I don't understand how clusters work in Node.
The snippet below is example code from Node's docs.
const cluster = require('cluster');
const http = require('http');
const numCPUs = require('os').cpus().length;
if (cluster.isMaster) {
console.log(`Master ${process.pid} is running`);
// Fork workers.
for (let i = 0; i < numCPUs; i++) {
cluster.fork();
}
cluster.on('exit', (worker, code, signal) => {
console.log(`worker ${worker.process.pid} died`);
});
} else {
// Workers can share any TCP connection
// In this case it is an HTTP server
http.createServer((req, res) => {
res.writeHead(200);
res.end('hello world\n');
}).listen(8000);
console.log(`Worker ${process.pid} started`);
}
I'd like to know exactly what happens at cluster.fork()
. Does it copy over any variables to the forked processes? If I declared an object before forking, would both threads access it? Is it possible to assign tasks to a thread manually or does Node have to do it?
via Lolums
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