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Race-conditions-web-locks-and-shared-memory

The document discusses parallel programming in Node.js using worker threads, SharedArrayBuffer, and Atomics. It provides an overview of the worker threads API and MessagePort for communication between threads. It describes how to wrap shared memory with classes for object-oriented programming. SharedArrayBuffer can be used with typed array views like Int8Array to access memory in a multithreaded context.

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const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c toString().padStart(width) : cell.padEnd(width); }).join(''))).join }; const proportion = (max, val) => Math.round(val * 100 / max); co calcProportion = table => { table.sort((row1, row2) => row2[DENSITY row1[DENSITY_COL]); const maxDensity = table[0][DENSITY_COL]; table forEach(row => { row.push(proportion(maxDensity, row[DENSITY_COL])) return table; }; const getDataset = file => { const lines = fs.read FileSync(file, 'utf8').toString().split('n'); lines.shift(); lines return lines.map(line => line.split(',')); }; const main = compose (getDataset, calcProportion, renderTable); const fs = require('fs' compose = (...funcs) => x => funcs.reduce((x, fn) => fn(x), x); con DENSITY_COL = 3; const renderTable = table => { const cellWidth = [ 8, 8, 18, 6]; return table.map(row => (row.map((cell, i) => { const = cellWidth[i]; return i ? cell.toString().padStart(width) : cell.p (width); }).join(''))).join('n'); }; const proportion = (max, val) Race conditions, Web Locks & Shared Memory in Node.js Timur Shemsedinov github.com/HowProgrammingWorks github.com/tshemsedinov Chief Technology Architect at Metarhia Lecturer at Kiev Polytechnic Institute
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Why do we need this problems? — Do you know what is mutex, locks, critical section, race condition, parallel programming at all? — Congrats! It’s is very likely that all your JavaScript code broken )))
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Who is at Risk? Parallel programming Threads / Workers, SharedArrayBuffer, Atomics Mutex, Semaphore, Locks other primitives Asynchronous programming Timers, I/O, events, DOM, fetch callbacks, Promise, async/await...
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Who is NOT at Risk? Functional programming Pure functions, no side effects, immutability No transaction scripts, no imperative OOP Specialized data structures Lock-free data structures, wait-free algorithms, Conflict-free data structures, immutable struct
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c How to use workers_threads Node.js: The Road to Workers Anna Henningsen https://youtu.be/pO5a10YPQG4 A Crash Course on Worker Threads Rich Trott https://youtu.be/GRb-XQ5JRA8
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c We are ready for Parallel programming ● Stable worker_threads and messaging API https://nodejs.org/api/worker_threads.html ● Atomics for Compare-and-Swap operations https://developer.mozilla.org/en-US/docs/Web/ JavaScript/Reference/Global_Objects/Atomics ● SharedArrayBuffer to share memory https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/ Global_Objects/SharedArrayBuffer
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Node.js releases with worker_threads 2018-06-20 >=10.5.0 experimental not supported as of now experimental 2019-10-21 stable stable stable
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Web Workers API in browsers Safari 4 2009 Jan 8 (v14, iOS v13.3) Firefox 3.5 2009 Jun 30 (v74, android v68) Android 2.1 2009 Oct 26 (v2.2 - 4.3, v4.4 - 80) Chrome 4 2010 Jan 29 (v80, android v80) Opera 11.5 2011 Jan 28 (v66, android v46) IE 10 2012 Sep 4 (v11) Edge 12 2015 Jul 29 (v80)
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c SharedArrayBuffer support Safari flag v10.1-13 (disabled by default) Firefox flag v57-76 (disabled by default) Androidand Chrome mob (not supported) Chrome flag v60-67 supported v68-80 Opera flag v47-63 supported v64-66 Edge flag v16-18 supported v79-80
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c JavaScript Atomics support Supported started from Node.js 9 ● Atomics ■ add, sub, and, or, xor ■ store, load, exchange, compareExchange ■ notify, wait, wake (deprecated)
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c JavaScript Atomics support Safari v10.1-11, v11.1-13 Firefox flag v46-54, v55-56, flag v57-74 Chrome v60-62, v63-67, v68-80 Edge v16, v17-18, v79-80
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Threads vs Processes process process JavaScript thread V8libuv node.js JavaScript thread V8 libuv node.js JavaScript thread V8 libuv node.js IPC
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c We use threads for... ● CPU-intensive operations ■ Calculations and blocking business-logic ■ Cryptography, parsing, rendering, etc. ● Scaling applications to utilize CPU cores for I/O ■ For example thread per port ● Code isolation related to I/O operations ■ I/O Event loop and thread pool isolation
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Don’t use threads for... Don’t run separate threads for: ● database queries ● external API calls ● timers and waiting for events, like schedulers ● everything with low intensive CPU and I/O Don’t run large number of thread to prevent context switching
● Unhandled exceptions ● Memory leaks and other resources leaks ● In-memory data structures ● Database and other connections ● Environment access, OS, IPC... ● Network descriptors, sockets, ports const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Why Isolation?
