Nodejs enables multi process and inter process communication

JS Whether in browser or Node The environment is single threaded , But you can call API Open multiple processes to improve the utilization of hardware resources .
The following is an introduction to nodejs The way to start multiple processes and realize communication .

process vs Threads

process ： Resource allocation Minimum unit of
Threads ：CPU Dispatch Minimum unit of

Start sub process mode

• child_process.fork
• cluster.fork

communication mode

Use send and on The message

Usage scenarios in two ways

child_process.fork： Used to start a single calculation , Complete the work with large amount of calculation
cluster： Integrate , It is applicable to the scenario where multiple processes start multiple network services

Code

Mode one ： child_process.fork

The main process process.js

const http = require('http')
const fork = require('child_process').fork
const server = http.createServer((req, res) => {
    
    if (req.url == "/get-sum") {
    
        console.log(' The main process id', process.pid);
        //  Start subprocess 
        const computedProcess = fork('./computed.js')
        computedProcess.send(' Start calculating ')
        computedProcess.on('message', data => {
    
            console.log(' Information received by the main process ', data);
            res.end('sum is ' + data)
        })
        computedProcess.on('close', () => {
    
            console.log(' The subprocess exited due to an error ')
            computedProcess.kill()
            res.end('error')
        })
    }
})
server.listen(3000, () => {
    
    console.log('http://localhost:3000');
})

Subprocesses computed.js

function getSum() {
    
    let sum = 0
    for (let i = 0; i < 10000; i++) {
    
        sum += i
    }
    return sum
}
process.on('message', data => {
    
    console.log(' Subprocesses id', process.pid);
    console.log(' The information received by the child process ', data);
    const sum = getSum()
    //  Send a message to the main process 
    process.send(sum)

})

Mode two ：cluster.fork

const http = require('http')
const cpuCoreLength = require('os').cpus().length
const cluster = require('cluster')

if (cluster.isMaster) {
    
    for (let i = 0; i < cpuCoreLength; i++) {
    
        cluster.fork() //  Start subprocess 
    }
    cluster.on('exit', worker => {
    
        console.log(' Subprocess exit ');
        cluster.fork() //  Process daemons 
    })
} else {
    
    //  Multiple child processes will share one TCP Connect , Provide a web service 
    const server = http.createServer((req, res) => {
    
        res.writeHead(200)
        res.end('done')
    })
    server.listen(3000)
}

//  In the work  PM2