![Sharing Memory Between Threads
const i32Array = new Int32Array(new SharedArrayBuffer(12));
if (isMainThread) {
console.log(i32Array); // Int32Array [ 0, 0, 0 ]
const w = new Worker(__filename, {
workerData: i32Array
});
w.once('message', () => console.log(i32Array)); // Int32Array [ 1, 0, 0 ]
} else {
const data = require('worker_threads').workerData;
data[0] = 1;
parentPort.postMessage('Done');
}](https://image.slidesharecdn.com/threadsnode-190527103936/85/Threads-and-Node-js-16-320.jpg)
![Atomics and Mutable Shared Arrays
const i32Array = new Int32Array(new SharedArrayBuffer(12));
if (isMainThread) {
console.log(i32Array); // Int32Array [ 0, 0, 0 ]
const w = new Worker(__filename, {
workerData: i32Array
});
w.once('message', () => console.log(Atomics.load(i32Array, 0))); // 1
} else {
const data = require('worker_threads').workerData;
data[0] = 1;
parentPort.postMessage('Done');
}](https://image.slidesharecdn.com/threadsnode-190527103936/85/Threads-and-Node-js-18-320.jpg)
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Threads and Node.js
- 1. Threads and Node.js Sakthipriyan Vairamani Node.js Technical Steering Committee Member
- 2. Concurrency vs Parallelism ● Parallelism ○ Multiple execution units ○ Simultaneous execution ● Concurrency ○ Single execution unit ○ Time interleaved execution
- 3. Concurrency vs Parallelism No concurrency, no parallelism 1 2 3 1 2 3 1 2 3 CPU Cycles CPU 1 Concurrency, no parallelism 1 1 1 2 2 2 3 3 3 CPU Cycles CPU 1 No concurrency, parallelism 1 2 3 1 2 3 1 2 3 CPU Cycles CPU 1 CPU 2 CPU 3 Concurrency, parallelism 1 2 3 1 2 3 1 2 3 CPU Cycles CPU 1 CPU 2 CPU 3
- 4. Execution Models ● Single tasking ○ One program, runs to completion ● Multi tasking ○ Co-operative ○ Pre-emptive ○ Multi Core
- 5. Process ● An instance of a program ○ Just like how objects are to classes ● Container for ○ Code ○ Memory (Stack, Heap, Data segment) ○ Resource Descriptors ○ State (Execution Context)
- 6. Process Code Resource Descriptors Heap Execution Context (Stack + Registers) Main Thread
- 7. Thread ● Execution Context ○ Registers ○ Stack ● Associated with a process ● Share process’s resources and memory ● Can be multiple for a process
- 8. Thread Code, Resources, and Heap Context Main Thread Context Context Thread 1 Thread 2
- 9. Node.js ● Single threaded ● Non-blocking IO ● Async APIs with callbacks ● Scalable ● Never block Node.js’s main thread
- 10. Node.js’s Asynchronicity and Threads Event Loop libuv Thread PoolNode.js APIs Userland JavaScript code 1 2 3
- 11. Node.js Worker Threads ● CPU Intensive Tasks ● Share main process’s resources, but not variables ● Can Share SharedArrayBuffer ● Message Passing ● Structured Cloning
- 12. Creating Worker Threads // DO NOT RUN THIS const { Worker } = require('worker_threads'); const w = new Worker(__filename);
- 13. Detect Main & Worker Threads const { isMainThread, Worker } = require('worker_threads'); if (isMainThread) { console.log('Inside Main Thread'); const w = new Worker(__filename); } else { console.log('Inside Worker Thread'); }
- 14. Pass initial context during Thread Creation if (isMainThread) { const w = new Worker(__filename, { workerData: { data: 'Node.js' } }); } else { console.log(require('worker_threads').workerData); }
- 15. Communication between Main and Worker Threads const { isMainThread, parentPort, Worker } = require('worker_threads'); if (isMainThread) { const w = new Worker(__filename); w.postMessage('Ping'); w.once('message', console.log); w.on('exit', (exitCode) => console.log(exitCode)); } else { parentPort.once('message', function (msg) { if (msg === 'Ping') parentPort.postMessage('Pong'); }); }
- 16. Sharing Memory Between Threads const i32Array = new Int32Array(new SharedArrayBuffer(12)); if (isMainThread) { console.log(i32Array); // Int32Array [ 0, 0, 0 ] const w = new Worker(__filename, { workerData: i32Array }); w.once('message', () => console.log(i32Array)); // Int32Array [ 1, 0, 0 ] } else { const data = require('worker_threads').workerData; data[0] = 1; parentPort.postMessage('Done'); }
- 17. ● Atomic operations on SharedArrayBuffers ● Bunch of static functions ○ Atomics.store(sab, index, value) ○ Atomics.load(sab, index) ○ Atomics.add(sab, index, value) ○ ... Atomics
- 18. Atomics and Mutable Shared Arrays const i32Array = new Int32Array(new SharedArrayBuffer(12)); if (isMainThread) { console.log(i32Array); // Int32Array [ 0, 0, 0 ] const w = new Worker(__filename, { workerData: i32Array }); w.once('message', () => console.log(Atomics.load(i32Array, 0))); // 1 } else { const data = require('worker_threads').workerData; data[0] = 1; parentPort.postMessage('Done'); }
- 19. Terminating Worker Threads if (isMainThread) { const w = new Worker(__filename); console.log(w.threadId); // 1 w.postMessage(w.threadId); w.once('message', (id) => { console.log('Thread ID is', id); w.terminate(); }); w.on('exit', console.log); // 0 } else { parentPort.once('message', (msg) => { let i = 0; while (true) { if (i++ === 10) { parentPort.postMessage(require('worker_threads').threadId); break; // Uncomment to change exit code }
- 20. The Structured Clone Algorithm ● Clone/copy of the object ● Used during postMessage ● Error and Function cannot be cloned ● Property Descriptors, Setters, and Getters are ignored ● Prototype chain is ignored
- 21. Thank you! Sakthipriyan Vairamani Node.js Technical Steering Committee Member