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c toString().padStart(width) : cell.padEnd(width); }).join(''))).join }; const proportion = (max, val) => Math.round(val * 100 / max); co calcProportion = table => { table.sort((row1, row2) => row2[DENSITY row1[DENSITY_COL]); const maxDensity = table[0][DENSITY_COL]; table forEach(row => { row.push(proportion(maxDensity, row[DENSITY_COL])) return table; }; const getDataset = file => { const lines = fs.read FileSync(file, 'utf8').toString().split('n'); lines.shift(); lines return lines.map(line => line.split(',')); }; const main = compose (getDataset, calcProportion, renderTable); const fs = require('fs' compose = (...funcs) => x => funcs.reduce((x, fn) => fn(x), x); con DENSITY_COL = 3; const renderTable = table => { const cellWidth = [ 8, 8, 18, 6]; return table.map(row => (row.map((cell, i) => { const = cellWidth[i]; return i ? cell.toString().padStart(width) : cell.p (width); }).join(''))).join('n'); }; const proportion = (max, val) Let’s combine worker threads With JS Atomics and SharedArrayBuffer
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Node.js worker_threads API const threads = require('worker_threads'); const { Worker, isMainThread } = threads; if (isMainThread) { const worker = new Worker( __filename, { workerData: {} } ); } else { const { parentPort } = threads; }
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c MessagePort API worker.on('message', (...args) => {}); worker.on('error', err => {}); worker.on('exit', code => {}); worker.postMessage('Hello there!'); parentPort.postMessage('Hello there!'); parentPort.on('message', (...args) => {}); // MDN Specification // https://developer.mozilla.org/en-US/docs/Web/API/MessagePort
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Wrap Shared Memory with OOP class Point { constructor(buffer, offset) { this.data = new Int8Array(buffer, offset, 2); } get x() { return this.data[0]; } set x(value) { this.data[0] = value; } // ...
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Wrap Shared Memory with OOP // Shared Point instantiation const buffer = new SharedArrayBuffer(64); const point = new Point(buffer, 4); // Now we can read/write fields an instance point.x += 10; point.y = 7; const { x } = point;
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Atomics and SharedArrayBuffer Int8Array, Uint8Array, Int16Array, Uint16Array, Int32Array, Uint32Array
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c ES2017 Atomics prev = Atomics.add(array, index, value) prev = Atomics.sub(array, index, value) prev = Atomics.and(array, index, value) prev = Atomics.or(array, index, value) prev = Atomics.xor(array, index, value)
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Atomics.add(array, index, value) function add(array, index, value) { 1 const prev = array[index]; 2 const sum = prev + value; 3 array[index] = sum; 4 return prev; }
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c ES2017 Atomics (CAS) stored = Atomics.store(array, index, value) value = Atomics.load(array, index) prev = Atomics.exchange(array, index, value) prev = Atomics.compareExchange( array, index, expected, replacement )
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c ES2017 Atomics (notify/wait) woken = Atomics.notify(array, index, count) res = Atomics.wait(array, index, value, [timeout]) res <"ok" | "not-equal" | "timed-out"> array <Int32Array>
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Mutex class Mutex { constructor(shared, offset = 0) enter() leave() } // https://github.com/HowProgrammingWorks/Mutex
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Sync Mutex contract { mutex.enter(); // do something // with shared resources // or data structures mutex.leave(); }
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Mutex constructor constructor(shared, offset = 0) { this.lock = new Int32Array(shared, offset, 1); this.owner = false; } const threads = require('worker_threads'); const { workerData } = threads; const mutex1 = new Mutex(workerData, offset);
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Mutex.enter with Atomics.wait enter() { let prev = Atomics.exchange(this.lock, 0, LOCKED); while (prev !== UNLOCKED) { Atomics.wait(this.lock, 0, LOCKED); prev = Atomics.exchange(this.lock, 0, LOCKED); } this.owner = true; } // Example: 6-blocking.js
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Mutex.leave with Atomics.notify leave() { if (!this.owner) return; Atomics.store(this.lock, 0, UNLOCKED); Atomics.notify(this.lock, 0, 1); this.owner = false; }
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Async Mutex with callback contract mutex.enter(() => { // do something // with shared resources // or data structures mutex.leave(); });
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Async Mutex with async/await contract (async () => { await mutex.enter(); // do something // with shared resources // or data structures mutex.leave(); })();
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Spinlock enter() { return new Promise(resolve => { while (true) { let prev = Atomics.exchange(this.lock, 0, LOCKED); if (prev === UNLOCKED) break; } this.owner = true; resolve(); }); }
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Spinlock with setTimeout enter() { return new Promise(resolve => { const tryEnter = () => { let prev = Atomics.exchange(this.lock, 0, LOCKED); if (prev === UNLOCKED) { this.owner = true; resolve(); } else { setTimeout(tryEnter, 0); } }; tryEnter(); }); }
