Let‘s see how to do load balancing in Node.js.
Before we start with the solution, you can do a test to see the ability concurrent requests your current machine can handle.
This is our server.js:
const http = require(‘http‘);const pid = process.pid;// listen the mssage event on the global// then do the computationprocess.on(‘message‘, (msg) => { ???const sum = longComputation(); ???process.send(sum);})http.createServer((req, res) => { ???for (let i = 0; i<1e7; i++); // simulate CPU work ???res.end(`Handled by process ${pid}`)}).listen(8000, () => { ???console.log(`Started process ${pid}`);})Test 200 concurrent requests in 10 seconds.
ab -c200 -t10 http:localhost:8000/
For one single node server can handle 51 requsts / second:
Create cluster.js:
// Cluster.jsconst cluster = require(‘cluster‘);const os = require(‘os‘);// For runing for the first time,// Master worker will get started// Then we can fork our new workersif (cluster.isMaster) { ???const cpus = os.cpus().length; ???console.log(`Forking for ${cpus} CPUs`); ???for (let i = 0; i < cpus; i++) { ???????cluster.fork(); ???}} else { ???require(‘./server‘); }For the first time Master worker is running, we just need to create as many workers as our cpus allows. Then next run, we just require our server.js; that‘s it! simple enough!
Running:
node cluster.js
When you refresh the page, you should be able to see, we are assigned to different worker.
Now, if we do the ab testing again:
ab -c200 -t10 http:localhost:8000/
The result is 181 requests/second!
Sometimes it would be ncessary to communcation between master worker and cluster wokers.
Cluster.js:
We can send information from master worker to each cluster worker:
const cluster = require(‘cluster‘);const os = require(‘os‘);// For runing for the first time,// Master worker will get started// Then we can fork our new workersif (cluster.isMaster) { ???const cpus = os.cpus().length; ???console.log(`Forking for ${cpus} CPUs`); ???for (let i = 0; i < cpus; i++) { ???????cluster.fork(); ???} ???console.dir(cluster.workers, {depth: 0}); ???Object.values(cluster.workers).forEach(worker => { ?????? worker.send(`Hello Worker ${worker.id}`); ???})} else { ???require(‘./server‘); }In the server.js, we can listen to the events:
const http = require(‘http‘);const pid = process.pid;// listen the mssage event on the global// then do the computationprocess.on(‘message‘, (msg) => { ???const sum = longComputation(); ???process.send(sum);})http.createServer((req, res) => { ???for (let i = 0; i<1e7; i++); // simulate CPU work ???res.end(`Handled by process ${pid}`)}).listen(8000, () => { ???console.log(`Started process ${pid}`);})process.on(‘message‘, msg => { ???console.log(`Message from master: ${msg}`)})A one patical example would be count users with DB opreations;
// CLuster.jsconst cluster = require(‘cluster‘);const os = require(‘os‘);/** * Mock DB Call */const numberOfUsersDB = function() { ???this.count = this.count || 6; ???this.count = this.count * this.count; ???return this.count;}// For runing for the first time,// Master worker will get started// Then we can fork our new workersif (cluster.isMaster) { ???const cpus = os.cpus().length; ???console.log(`Forking for ${cpus} CPUs`); ???for (let i = 0; i < cpus; i++) { ???????cluster.fork(); ???} ???const updateWorkers = () => { ???????const usersCount = numberOfUsersDB(); ???????Object.values(cluster.workers).forEach(worker => { ???????????worker.send({usersCount}); ???????}); ???} ???updateWorkers(); ???setInterval(updateWorkers, 10000);} else { ???require(‘./server‘);}Here, we let master worker calculate the result, and every 10 seconds we send out the result to all cluster workers.
Then in the server.js, we just need to listen the request:
let usersCount;http.createServer((req, res) => { ???for (let i = 0; i<1e7; i++); // simulate CPU work ???res.write(`Users ${usersCount}`); ???res.end(`Handled by process ${pid}`)}).listen(8000, () => { ???console.log(`Started process ${pid}`);})process.on(‘message‘, msg => { ???usersCount = msg.usersCount;})[Node.js] Load balancing a Http server
原文地址：https://www.cnblogs.com/Answer1215/p/10498717.html