NodeJS集群全局变量

Question

I need to have one common counter for all workers, and everyone could increase it, and that all workers know that the counter has been increased. How can i do that ? All workers can see only local variabless , and only static global variabless.

Answer 1

To accomplish this, you will want to use the cluster module available in Node.js to message between the workers and the master.

Example Code

Here is a working example I just put together. I am using the latest version of Node.js available on the official website ( 9.3.0 ).

const cluster = require('cluster');
const INCREMENT = 'INCREMENT';
const COUNTER = 'COUNTER';


if (cluster.isMaster) {

  cluster.fork();
  cluster.fork();

  let counter = 0;

  cluster.on('message', (worker, msg, handle) => {
    if (msg.topic && msg.topic === INCREMENT) {
      // here we increment the counter
      counter++;
      for (const id in cluster.workers) {
        // Here we notify each worker of the updated value
        cluster.workers[id].send({
          topic: COUNTER,
          value: counter
        });
      }
    }
  });

} else if (cluster.isWorker) {

  console.log(`Worker id: ${cluster.worker.id}`);
  // Here is a function that requests the counter be updated in the master from a worker.
  function incrementCounter() {
    process.send({ topic: INCREMENT });
  }

  // A dummy timeout to call the incrementCounter function
  setTimeout(incrementCounter, 1000 * cluster.worker.id);

  // Handle the counter update
  process.on('message', (msg) => {
    if (msg.topic && msg.topic === COUNTER) {
      console.log(`${cluster.worker.id}/${process.pid}: ${msg.topic} ${msg.value}`);
    }
  });

}

Example Output

Worker id: 1
Worker id: 2
1/1632: COUNTER 1
2/6200: COUNTER 1
2/6200: COUNTER 2
1/1632: COUNTER 2

Official Documentation

Here is the documentation for worker.send(message[, sendHandle][, callback])