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Asynchronous Mutex with messaging constructor(messagePort, shared, offset = 0) { this.port = messagePort; this.lock = new Int32Array(shared, offset, 1); this.owner = false; this.trying = false; this.resolve = null; if (messagePort) { messagePort.on('message', kind => { if (kind === 'leave' && this.trying) this.tryEnter(); }); } // Example: 8-async.js }
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Asynchronous Mutex enter() { return new Promise(resolve => { this.resolve = resolve; this.trying = true; this.tryEnter(); }); }
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Asynchronous Mutex tryEnter() { if (!this.resolve) return; let prev = Atomics.exchange(this.lock, 0, LOCKED); if (prev === UNLOCKED) { this.owner = true; this.trying = false; this.resolve(); this.resolve = null; } }
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Thread safe data structures ● Low-level structures e.g. Register, Counter, Buffer, Array, Lists... ● Abstract structures e.g. Queue, Graph, Polyline, etc. ● Subject-domain classes e.g. Sensors, Payment, Biometric data, etc.
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c toString().padStart(width) : cell.padEnd(width); }).join(''))).join }; const proportion = (max, val) => Math.round(val * 100 / max); co calcProportion = table => { table.sort((row1, row2) => row2[DENSITY row1[DENSITY_COL]); const maxDensity = table[0][DENSITY_COL]; table forEach(row => { row.push(proportion(maxDensity, row[DENSITY_COL])) return table; }; const getDataset = file => { const lines = fs.read FileSync(file, 'utf8').toString().split('n'); lines.shift(); lines return lines.map(line => line.split(',')); }; const main = compose (getDataset, calcProportion, renderTable); const fs = require('fs' compose = (...funcs) => x => funcs.reduce((x, fn) => fn(x), x); con DENSITY_COL = 3; const renderTable = table => { const cellWidth = [ 8, 8, 18, 6]; return table.map(row => (row.map((cell, i) => { const = cellWidth[i]; return i ? cell.toString().padStart(width) : cell.p (width); }).join(''))).join('n'); }; const proportion = (max, val) How Race Conditions in single threaded JS are possible?
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Concurrency Problems ● Race condition ● Deadlock ● Livelock ● Resource starvation ● Resource leaks
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c It works on my machine javascruptissinglethreaded
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Don't worry, everything will be random nodejsissinglethreaded
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c I have paws Promises async/await
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Concurrent Computing
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Race Condition class Point { constructor(x, y) { this.x = x; this.y = y; } async move(dx, dy) { this.x = await add(this.x, dx); this.y = await add(this.y, dy); } }
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Race Condition const random = (min, max) => Math .floor(Math.random() * (max - min + 1)) + min; const add = (x, dx) => new Promise(resolve => { setTimeout(() => { resolve(x + dx); }, random(20, 100)); });
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Race Condition const p1 = new Point(10, 10); console.log(p1); p1.move(5, 5); p1.move(6, 6); p1.move(7, 7); p1.move(8, 8); setTimeout(() => { console.log(p1); }, 1000);
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Race Condition Initial Point { x: 10, y: 10 } Expected Point { x: 36, y: 36 } Actual Point { x: 18, y: 25 }
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Race Condition
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Possible Solutions ● Synchronization ■ Resource locking ● Special control flow organization ● Queuing theory ● Actor model ● Use DBMS transactions ● Specialized data structures
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Synchronization Primitives Semaphore Binary semaphore Counting semaphore Condition variable Spinlock Mutex (and locks) Timed mutex Shared mutex Recursive mutex Monitor Barrier
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Semaphore class Semaphore { constructor() enter(callback) leave() } semaphore.enter(() => { // do something semaphore.leave(); }); github.com/HowProgrammingWorks/Semaphore class Semaphore { constructor() async enter() leave() } await semaphore.enter(); // do something semaphore.leave();
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Mutex class Mutex { constructor() async enter() leave() } await mutex.enter(); // do something with shared resources mutex.leave(); https://github.com/HowProgrammingWorks/Mutex
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Resource Locking class Lock { constructor() { this.active = false; this.queue = []; } leave() { if (!this.active) return; this.active = false; const next = this.queue.pop(); if (next) next(); } } enter() { return new Promise(resolve => { const start = () => { this.active = true; resolve(); }; if (!this.active) { start(); return; } this.queue.push(start); }); }
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Resource Locking class Point { constructor(x, y) { this.x = x; this.y = y; this.lock = new Lock(); } async move(dx, dy) { await this.lock.enter(); this.x = await add(this.x, dx); this.y = await add(this.y, dy); this.lock.leave(); } }
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Resource Locking const p1 = new Point(10, 10); console.log(p1); p1.move(5, 5); p1.move(6, 6); p1.move(7, 7); p1.move(8, 8); setTimeout(() => { console.log(p1); }, 1000);
