I'm playing with realtime whiteboards with meteor. My first attempt was working very well, if you open 2 browsers and draw in one of them, the other one updates in a few milliseconds ( http://pen.meteor.com/stackoverflow )
Now, my second project, is to make an infinite realtime whiteboard. The main thing that changes now, is that all lines are grouped by zones, and the viewer only subscribe to the lines in the visible zones. And now there is a dealy of 5 seconds (!) when you do something in one browser to see it happen in the other one ( http://carve.meteor.com/love ).
I've tried to add indexes in the mongo database for the fields determining the zones.
I've tried updating the Collection only for a full line (and not each time I push a new point like i my first project).
I've tried adding a timeout not to subscribe too often when scrolling or zooming the board.
Nothing changes, always a 5 seconds delay.
I don't have this delay when working locally.
Here is the piece of code responsible for subscribing to the lines you the visible area :
subscribeTimeout=false;
Deps.autorun(function () {
var vT=Session.get("visible_tiles");
var board_key=Session.get("board_key");
if (subscribeTimeout) Meteor.clearTimeout(subscribeTimeout);
subscribeTimeout=Meteor.setTimeout(subscribeLines, 500);
});
function subscribeLines() {
subscribeTimeout=false;
var vT=Session.get("visible_tiles");
console.log("SUBSCRIBE");
Meteor.subscribe("board_lines", Session.get("board_key"),vT.left,vT.right,vT.top,vT.bottom, function() {
console.log("subscribe board_lines "+Session.get("board_key"));
});
}
I've been a SysAdmin for 15 years. Without running the code, it sounds like an imposed limitation of the meteor.com server. They probably put in delays on the resources so everyone gets a fair share. I'd publish to another server like heroku for an easy deploy or manually to another server like linode or my favorite Joyent. Alternatively you could try and contact meteor.com directly and ask them if/how they limit resource usage.
Since the code runs fast/instantly locally, you should see sub-second response times from a good server over a good network.
Related
I'm working on adding a requested feature to my SPA. We have some users who leave their tabs open to our application for long periods of time. We also push out frequent updates (sometimes 5x a day, as we're pre-revenue). I'm wondering if it's possible to modify the serviceWorker that comes installed with Create-React-App to run a polling loop (maybe every 10 minutes) to poll for new updates to the application, instead of only on initial page load.
This way, a user who leaves their tab open could receive update notifications without having to refresh.
Has anyone achieved something like this before, and know how I might implement that into the CRA serviceWorker?
Figured it out! In the registerServiceWorker.js file, I added a simple setInterval inside the callback for the navigator.serviceWorker.register() function:
// poll for live updates to the serviceWorker
pollingLoopInterval = setInterval(async () => {
await registration.update();
}, POLLING_LOOP_MS);
Easy!
So I've this project for school who is about "triggers" for social networks.
Let me explain:
- A user can register for our application and login
- He can sign in for multiple services like Facebook, Twitter etc.
- Then their is what we call triggers, once he signed in on our application and registered his services, everytime he will post something on twitter for example my server will see it and post it on Facebook aswell.
I knew nothing about node.js a month ago so I'm kinda new to all this async stuff but I took some course to help myself. So far so good I can now manage users etc, (I've again some research to do with oauth).
My biggest problem is this "real-time" update on our server.
I mean I searched on the internet and saw this what we call polling (?), the idea to make request frequently to a server every X seconds.
So with a bit a sudo code this what I tought it would look like:
For each User
asynchronously watch for every update on Facebook and Twitter for
this User
So I did some research about performing request every each second and found about setInterval and setTimeout
const watchSocialMedia = setInterval(function(){
Users.forEach(user => {
User.watchAndPostAnyNewPost() //
}
}, 60000);
So I put some dummy data to illustrate.
Problem is I don't think It'll be done asynchronously ?
