Truyền Luồng (Stream) Tải Tệp Lớn Trong Node.js Tránh Lỗi Tràn Bộ Nhớ RAM

Serving large files directly from Node.js without a CDN or object storage proxy requires streaming. Loading a 1GB file into memory with fs.readFileSync consumes 1GB of server RAM per connected user—rapidly leading to process termination.

Streaming Files with Node.js HTTP Streams

Node.js readable streams buffer only small chunks (typically 64KB) in memory at any given moment:

TypeScript

import http from 'http';
import fs from 'fs';
import path from 'path';

const server = http.createServer((req, res) => {
  const filePath = path.join(process.cwd(), 'files', 'large-dataset.pdf');

  fs.stat(filePath, (err, stats) => {
    if (err) {
      res.writeHead(404, { 'Content-Type': 'text/plain' });
      return res.end('File not found');
    }

    // Set binary response headers
    res.writeHead(200, {
      'Content-Type': 'application/pdf',
      'Content-Length': stats.size,
      'Content-Disposition': 'attachment; filename="large-dataset.pdf"',
      'Accept-Ranges': 'bytes',
    });

    const readStream = fs.createReadStream(filePath);

    // Automatically handles TCP backpressure
    readStream.pipe(res);

    // Handle client disconnects
    req.on('close', () => {
      readStream.destroy();
    });
  });
});

server.listen(3000, () => console.log('Download server running on port 3000'));

Verified Test Asset.pdf

Download our 500MB PDF sample file to test stream backpressure handling in your server code.

Tải File Mẫu 500MB PDF →

Understanding Stream Backpressure

When a server can read from disk faster than a client can receive data over the network, stream.pipe(res) automatically pauses the read stream until the client's socket drain buffer clears, preserving server memory.

Câu Hỏi Thường Gặp (FAQ)

Why does Node.js run out of memory when serving large files?▾

Using fs.readFileSync() or res.send(buffer) loads the entire file into heap memory. For a 1GB file with 10 concurrent downloads, that is 10GB of RAM. Use fs.createReadStream().pipe(res) instead — it reads in 64KB chunks, keeping memory constant regardless of file size.

What is backpressure in Node.js streams?▾

Backpressure occurs when the writable stream (HTTP response) cannot consume data as fast as the readable stream (file read) produces it. Using .pipe() handles backpressure automatically by pausing the file read when the response write buffer is full.

How do I add HTTP Range request support to my Node.js file server?▾

Parse the Range header, calculate the byte range, use fs.createReadStream(path, { start, end }), and respond with 206 Partial Content and the Content-Range header. This enables browser resume support and video seeking.

Truyền Luồng (Stream) Tải Tệp Lớn Trong Node.js Tránh Lỗi Tràn Bộ Nhớ RAM

Streaming Files with Node.js HTTP Streams

Understanding Stream Backpressure

Nguyễn Đại Long

Bài viết này có hữu ích không?

Thảo Luận Kỹ Thuật & Đóng Góp Ý Kiến (0)

Câu Hỏi Thường Gặp (FAQ)

Bài Viết Liên Quan