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Resource Locking Initial Point { x: 10, y: 10 } Expected Point { x: 36, y: 36 } Actual Point { x: 36, y: 36 }
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Resource Locking
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Asynchronous Res Locks
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Real-life Example Warehouse API ● Check balances ● Ship goods ● Lock balances github.com/HowProgrammingWorks/RaceCondition
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Web Locks API locks.request('resource', opt, async lock => { if (lock) { // critical section for `resource` // will be released after return } }); https://wicg.github.io/web-locks/
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Web Locks: await (async () => { await something(); await locks.request('resource', async lock => { // critical section for `resource` }); await somethingElse(); })();
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Web Locks: Promise locks.request('resource', lock => new Promise( (resolve, reject) => { // you can store or pass // resolve and reject here } ));
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Web Locks: Thenable locks.request('resource', lock => ({ then((resolve, reject) => { // critical section for `resource` // you can call resolve and reject here }) }));
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Web Locks: Abort const controller = new AbortController(); setTimeout(() => controller.abort(), 2000); const { signal } = controller; locks.request('resource', { signal }, async lock => { // lock is held }).catch(err => { // err is AbortError });
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Web Locks: Timeout locks.request( 'resource', { timeout: 2000 }, async lock => { // lock is held } ).catch(err => { // err is TimeoutError });
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Web Locks for Node.js github.com/nodejs/node/issues/22702 Open github.com/nodejs/node/pull/22719 Closed
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Safe data structures ● Low-level structures e.g. Register, Counter, Buffer, Array, Lists, etc. ● Abstract structures e.g. Queue, Graph, Polyline, etc. ● Subject-domain classes e.g. Sensors, Payment, Biometric data, etc. ● Resources and handles e.g. Sockets, Connections, Streams, etc.
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Deadlock (async () => { await locks.request('A', async lock => { await locks.request('B', async lock => { }); }); })(); (async () => { await locks.request('B', async lock => { await locks.request('A', async lock => { }); }); })();
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Livelock State1 State2 State3 State4
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Alternative Solutions ● Thread safe data structures ● Lock-free data structures ● Wait-free algorithms ● Conflict-free data structures ● Immutable data structures
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Links Spec: wicg.github.io/web-locks MDN: developer.mozilla.org/en-US/docs/Web/API/Web_Locks_API Implementation: github.com/metarhia/web-locks Examples: github.com/HowProgrammingWorks/RaceCondition github.com/HowProgrammingWorks/Semaphore github.com/HowProgrammingWorks/Mutex Async prog: habr.com/ru/post/452974/
const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Contacts github.com/tshemsedinov youtube.com/TimurShemsedinov github.com/HowProgrammingWorks patreon.com/tshemsedinov t.me/HowProgrammingWorks t.me/NodeUA timur.shemsedinov@gmail.com

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Race-conditions-web-locks-and-shared-memory

  • 1.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c toString().padStart(width) : cell.padEnd(width); }).join(''))).join }; const proportion = (max, val) => Math.round(val * 100 / max); co calcProportion = table => { table.sort((row1, row2) => row2[DENSITY row1[DENSITY_COL]); const maxDensity = table[0][DENSITY_COL]; table forEach(row => { row.push(proportion(maxDensity, row[DENSITY_COL])) return table; }; const getDataset = file => { const lines = fs.read FileSync(file, 'utf8').toString().split('n'); lines.shift(); lines return lines.map(line => line.split(',')); }; const main = compose (getDataset, calcProportion, renderTable); const fs = require('fs' compose = (...funcs) => x => funcs.reduce((x, fn) => fn(x), x); con DENSITY_COL = 3; const renderTable = table => { const cellWidth = [ 8, 8, 18, 6]; return table.map(row => (row.map((cell, i) => { const = cellWidth[i]; return i ? cell.toString().padStart(width) : cell.p (width); }).join(''))).join('n'); }; const proportion = (max, val) Race conditions, Web Locks & Shared Memory in Node.js Timur Shemsedinov github.com/HowProgrammingWorks github.com/tshemsedinov Chief Technology Architect at Metarhia Lecturer at Kiev Polytechnic Institute
  • 2.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Why do we need this problems? — Do you know what is mutex, locks, critical section, race condition, parallel programming at all? — Congrats! It’s is very likely that all your JavaScript code broken )))
  • 3.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Who is at Risk? Parallel programming Threads / Workers, SharedArrayBuffer, Atomics Mutex, Semaphore, Locks other primitives Asynchronous programming Timers, I/O, events, DOM, fetch callbacks, Promise, async/await...
