Setting timeout for vertx-eventbus.js - javascript

I'm currently working on a Vertx based application that is making use of vertx-eventbus.js as described here: http://vertx.io/docs/vertx-web/java/#_sockjs_event_bus_bridge
So the client side is using vertx-eventbus.js to send a message to server side which has SockJSHandler doing the 'bridge' to receive the message. The whole mechanism has been working fine for few months. Only very recently we now potentially need to have higher timeout limit for certain messages. If run right now, those messages always cause the following warning on the server side (and also caused the eventbus to attempt to return too early on client side with "undefined"):
Message reply handler timed out as no reply was received - it will be removed
My question is then how do you increase the timeout for the message sending in this scenario? It seems to be using the default 30 seconds timeout and I have looked everywhere (online searches Google, here at Stackoverflow, etc) with no luck. I know there is a way to set timeout when you are sending using Vertx on the backend but not when sending from vertx-eventbus.js.
Any input is very much appreciated. Let me know if there is anything else you need to better understand what I'm trying to achieve.
Thank you,
Tom

Related

How can I check in real time if a user is logged in?

I am building a simple support chat for my website using Ajax. I would like to check if the user that I am currently chatting with left the browser.
At the moment I have build in that feature by setting interval function at customer side that creates the file with name: userId.txt
In the admin area I have created an interval function that checks if userId.txt exists. If it exists, it deletes it. If the file is not recreated by the custom interval function - next time the admin function will find out that file is not there it mark customer with this userId as inactive.
Abstract representation:
customer -> interval Ajax function -> php [if no file - create a new file]
admin -> interval Ajax function -> php [if file exists - delete the file] -> return state to Ajax function and do something
I was wondering if there is any better way to implement this feature that you can think of?
My solution is to use the jquery ready and beforeunload methods to trigger an ajax post request that will notify when the user arrives and leaves.
This solution is "light" because it only logs twice per user.
support.html
<!DOCTYPE html>
<html>
<head>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.11.3/jquery.min.js"></script>
<script>
//log user that just arrived - Page loaded
$(document).ready(function() {
$.ajax({
type: 'POST',
url: 'log.php',
async:false,
data: {userlog:"userid arrived"}
});
});
//log user that is about to leave - window/tab will be closed.
$(window).bind('beforeunload', function(){
$.ajax({
type: 'POST',
url: 'log.php',
async:false,
data: {userlog:"userid left"}
});
});
</script>
</head>
<body>
<h2>Your support html code...</h2>
</body>
</html>
log.php
<?php
//code this script in a way that you get notified in real time
//in this case, I just log to a txt file
$userLog = $_POST['userlog'];
file_put_contents("userlog.txt", $userLog."\n", FILE_APPEND );
//userid arrived
//userid left
Notes:
1 - Tested on Chrome, FF and Opera. I don't have a mac so I couldn't test it on Safari but it should work too.
2 - I've tried the unload method but it wasn't as reliable as beforeunload.
3 - Setting async to false on the ajax request means that the statement you are calling has to complete before the next statement, this ensures that you'll get notified before the window/tab is closed.
#Gonzalon makes a good point but using a normal DB table or the filesystem for constantly updating user movement would be exhaustive to most hard disks. This would be a good reason for using shared memory functions in PHP.
You have to differentiate a bit between the original question "How do i check in real-time, if a user is logged in?" and "How can i make sure, if a user is still on the other side (in my chat)?".
For a "login system" i would suggest to work with PHP sessions.
For the "is user still there" question, i would suggest to update one field of the active session named LAST_ACTIVITY. It is necessary to write a timestamp with the last contact with the client into a store (database) and test whether that is older than X seconds.
I'm suggesting sessions, because you have not mentioned them in your question and it looks like you are creating the userID.txt file manually on each Ajax request, right? Thats not needed, unless working cookie and session-less is a development requirement.
Now, for the PHP sessions i would simply change the session handler (backend) to whatever scales for you and what makes requesting information easy.
By default PHP uses the session temp folder to create session files,
but you might change it, so that the underlying session handler becomes a mariadb database or memcache or rediska.
When the users sessions are stored into a database you can query them: "How many users are now logged in?", "Who is where?".
The answer for "How can I check in real time if a user is logged in?" is, when the user session is created and the user is successfully authenticated.
For real-time chat application there are a lot of technologies out there, from "php comet", "html5 eventsource" + "websockets" / "long polling" to "message queues", like RabbitMq/ActiveMq with publish/subscribe to specific channels.
If this is a simple or restricted environment, maybe a VPS, then you can still stick to your solution of intervalic Ajax requests. Each request might then update $_SESSION['LAST_ACTIVITY'] with a server-side timestamp. Referencing: https://stackoverflow.com/a/1270960/1163786
A modification to this idea would be to stop doing Ajax requests, when the mouse movement stops. If the user doesn't move the mouse on your page for say 10 minutes, you would stop updating the LAST_ACTIVITY timestamp. This would fix the problem of showing users who are idle as being online.
