Using shared-structs with workers <3

README.md

Using shared-structs with Workers <3

This showcases how you can use shared-structs over an SharedArrayBuffer, to share complex data structures between worker_threads in Node.js

The main.js example starts a worker and passes a shared struct to it.

The worker will periodically update the struct with an incrementing tick and a random number

After 2s it will read the source code of itself into the worker as well.

main.js

const { Worker } = require('worker_threads')
const { shared } = require('./structs')

const struct = shared(Buffer.from(new SharedArrayBuffer(shared.bytes)))

const worker = new Worker('./worker.js')
worker.postMessage(struct.rawBuffer.buffer)

setInterval(function () {
  console.log('Update:')
  console.log('worker.threadId:', struct.threadId)
  console.log('worker.ticks:', struct.ticks)
  console.log('worker.random:', struct.random)
  console.log('worker.src:', struct.buffer.toString('utf-8', 0, struct.bufferLength))
}, 1000)

package.json

{
  "name": "shared-structs-and-workers",
  "version": "0.0.0",
  "description": "Using shared-structs with Workers <3",
  "main": "main.js",
  "scripts": {
    "start": "node --experimental-worker main.js"
  },
  "repository": {
    "type": "git",
    "url": "git+https://gist.github.com/8f5d3076a1afd599cbd9bd5289595179.git"
  },
  "author": "Mathias Buus (@mafintosh)",
  "license": "MIT",
  "bugs": {
    "url": "https://gist.github.com/8f5d3076a1afd599cbd9bd5289595179"
  },
  "homepage": "https://gist.github.com/8f5d3076a1afd599cbd9bd5289595179",
  "dependencies": {
    "shared-structs": "^1.3.2"
  }
}

structs.js

module.exports = require('shared-structs')(`
  struct shared {
    int ticks;
    double random;
    int threadId;
    char buffer[5000];
    uint32_t bufferLength;
  }
`)

worker.js

const { shared } = require('./structs')
const { parentPort, threadId } = require('worker_threads')
const fs = require('fs')

parentPort.once('message', function (buf) {
  const struct = shared(Buffer.from(buf))

  struct.threadId = threadId

  setInterval(function () {
    struct.ticks++
    struct.random = Math.random()
  }, 250)

  setTimeout(function () {
    // read some data into the shared struct
    fs.open(__filename, 'r', function (err, fd) {
      if (err) throw err
      fs.read(fd, struct.buffer, 0, struct.buffer.length, 0, function (err, read) {
        if (err) throw err
        struct.bufferLength = read
      })
    })
  }, 2000)
})