  • 4.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Who is NOT at Risk? Functional programming Pure functions, no side effects, immutability No transaction scripts, no imperative OOP Specialized data structures Lock-free data structures, wait-free algorithms, Conflict-free data structures, immutable struct
  • 5.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c How to use workers_threads Node.js: The Road to Workers Anna Henningsen https://youtu.be/pO5a10YPQG4 A Crash Course on Worker Threads Rich Trott https://youtu.be/GRb-XQ5JRA8
  • 6.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c We are ready for Parallel programming ● Stable worker_threads and messaging API https://nodejs.org/api/worker_threads.html ● Atomics for Compare-and-Swap operations https://developer.mozilla.org/en-US/docs/Web/ JavaScript/Reference/Global_Objects/Atomics ● SharedArrayBuffer to share memory https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/ Global_Objects/SharedArrayBuffer
  • 7.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Node.js releases with worker_threads 2018-06-20 >=10.5.0 experimental not supported as of now experimental 2019-10-21 stable stable stable
  • 8.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Web Workers API in browsers Safari 4 2009 Jan 8 (v14, iOS v13.3) Firefox 3.5 2009 Jun 30 (v74, android v68) Android 2.1 2009 Oct 26 (v2.2 - 4.3, v4.4 - 80) Chrome 4 2010 Jan 29 (v80, android v80) Opera 11.5 2011 Jan 28 (v66, android v46) IE 10 2012 Sep 4 (v11) Edge 12 2015 Jul 29 (v80)
  • 9.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c SharedArrayBuffer support Safari flag v10.1-13 (disabled by default) Firefox flag v57-76 (disabled by default) Androidand Chrome mob (not supported) Chrome flag v60-67 supported v68-80 Opera flag v47-63 supported v64-66 Edge flag v16-18 supported v79-80
  • 10.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c JavaScript Atomics support Supported started from Node.js 9 ● Atomics ■ add, sub, and, or, xor ■ store, load, exchange, compareExchange ■ notify, wait, wake (deprecated)
  • 11.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c JavaScript Atomics support Safari v10.1-11, v11.1-13 Firefox flag v46-54, v55-56, flag v57-74 Chrome v60-62, v63-67, v68-80 Edge v16, v17-18, v79-80
  • 12.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Threads vs Processes process process JavaScript thread V8libuv node.js JavaScript thread V8 libuv node.js JavaScript thread V8 libuv node.js IPC
  • 13.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c We use threads for... ● CPU-intensive operations ■ Calculations and blocking business-logic ■ Cryptography, parsing, rendering, etc. ● Scaling applications to utilize CPU cores for I/O ■ For example thread per port ● Code isolation related to I/O operations ■ I/O Event loop and thread pool isolation
  • 14.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Don’t use threads for... Don’t run separate threads for: ● database queries ● external API calls ● timers and waiting for events, like schedulers ● everything with low intensive CPU and I/O Don’t run large number of thread to prevent context switching
  • 15.
    ● Unhandled exceptions ●Memory leaks and other resources leaks ● In-memory data structures ● Database and other connections ● Environment access, OS, IPC... ● Network descriptors, sockets, ports const fs = require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Why Isolation?
