保持节点js函数运行而无需使用前端的任何调用

Question

I need to have my NodeJs API to keep creating random data in mongodb.

I am avoiding calling it from from client-end since this should be something happening completely at back-end.

var autoCreate = function(){
  var randomNumb = (Math.random()* (10-0) + 0).toFixed(0);
  var randomThing = randomstring.generate({
    length: randomNumb,
    charset: 'alphabetic'
  });

  Thing.create({
    name: randomThing,
    readByUser: false 
  }, function(err, thing) {
    if(err) { return handleError(res, err); }
  });

  setInterval(function() {
    autoCreate();
  }, randomNumb*1000);
}

But how and where do I call this function for the first time. In my Node API file/controller, I can not just write autoCreate() , It breaks.

What would be the right way of doing it>

Answer 1

As long as there is an active timer, your script will keep on running.

The code in your question has a small flaw, in that it will call setInterval every time the function itself is invoked, but the function itself is never invoked. This means it is not started, and if you were to start it, you will keep adding new intervals right up to the point where the process, the database process or the entire system will crash.

An example using setInterval

function ping() {
  console.log('ping');
}

setInterval(ping, Math.random() * 1000);

Simply start ping -ing with a random interval (where the random time is generated once and used as the interval between ping s)

An example using setTimeout (which is what you seem to want)

function ping() {
  clearTimeout(timer);
  console.log('ping');

  timer = setTimeout(ping, Math.random() * 1000);
}

//  ensure the timer variable exists in the global scope
var timer;
ping();

In this example, you need to start ping -ing yourself and it will just keep invoking itself with random intervals.

Answer 2

Use this function to register your autoCreate call

setTimeout(autoCreate, 1000);

This will register a call to your autoCreate function every 1 sec.

Also make a call to the autoCreate function at the last line of your callback to MongoClient.connect function.

Answer 3

You can call after declaration, no client interaction.

var autoCreate = function(){
    var randomNumb = (Math.random()* (10-0) + 0).toFixed(0);
     var randomThing = randomstring.generate({
    length: randomNumb,
    charset: 'alphabetic'
  });

   Thing.create({
    name: randomThing,
    readByUser: false 
  }, function(err, thing) {
      if(err) { return handleError(res, err); }
    });

   setInterval(function() {
  autoCreate();
  }, randomNumb*1000);

  }

autoCreate(); //Call here 

Answer 4

The best way to automate tasks at backend is to use cron jobs. Here is a module to the rescue node-cron . Here is an example -

  var autoCreate = function(){
    var randomNumb = (Math.random()* (10-0) + 0).toFixed(0);
    var randomThing = randomstring.generate({
      length: randomNumb,
      charset: 'alphabetic'
    });

    Thing.create({
      name: randomThing,
      readByUser: false 
    }, function(err, thing) {
      if(err) { return handleError(res, err); }
    });
  }

var CronJob = require('cron').CronJob;
var job = new CronJob('00 30 11 * * 1-5', function() {
  autoCreate();
  /*
   * Runs every weekday (Monday through Friday)
   * at 11:30:00 AM. It does not run on Saturday
   * or Sunday.
   */
  }, function () {
    /* This function is executed when the job stops */
  },
  true, /* Start the job right now */
  timeZone /* Time zone of this job. */
);

You can set the cron pattern according to your need.