Stream memory usage

streams-test-5.js

'use strict';

const fs = require('fs');

fs.writeFileSync('test-small.bin', Buffer.alloc(100));
fs.writeFileSync('test-large.bin', Buffer.alloc(100000));

const blockMaxSize = 4 * 1024 * 1024; // 4 MiB

const out = { buf: [], length: 0 };
let built = 0;

function tick() {
  built++;
  if (built % 1000 === 0) {
    console.log(`RSS [${built}]: ${process.memoryUsage().rss / 1024 / 1024} MiB`);
  }
  let stream;
  if (built % 2 === 0) {
    const stream = fs.createReadStream('./test-small.bin');
    stream.on('data', function (data) {
      //data = Buffer.from(data); // WARNING: uncommenting this line fixes things somehow
      out.buf.push(data)
      out.length += data.length
      if (out.length >= blockMaxSize) {
        out.buf = []
        out.length = 0
      }
    });
    stream.once('end', tick);
  } else {
    const stream = fs.createReadStream('./test-large.bin');
    stream.on('data', function() {});
    stream.once('end', tick);
    /* Alternatively:
    fs.readFileSync('./test-large.bin');
    setImmediate(tick);
    */
  }
}

tick();