I mean the ideal is if I could put one time for each user a 'watcher' like saying
For each User
User.watchAndPostAnyNewPost()
where watchAndPostAnyNewPost() look like this
class User () {
...
const watchAndPostAnyNewPost = setInterval(function(){
fetchFacebook();
fetchTwitter();
}, 60000);
}
So each user have his own setInterval function running on him to check if he posted anything
Anyone can tell me if it's even possible ? :-)
Thanks a lot for reading me !!!
I want to use a linux device like a BananaPi with a socketcan-compatible can-controller to connect to a automotive can-bus and show its data in realtime on a webpage, which should be hosted on the Pi.
The data should be listed as hex-values and visualized via graphs (the different signals, for example the current speed).
After some research I discovered node-can and I could get managed to show the can-messages as a list on a webpage. But I noticed, that the messages come with a quite huge delay (~2 secs) when there is a huge busload (I sent can messages in a 1 ms period). The same delay occurs, if I use the following minimalistic example:
var can = require('socketcan');
var channel = can.createRawChannel("can1", true);
channel.addListener("onMessage", function(msg) { console.log(msg); } );
channel.start();
I am absolutely new in this topic but I think, that nodejs isn't the best choice to realize this project?
Are there any other (better) methods to realize such a system?
I could imagine something like a C-backend, for example based on candump (with this program no delay occurs at the same busload), and a frontend realized with javascript, html and css. But I have no idea how to get those different single programs together. Could you give me a keyword so I have a starting point for further research (websocket?!)?
I also thought about writing the can frames in a sql database and grab them from the database for the webpage-gui but I have no idea, if/how this works and if this is fast enough....
Thanks in advance!
I am building a webapp where user have a ranking based on their twitter activity and their activity on my website.
Therefore I'd like to update their rank every five minutes, pulling their latest activity from twitter and update it in my database. I was thinking of using something like this:
var minutes = 5, the_interval = minutes * 60 * 1000;
setInterval(function() {
// my update here
}, the_interval);
However, I have several questions about this code:
where should I save it to make sure it is run?
will it slow my program or is it a problem to pull data out of twitter every five minute? Should I use their streaming API instead?
Note: I am using mongoDB
I'd suggest that you create a scheduled task/chron job/etc. (depends on your host OS) to call a separate Node.JS application that performs the specific tasks you want to do periodically and then it would exit when complete. (Or you could use a ChildProcess potentially as well).
While Node.JS is async, there's no need, given the description you provided, to perform this work within the same application process that is serving a web application. In fact, as it sounds like "busy work", it would be best handled by a distinct process to avoid impacting directly any of your interactive web users.
The placement shouldn't really matter as Node is asynchronous.
On my website I have a list of all online users, updated in real-time by node.js (I'm using now.js)
The problem is, when a user navigates my site, they of course disconnect for a couple of seconds when the new page is loading. Which means they disappear from the list for all other clients, to pop back in just seconds later.
Is there any way to set a timeout on the disconnect function, e.g. if user has not reconnected in 30 seconds, remove from the list otherwise don't?
Or if there is a better way to accomplish this? Can someone please point me in the right direction :)
EDIT:
Came up with a working solution, if anyone would like to know. On server side I have this function
nowjs.on('disconnect', function() {
everyone.now.clientDisconnected();
});
which whenever a user disconnects calls this function on the client
now.clientDisconnected = function() {
setTimeout(function() { now.serverUpdateUsers(); }, 20000);
}
So instead of updating the users right away, we wait 20 seconds. By then the user should have finished loading the new page, and no difference will show for all other clients.
The serverUpdateUsers(); is the serverside function that gathers all user data and pushes it out to all clients.
I'm not exactly sure if you can modify Socket.IO's settings with now.js (which uses Socket.IO), but if you could (not sure, never used now.js) you should set the heartbeat interval to be bigger:
https://github.com/LearnBoost/Socket.IO/wiki/Configuring-Socket.IO
heartbeat interval defaults to 20 seconds