  • 16.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c toString().padStart(width) : cell.padEnd(width); }).join(''))).join }; const proportion = (max, val) => Math.round(val * 100 / max); co calcProportion = table => { table.sort((row1, row2) => row2[DENSITY row1[DENSITY_COL]); const maxDensity = table[0][DENSITY_COL]; table forEach(row => { row.push(proportion(maxDensity, row[DENSITY_COL])) return table; }; const getDataset = file => { const lines = fs.read FileSync(file, 'utf8').toString().split('n'); lines.shift(); lines return lines.map(line => line.split(',')); }; const main = compose (getDataset, calcProportion, renderTable); const fs = require('fs' compose = (...funcs) => x => funcs.reduce((x, fn) => fn(x), x); con DENSITY_COL = 3; const renderTable = table => { const cellWidth = [ 8, 8, 18, 6]; return table.map(row => (row.map((cell, i) => { const = cellWidth[i]; return i ? cell.toString().padStart(width) : cell.p (width); }).join(''))).join('n'); }; const proportion = (max, val) Let’s combine worker threads With JS Atomics and SharedArrayBuffer
  • 17.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Node.js worker_threads API const threads = require('worker_threads'); const { Worker, isMainThread } = threads; if (isMainThread) { const worker = new Worker( __filename, { workerData: {} } ); } else { const { parentPort } = threads; }
  • 18.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c MessagePort API worker.on('message', (...args) => {}); worker.on('error', err => {}); worker.on('exit', code => {}); worker.postMessage('Hello there!'); parentPort.postMessage('Hello there!'); parentPort.on('message', (...args) => {}); // MDN Specification // https://developer.mozilla.org/en-US/docs/Web/API/MessagePort
  • 19.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Wrap Shared Memory with OOP class Point { constructor(buffer, offset) { this.data = new Int8Array(buffer, offset, 2); } get x() { return this.data[0]; } set x(value) { this.data[0] = value; } // ...
  • 20.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Wrap Shared Memory with OOP // Shared Point instantiation const buffer = new SharedArrayBuffer(64); const point = new Point(buffer, 4); // Now we can read/write fields an instance point.x += 10; point.y = 7; const { x } = point;
  • 21.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Atomics and SharedArrayBuffer Int8Array, Uint8Array, Int16Array, Uint16Array, Int32Array, Uint32Array
  • 22.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c ES2017 Atomics prev = Atomics.add(array, index, value) prev = Atomics.sub(array, index, value) prev = Atomics.and(array, index, value) prev = Atomics.or(array, index, value) prev = Atomics.xor(array, index, value)
  • 23.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Atomics.add(array, index, value) function add(array, index, value) { 1 const prev = array[index]; 2 const sum = prev + value; 3 array[index] = sum; 4 return prev; }
  • 24.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c ES2017 Atomics (CAS) stored = Atomics.store(array, index, value) value = Atomics.load(array, index) prev = Atomics.exchange(array, index, value) prev = Atomics.compareExchange( array, index, expected, replacement )
  • 25.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c ES2017 Atomics (notify/wait) woken = Atomics.notify(array, index, count) res = Atomics.wait(array, index, value, [timeout]) res <"ok" | "not-equal" | "timed-out"> array <Int32Array>
  • 26.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Mutex class Mutex { constructor(shared, offset = 0) enter() leave() } // https://github.com/HowProgrammingWorks/Mutex
  • 27.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Sync Mutex contract { mutex.enter(); // do something // with shared resources // or data structures mutex.leave(); }
  • 28.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Mutex constructor constructor(shared, offset = 0) { this.lock = new Int32Array(shared, offset, 1); this.owner = false; } const threads = require('worker_threads'); const { workerData } = threads; const mutex1 = new Mutex(workerData, offset);
  • 29.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Mutex.enter with Atomics.wait enter() { let prev = Atomics.exchange(this.lock, 0, LOCKED); while (prev !== UNLOCKED) { Atomics.wait(this.lock, 0, LOCKED); prev = Atomics.exchange(this.lock, 0, LOCKED); } this.owner = true; } // Example: 6-blocking.js
  • 30.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Mutex.leave with Atomics.notify leave() { if (!this.owner) return; Atomics.store(this.lock, 0, UNLOCKED); Atomics.notify(this.lock, 0, 1); this.owner = false; }
  • 31.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Async Mutex with callback contract mutex.enter(() => { // do something // with shared resources // or data structures mutex.leave(); });
  • 32.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Async Mutex with async/await contract (async () => { await mutex.enter(); // do something // with shared resources // or data structures mutex.leave(); })();
