How to Increase Node.js Application Performance by Avoiding Memory Leak

Everything was going well while I was working on a Node.js project, but a performance problem sprang up a few days after we released a key feature. We initially attempted to investigate the code and API optimization, however, the problem still exists. We eventually discovered that memory usage blasts up to around 90% and makes the application lag at even the most menial things. We read a variety of publications and blogs to learn more about memory leaks, so I’ll summarize all the ways we could experience them and how to prevent them.

What are memory leaks?

A memory leak is a type of programming error that occurs when a program fails to release memory that is no longer needed, causing the program to use more and more memory over time. This can eventually lead to a program crashing or becoming unresponsive. Memory leaks can be difficult to diagnose and fix, as they may not become apparent until a program has been running for a long time.

Garbage Collection in JavaScript

JavaScript is a dynamically-typed language, which means that memory allocation and deallocation is performed automatically by the JavaScript engine using a process called “garbage collection”. Garbage collection is the process of automatically detecting and freeing up memory that is no longer being used by the program.

When a JavaScript program creates objects or variables, the JavaScript engine allocates memory to store these objects or variables. The garbage collector periodically scans the program’s memory and identifies objects and variables that are no longer being used by the program. It then frees up the memory occupied by these objects and variables so that it can be reused for new objects or variables.

Javascript still has memory leaks, therefore in the segment that follows, we explain why this happens and how to stop it.

Here are some steps you can take to avoid memory leaks and increase your Node.js application performance:

1. Monitoring memory usage is important to identify memory leaks

Use tools like Node.js built-in “heapdump” module, “pm2” to monitor the memory usage of your application. These tools can help identify if there is a memory leak in your application.

One of the many use cases for which I’ve integrated PM2 into my programme is CPU utilization monitoring. You can see that I just utilized one process, which was running on a pid. Here, the CPU usage is at 63%. If the CPU usage is high for an extended length of time or while no task is being performed, we can presume that there may be memory leaks.

2. Avoid Global Variables

Avoid using global variables as they remain in the memory until the application is terminated. Instead, use local variables inside functions and modules. Instead of using var, consider using let and const to reduce memory usage and eliminate global variable pollution.

3. Use Event Emitters

Use Node.js event emitters for event-based communication between modules. This approach uses less memory compared to callbacks.  When event listeners are no longer required, make careful to remove them.

4. Avoid Synchronous Methods

Synchronous methods block the event loop, and if a large number of requests come at the same time, it can lead to poor performance and memory leaks. Use asynchronous methods and callbacks to avoid blocking the event loop.

5. Use Streams

Streams can be used for reading and writing data in chunks rather than loading the entire file into memory. This approach reduces the memory footprint of your application.

6. Close Database Connections

Close database connections after you’re done with them to free up memory. This applies to other resources like network connections and file descriptors.

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About the Author

Akshay Malta is a javascript enthusiast, experienced in React, Node, and Angular, working as a Software developer in West Agile Labs. He loves solving complex problems whether it is programming or designing a system