How to sleep the thread in node.js without affecting other threads?


Question

As per Understanding the node.js event loop, node.js supports a single thread model. That means if I make multiple requests to a node.js server, it won't spawn a new thread for each request but will execute each request one by one. It means if I do the following for the first request in my node.js code, and meanwhile a new request comes in on node, the second request has to wait until the first request completes, including 5 second sleep time. Right?

var sleep = require('sleep');
    sleep.sleep(5)//sleep for 5 seconds

Is there a way that node.js can spawn a new thread for each request so that the second request does not have to wait for the first request to complete, or can I call sleep on specific thread only?

1
58
5/30/2013 9:40:16 PM

Accepted Answer

If you are referring to the npm module sleep, it notes in the readme that sleep will block execution. So you are right - it isn't what you want. Instead you want to use setTimeout which is non-blocking. Here is an example:

setTimeout(function() {
  console.log('hello world!');
}, 5000);

For anyone looking to do this using es7 async/await, this example should help:

const snooze = ms => new Promise(resolve => setTimeout(resolve, ms));

const example = async () => {
  console.log('About to snooze without halting the event loop...');
  await snooze(1000);
  console.log('done!');
};

example();
124
5/18/2017 9:15:51 PM

In case you have a loop with an async request in each one and you want a certain time between each request you can use this code:

   var startTimeout = function(timeout, i){
        setTimeout(function() {
            myAsyncFunc(i).then(function(data){
                console.log(data);
            })
        }, timeout);
   }

   var myFunc = function(){
        timeout = 0;
        i = 0;
        while(i < 10){
            // By calling a function, the i-value is going to be 1.. 10 and not always 10
            startTimeout(timeout, i);
            // Increase timeout by 1 sec after each call
            timeout += 1000;
            i++;
        }
    }

This examples waits 1 second after each request before sending the next one.


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