  • 33.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Spinlock enter() { return new Promise(resolve => { while (true) { let prev = Atomics.exchange(this.lock, 0, LOCKED); if (prev === UNLOCKED) break; } this.owner = true; resolve(); }); }
  • 34.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Spinlock with setTimeout enter() { return new Promise(resolve => { const tryEnter = () => { let prev = Atomics.exchange(this.lock, 0, LOCKED); if (prev === UNLOCKED) { this.owner = true; resolve(); } else { setTimeout(tryEnter, 0); } }; tryEnter(); }); }
  • 35.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Asynchronous Mutex with messaging constructor(messagePort, shared, offset = 0) { this.port = messagePort; this.lock = new Int32Array(shared, offset, 1); this.owner = false; this.trying = false; this.resolve = null; if (messagePort) { messagePort.on('message', kind => { if (kind === 'leave' && this.trying) this.tryEnter(); }); } // Example: 8-async.js }
  • 36.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Asynchronous Mutex enter() { return new Promise(resolve => { this.resolve = resolve; this.trying = true; this.tryEnter(); }); }
  • 37.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Asynchronous Mutex tryEnter() { if (!this.resolve) return; let prev = Atomics.exchange(this.lock, 0, LOCKED); if (prev === UNLOCKED) { this.owner = true; this.trying = false; this.resolve(); this.resolve = null; } }
  • 38.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Thread safe data structures ● Low-level structures e.g. Register, Counter, Buffer, Array, Lists... ● Abstract structures e.g. Queue, Graph, Polyline, etc. ● Subject-domain classes e.g. Sensors, Payment, Biometric data, etc.
  • 39.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c toString().padStart(width) : cell.padEnd(width); }).join(''))).join }; const proportion = (max, val) => Math.round(val * 100 / max); co calcProportion = table => { table.sort((row1, row2) => row2[DENSITY row1[DENSITY_COL]); const maxDensity = table[0][DENSITY_COL]; table forEach(row => { row.push(proportion(maxDensity, row[DENSITY_COL])) return table; }; const getDataset = file => { const lines = fs.read FileSync(file, 'utf8').toString().split('n'); lines.shift(); lines return lines.map(line => line.split(',')); }; const main = compose (getDataset, calcProportion, renderTable); const fs = require('fs' compose = (...funcs) => x => funcs.reduce((x, fn) => fn(x), x); con DENSITY_COL = 3; const renderTable = table => { const cellWidth = [ 8, 8, 18, 6]; return table.map(row => (row.map((cell, i) => { const = cellWidth[i]; return i ? cell.toString().padStart(width) : cell.p (width); }).join(''))).join('n'); }; const proportion = (max, val) How Race Conditions in single threaded JS are possible?
  • 40.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Concurrency Problems ● Race condition ● Deadlock ● Livelock ● Resource starvation ● Resource leaks
  • 41.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c It works on my machine javascruptissinglethreaded
  • 42.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Don't worry, everything will be random nodejsissinglethreaded
  • 43.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c I have paws Promises async/await
  • 44.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Concurrent Computing
  • 45.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Race Condition class Point { constructor(x, y) { this.x = x; this.y = y; } async move(dx, dy) { this.x = await add(this.x, dx); this.y = await add(this.y, dy); } }
  • 46.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Race Condition const random = (min, max) => Math .floor(Math.random() * (max - min + 1)) + min; const add = (x, dx) => new Promise(resolve => { setTimeout(() => { resolve(x + dx); }, random(20, 100)); });
  • 47.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Race Condition const p1 = new Point(10, 10); console.log(p1); p1.move(5, 5); p1.move(6, 6); p1.move(7, 7); p1.move(8, 8); setTimeout(() => { console.log(p1); }, 1000);
  • 48.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Race Condition Initial Point { x: 10, y: 10 } Expected Point { x: 36, y: 36 } Actual Point { x: 18, y: 25 }
  • 49.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Race Condition
  • 50.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Possible Solutions ● Synchronization ■ Resource locking ● Special control flow organization ● Queuing theory ● Actor model ● Use DBMS transactions ● Specialized data structures
  • 51.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Synchronization Primitives Semaphore Binary semaphore Counting semaphore Condition variable Spinlock Mutex (and locks) Timed mutex Shared mutex Recursive mutex Monitor Barrier
  • 52.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Semaphore class Semaphore { constructor() enter(callback) leave() } semaphore.enter(() => { // do something semaphore.leave(); }); github.com/HowProgrammingWorks/Semaphore class Semaphore { constructor() async enter() leave() } await semaphore.enter(); // do something semaphore.leave();
