How to debug a memory leak in Node.js?

Memory leaks in Node.js can be elusive, but they are certainly not impossible to track down and fix. Here are some steps you could take to debug a memory leak in Node.js:

1. Using a Node.js Process Manager: Tools like PM2 allows you to monitor the memory usage of your application in real time.

1. Heap Snapshots: Heap snapshots allow you to see the memory usage of your application at a given point of time. The heap snapshot contains information about all objects in the JavaScript heap. These snapshots can be compared to identify what objects might be taking up memory.

1. Heapdumps: A module in the npm registry allows you to create heapdumps that can be loaded into the Chrome DevTools memory profiler for analysis. You can even create a heapdump when your application consumes too much memory or at regular intervals.

1. Chrome DevTools: Load your memory snapshots or heapdumps in Chrome DevTools. Use it for profiling memory usage and find out what references are preventing garbage collection.

1. Identifying Common Memory Leak Patterns: Some common patterns which might suggest memory leaks include
Unexpected growth in heap memory usage over time.
- A steady increase in CPU usage without a corresponding increase in load.
- Functions that take progressively longer to complete.

1. Profiling Your Application: Use tools like v8-profiler to profile your application and identify what parts of your code might be leading to memory leaks.

1. Memory Leak Libraries: Libraries such as memwatch-next and node-memwatch can help you detect potential memory leaks by listening to their leak event.

1. Garbage Collection and Memory Leak Tools: Tools like the gc-profiler can provide you with stats about the garbage collection which you could use to find memory leaks.

1. Using ‘node —inspect’: Start Node.js with —inspect flag allows to open Chrome Devtools dedicated to Node.js instance, and directly analyze performance using JavaScript CPU Profile and Memory snapshots.

1. Unit Tests: Good unit test coverage will help you spot memory leaks when you modify your code. Libraries such as jest or mocha, assisted by chai and sinon, are very effective.

Identifying the root cause of a memory leak can be a challenging task. Nonetheless, with consistent monitoring and the use of proper tools, you can ensure that your application performs smoothly for extended durations.