Heap snapshot for memory leaks in Node.js - Mini Project: Build & Apply

Heap Snapshot for Memory Leaks in Node.js

📖 Scenario: You are working on a Node.js server application that sometimes uses too much memory. You want to find out if there are memory leaks by taking a heap snapshot. This helps you see what objects stay in memory longer than they should.

🎯 Goal: Build a simple Node.js script that creates a heap snapshot file to analyze memory usage and detect leaks.

📋 What You'll Learn

Create a Node.js script that imports the inspector module

Start a new inspector session

Take a heap snapshot and save it to a file named heap.heapsnapshot

Close the inspector session after the snapshot is saved

💡 Why This Matters

🌍 Real World

Heap snapshots help developers find memory leaks by showing what objects remain in memory. This is useful for improving app performance and stability.

💼 Career

Understanding how to capture and analyze heap snapshots is valuable for Node.js backend developers and performance engineers to diagnose memory issues.

1

Import the inspector module and start a session

Write code to import the inspector module and create a new inspector.Session() instance called session. Then call session.connect() to start the session.

Node.js

// Import inspector and start a session
// Your code here

Need a hint?

Use require('inspector') to import the module. Then create a session with new inspector.Session() and connect it.

2

Create a writable stream for the heap snapshot file

Add code to import the fs module and create a writable stream called writeStream that writes to a file named heap.heapsnapshot.

Node.js

const inspector = require('inspector');
const session = new inspector.Session();
session.connect();

// Import fs and create writeStream for 'heap.heapsnapshot'
// Your code here

Need a hint?

Use require('fs') to import the file system module. Then use fs.createWriteStream('heap.heapsnapshot') to create the stream.

3

Take the heap snapshot and pipe data to the file

Use session.on('HeapProfiler.addHeapSnapshotChunk') to listen for snapshot data chunks. In the callback, write each chunk to writeStream. Then call session.post('HeapProfiler.takeHeapSnapshot') to start the snapshot.

Node.js

const inspector = require('inspector');
const session = new inspector.Session();
session.connect();

const fs = require('fs');
const writeStream = fs.createWriteStream('heap.heapsnapshot');

// Listen for snapshot chunks and write to file
// Start taking heap snapshot
// Your code here

Need a hint?

Listen for 'HeapProfiler.addHeapSnapshotChunk' events and write each chunk to the file. Then call session.post('HeapProfiler.takeHeapSnapshot') to start.

4

Close the write stream and disconnect session after snapshot

Add a listener for 'HeapProfiler.reportHeapSnapshotProgress' event. When done === true, close writeStream and call session.disconnect() to end the session.

Node.js

const inspector = require('inspector');
const session = new inspector.Session();
session.connect();

const fs = require('fs');
const writeStream = fs.createWriteStream('heap.heapsnapshot');

session.on('HeapProfiler.addHeapSnapshotChunk', (m) => {
  writeStream.write(m.params.chunk);
});

session.post('HeapProfiler.takeHeapSnapshot');

// Close stream and disconnect session when snapshot is done
// Your code here

Need a hint?

Use the 'HeapProfiler.reportHeapSnapshotProgress' event to detect when the snapshot is done. Then close the file and disconnect the session.