  • 53.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Mutex class Mutex { constructor() async enter() leave() } await mutex.enter(); // do something with shared resources mutex.leave(); https://github.com/HowProgrammingWorks/Mutex
  • 54.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Resource Locking class Lock { constructor() { this.active = false; this.queue = []; } leave() { if (!this.active) return; this.active = false; const next = this.queue.pop(); if (next) next(); } } enter() { return new Promise(resolve => { const start = () => { this.active = true; resolve(); }; if (!this.active) { start(); return; } this.queue.push(start); }); }
  • 55.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Resource Locking class Point { constructor(x, y) { this.x = x; this.y = y; this.lock = new Lock(); } async move(dx, dy) { await this.lock.enter(); this.x = await add(this.x, dx); this.y = await add(this.y, dy); this.lock.leave(); } }
  • 56.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Resource Locking const p1 = new Point(10, 10); console.log(p1); p1.move(5, 5); p1.move(6, 6); p1.move(7, 7); p1.move(8, 8); setTimeout(() => { console.log(p1); }, 1000);
  • 57.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Resource Locking Initial Point { x: 10, y: 10 } Expected Point { x: 36, y: 36 } Actual Point { x: 36, y: 36 }
  • 58.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Resource Locking
  • 59.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Asynchronous Res Locks
  • 60.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Real-life Example Warehouse API ● Check balances ● Ship goods ● Lock balances github.com/HowProgrammingWorks/RaceCondition
  • 61.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Web Locks API locks.request('resource', opt, async lock => { if (lock) { // critical section for `resource` // will be released after return } }); https://wicg.github.io/web-locks/
  • 62.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Web Locks: await (async () => { await something(); await locks.request('resource', async lock => { // critical section for `resource` }); await somethingElse(); })();
  • 63.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Web Locks: Promise locks.request('resource', lock => new Promise( (resolve, reject) => { // you can store or pass // resolve and reject here } ));
  • 64.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Web Locks: Thenable locks.request('resource', lock => ({ then((resolve, reject) => { // critical section for `resource` // you can call resolve and reject here }) }));
  • 65.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Web Locks: Abort const controller = new AbortController(); setTimeout(() => controller.abort(), 2000); const { signal } = controller; locks.request('resource', { signal }, async lock => { // lock is held }).catch(err => { // err is AbortError });
  • 66.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Web Locks: Timeout locks.request( 'resource', { timeout: 2000 }, async lock => { // lock is held } ).catch(err => { // err is TimeoutError });
  • 67.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Web Locks for Node.js github.com/nodejs/node/issues/22702 Open github.com/nodejs/node/pull/22719 Closed
  • 68.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Safe data structures ● Low-level structures e.g. Register, Counter, Buffer, Array, Lists, etc. ● Abstract structures e.g. Queue, Graph, Polyline, etc. ● Subject-domain classes e.g. Sensors, Payment, Biometric data, etc. ● Resources and handles e.g. Sockets, Connections, Streams, etc.
  • 69.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Deadlock (async () => { await locks.request('A', async lock => { await locks.request('B', async lock => { }); }); })(); (async () => { await locks.request('B', async lock => { await locks.request('A', async lock => { }); }); })();
  • 70.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Livelock State1 State2 State3 State4
  • 71.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Alternative Solutions ● Thread safe data structures ● Lock-free data structures ● Wait-free algorithms ● Conflict-free data structures ● Immutable data structures
  • 72.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Links Spec: wicg.github.io/web-locks MDN: developer.mozilla.org/en-US/docs/Web/API/Web_Locks_API Implementation: github.com/metarhia/web-locks Examples: github.com/HowProgrammingWorks/RaceCondition github.com/HowProgrammingWorks/Semaphore github.com/HowProgrammingWorks/Mutex Async prog: habr.com/ru/post/452974/
  • 73.
    const fs =require('fs'); const compose = (...funcs) => x => funcs. reduce((x, fn) => fn(x), x); const DENSITY_COL = 3; const renderTab table => { const cellWidth = [18, 10, 8, 8, 18, 6]; return table.ma => (row.map((cell, i) => { const width = cellWidth[i]; return i ? c Contacts github.com/tshemsedinov youtube.com/TimurShemsedinov github.com/HowProgrammingWorks patreon.com/tshemsedinov t.me/HowProgrammingWorks t.me/NodeUA timur.shemsedinov@gmail.com