How to implement multi-threading in nodejs

Although Node.js is single-threaded, it can simulate multi-threading in many ways: 1. Worker thread: independently create threads to perform tasks; 2. Cluster module: create multiple worker processes for parallel processing; 3. Event loop : Arrange tasks into the event loop for non-blocking execution.

How to implement multi-threading in Node.js?

Node.js is a single-threaded running environment, which means it can only handle one task at a time. However, multi-threading can be simulated by:

1. Worker threads

Node.js 10.5 and later introduces Worker threads, which allow the creation of independent thread to perform time-consuming tasks, thereby releasing the main thread. Worker threads have the following advantages:

• Isolated from the main thread, so they do not block the main thread.
• Can communicate with the main thread through channels.
• Using shared memory by default can improve performance.

2. Cluster module

The Cluster module allows the creation of multiple worker processes, each with its own event loop. The main process is responsible for assigning tasks to worker processes, and the worker processes are responsible for processing tasks. The Cluster module has the following advantages:

• Execute tasks in parallel across processes.
• Improve scalability and throughput.
• Can automatically restart failed worker processes.

3. Event loop

The operation of Node.js is based on the event loop, which is a continuously running loop that constantly checks whether there are any pending tasks. Tasks can be I/O operations, timers, or user code. Non-blocking execution is achieved by scheduling time-consuming tasks into the event loop, freeing up the main thread.

Specific implementation

Use Worker thread:

<code class="js">// 创建一个 worker 线程
const worker = new Worker('./worker.js');

// 监听 worker 线程的消息
worker.addEventListener('message', (event) => {
  console.log('Received message from worker:', event.data);
});

// 向 worker 线程发送消息
worker.postMessage({ message: 'Hello from main thread!' });</code>

Use Cluster module:

<code class="js">// 创建一个 cluster 监听器
const cluster = require('cluster');

// 如果是主进程，则创建 worker 进程
if (cluster.isMaster) {
  for (let i = 0; i < numCPUs; i++) {
    cluster.fork();
  }
} else {
  // 如果是 worker 进程，则执行任务
  console.log(`Worker ${cluster.worker.id} started`);
  performTask();
}</code>

Use event loop:

<code class="js">// 安排一个耗时任务到事件循环
setTimeout(() => {
  console.log('耗时任务完成');
}, 1000);</code>

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