A simple example to demonstrate the method in practice.

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8. Case Study: Jest’s Memory Leak Detection Using WeakMap

• How Jest Uses FinalizationRegistry for Leak Detection

  • Explanation of how Jest leverages FinalizationRegistry to detect memory leaks in tests.

• Applying the secret Jest Approach in Your Code or Tests

  • Practical steps to integrate a similar FinalizationRegistry strategy for tracking leaks in your own testing setup.

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9. Tools and Techniques for Memory Leak Detection

• Node.js Native Tools

  • Brief on tools like Chrome DevTools, node --inspect, and node-heapdump.

• Additional Utilities

  • Mention of tools like clinic.js, memwatch-next, or any other preferred memory profiling utilities.

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10. Best Practices for Preventing Memory Leaks in Node.js

• Guidelines for Managing Event Listeners and Closures
• Efficient Use of Global Variables and Caches
• Regularly Profiling and Monitoring Memory Usage
• allways run your jest with --detectLeaks

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11. Conclusion

• Recap of key points.
• Encouragement to incorporate memory management strategies into routine development and testing.

Refs

https://jestjs.io/blog/2017/12/18/jest-22#experimental-leak-detection jestjs/jest#12973 https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/FinalizationRegistry https://v8.dev/blog/trash-talk https://v8.dev/blog/tracing-js-dom

https://nodejs.org/en/learn/diagnostics/memory/using-gc-traces

relevant

https://dev.to/codux/experiments-with-the-javascript-garbage-collector-2ae3

memory leak in nodejs

nodejs/node#53335 https://github.com/nodejs/node/blob/main/test/parallel/test-primitive-timer-leak.js#L15 https://github.com/nodejs/node/blob/main/test/common/gc.js

Research

check if global.gc call minor or mijor gc