How to check memory in nodejs

Node.js, as a modern server-side programming language, usually handles large amounts of data and concurrent requests. Therefore, in the process of developing and operating these applications, it is crucial to detect the memory occupied by the application. This article will explain how to check the memory usage of your application in Node.js.

How to use memory in Node.js

Node.js uses two types of memory: heap memory and stack memory.

Heap memory is where dynamically allocated objects are stored in Node.js, such as arrays, objects, and strings. As programs run, they dynamically apply for space in heap memory. This means that the size of the heap memory is variable and therefore will vary in size depending on the application's operations and needs.

On the other hand, stack memory handles JavaScript function calls. Whenever a function is called, its internal variables and arguments are saved on the stack. When the function completes execution, the stack frame is popped and the memory space is released.

Node.js memory management and garbage collection

In Node.js, memory management is completed by the V8 engine. The V8 engine is a JavaScript engine developed by Google and is used to compile and execute JavaScript code.

In Node.js, V8 is responsible for managing heap memory and garbage collection. Garbage collection is an automated process that detects and clears memory space that is no longer in use. V8's garbage collector is based on a mark-sweep algorithm. As the program runs, it periodically scans the heap memory and marks those referenced objects. Afterwards, it clears those objects that are not referenced and releases the space they occupy.

Memory Check Tools in Node.js

There are many tools in Node.js that can help you check memory usage.

1. process.memoryUsage()

In Node.js, the process.memoryUsage() method can detect the memory used by the current application. This method returns an object that contains the memory usage of the process at this time. The object returned by this method has the following properties:

• rss – Resident Set Size, the sum of the physical memory currently used by the process (including the part occupied by shared libraries).
• heapTotal - the total size of the heap, represents the total memory currently applied for in the heap, including unused memory
• heapUsed - the used heap size, represents the currently applied for heap memory Used part
• external - The total number of system sockets currently used by the process

You can periodically check the heap memory usage by using the process.memoryUsage() method to understand Application memory usage and garbage collection.

The following code demonstrates how to use the process.memoryUsage() method to check memory usage:

const used = process.memoryUsage();
for (let key in used) {
 console.log(`${key} ${Math.round(used[key] / 1024 / 1024 * 100) / 100} MB`);
}

Running this code will output the memory usage of the current application on the console.

2. v8.getHeapStatistics()

The v8.getHeapStatistics() method returns an object that contains statistics on heap memory allocation, memory recycling, etc. under the V8 engine. information.

The object returned by this method contains the following properties:

• total_heap_size — The total size of the heap
• total_heap_size_executable — The size of the executable code
• total_physical_size — The total size of the heap and the sum of the sizes of shared libraries
• total_available_size — The memory size available for allocation
• used_heap_size — The size of the heap memory that has been used
• heap_size_limit — The heap size Limits
• malloced_memory — The total size of memory allocated outside the heap
• peak_malloced_memory — The largest externally allocated memory size that has ever occurred
• does_zap_garbage — A Boolean value indicating whether to perform garbage collection

The following code demonstrates how to use the v8.getHeapStatistics() method to check memory usage:

const v8 = require('v8');
const used = v8.getHeapStatistics();
for (let key in used) {
 console.log(`${key} ${Math.round(used[key] / 1024 / 1024 * 100) / 100} MB`);
}

Running this code will output heap statistics on the console.

3. heapdump

heapdump is a Node.js module that allows you to generate a snapshot of the current memory heap. This module generates a file named heapdump-YYYYMMDD_HHMMSS.heapsnapshot for further analysis of the application's memory usage.

Using the heapdump module requires installation through npm. Enter the following command in the terminal to install the heapdump module:

npm install heapdump --save

The following code demonstrates how to use the heapdump module to generate a memory snapshot:

const heapdump = require('heapdump');
heapdump.writeSnapshot((err, filename) => {
   console.log(`Heap dump written to ${filename}`);
});

The above code will generate a snapshot of the current memory heap and Save in the specified file. This file can then be analyzed using various tools to find the application's memory usage.

Summary

This article introduces the basics of memory management and garbage collection in Node.js, as well as how to use some tools to view the memory usage of your application. When we develop and maintain large applications, it is very important to understand memory usage. Using the above tools can help us discover and solve possible memory problems in time to ensure application performance and stability.

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