Server side timer after meteor collection is updated

Question

I'm currently developping a simple realtime multiplayer game and i'm stuck with the timer logic.

When there are enough players in a game, the status of the game is set to "STARTED" and from there i want to start a 10 seconds timer and show it to all the clients.

My idea is to use collection hooks and call a setTimeout after the collection update. But I don't really know how to do it and if it is the best solution.

Also maybe should I use cron instead of timers?

Answer 1

I would use the following logic :

• before.update hook on your collection to update the status to Started using collection hooks

• set a datetime in the hook for the date when players were enough => save this data in your Game Collection

  Game.before.update(function (userId, doc, fieldNames, modifier, options) {
      if (modifier && modifier.$set && modifier.$set.nb_of_players > 10) {
          modifier.$set.status = "Started";
          modifier.$set.startingTime = new Date();
      }
  });
  

• use a helper to compute dynamically the time to show on your client, here a basic working example of reactive time display, that you need to improve to get a countdown:

  Template.Home.helpers({
      time: function () {
          return Template.instance().date.get();
      },
  });
  
  
  Template.Home.onCreated(function () {
      var self = Template.instance();
      self.date = new ReactiveVar();
      Meteor.setInterval(function () {
          self.date.set(new Date());
      }, 1);
  
  });
  

• use a setTimeout to actually do something 10 seconds later - this should be called after setting the game to started. Either in an autorun checking the value, or in the callback function of the Meteor.call you use :

  Meteor.setTimeout(function(){
      Meteor.call("launchAction", {data:data}, function (error, result) {
          if (error){
              console.error(error);
          } else {
  
          }
      });
  }, 10);
  

  I also recommend using momentjs to actually manipulate dates and times