Another modification is to reduce the size of the "iam still here" REQUEST to the server by using small GET or HEADER requests. A short HEADER "ping" is often enough, instead of sending long messages or JSON via POST.
You might find a complete "How to create an Ajax Web Chat with PHP, jQuery" over here. They use a timeout of 15 seconds for the chat.
Part 1 http://tutorialzine.com/2010/10/ajax-web-chat-php-mysql/
Part 2 http://tutorialzine.com/2010/10/ajax-web-chat-css-jquery/
You can do it this way, but it'll be slow, inefficient, and probably highly insecure. Using a database would be a noticeable improvement, but even that wouldn't be particularly scalable, depending on how "real-time" you want this to be and how many conversations you want it to be able to handle simultaneously.
You'd be much better off using a NoSQL solution such as Redis for any actions that you'll need to run frequently (ie: "is user online" checks, storing short-term conversation updates, and checking for conversation updates at short intervals).
Then you'd use the database for more long-term tasks like storing user information and saving active conversations at regular intervals (maybe once per minute, for example).
Why Ajax and not Websockets? Surely a websocket would give you a considerably faster chat system, wouldn't require generating and checking a text file, would not involve a database lookup and you can tell instantly if the connection is dropped.
I would install the https://github.com/nrk/predis library. So at the time the user authenticates, It publishes a message to Redis server.
Then you can set-up a little node server on the back-end - something simple like:
var server = require('http').Server();
var io = require('socket.io')(server);
var Redis = require('ioredis');
var redis = new Redis();
var authenticatedUsers = [];
// Subscribe to the authenticatedUsers channel in Redis
redis.subscribe('authenticatedUsers');
// Logic for what to do when a message is received from Redis
redis.on('message', function(channel, message) {
authenticatedUsers.push(message);
io.emit('userAuthenticated', message);
});
// What happens when a client connects
io.on('connection', function(socket) {
console.log('connection', socket.id);
socket.on('disconnect', function(a) {
console.log('user disconnected', a);
});
});
server.listen(3000);
Far from complete, but something to get you started.
Alternatively, take a look at Firebase. https://www.firebase.com/ if you dont want to bother with the server-side
I would suggest using in built HTML5 session storage for this purpose. This is supported by all modern browsers so we will not face issues for the same.
This will help us to be efficient and quick to recognize if user is online. Whenever user moves mouse or presses keys update session storage with date and time. Check it periodically to see if it is empty or null and decide user left the site.
Depending on your resources you may opt for websockets or the previous method called long pool request. Both ensure a bidirectional communication between the server and the client. But they may be expensive on resources.
Here is an good tutorial on the websocket:
http://www.binarytides.com/websockets-php-tutorial/
I would use a callback that you (admin) can trigger. I use this technique in web app and mobile apps to (All this is set on the user side from the server):
Send a message to user (like: "behave or I ban you").
Update user status/location. (for events to know when attendants is arriving)
Terminate user connections (e.g. force log out if maintenance).
Set user report time (e.g. how often should the user report back)
The callback for the web app is usually in JavaScript, and you define when and how you want the user to call home. Think of it as a service channel.
Instead of creating and deleting files you can do the same thing with cookie benefits of using cookie are
You do not need to hit ajax request to create a file on server as cookies are accessible by javascript/jquery.
Cookies have an option to set the time interval so would automatically delete themselves after a time, so you will not need php script to delete that.
Cookies are accessible by php, so when ever you need to check if user is still active or not, you can simply check if the cookie exist
If it were aspnet I would say signalR... but for php perhaps you could look into Rachet it might help with a lot of what you are trying to accomplish as the messages could be pushed to the clients instead of client polling.
Imo, there is no need for setting up solutions with bidirectional communications. You only want to know if a user is still logged in or attached to the system. If I understand you right, you only need a communication from server to client. So you can try SSE (server sent events) for that. The link gives you an idea, how to implement this with PHP.
The idea is simple. The server knows if user is attached or not. He could send something like "hey, user xyz is still logged in" or "hey, user xzy seems not to be logged in any more" and the client only listens to that messages and can react to the messages (e.g. via JavaScript).
The advantage is: SSE is really good for realtime applications, because the server only has to send data and the client has only to listen, see also the specification for this.
If you really need bidirectional communications or can't go with the two dependencies mentioned in the specs, it's not the best decision to use SSE, of course.
Here is a late Update with a nice chat example (written in Java). Probably it's also good to get an idea how to implement this in PHP.

Return JS function as string from server and execute?

I'm trying to time limit a socket.io connection time on a node.js server. I asked a previous question as to whether this was possible without causing a huge overhead on the server and or blocking the main thread if we had say 1000 concurrent socket connections in various rooms, through something like:
socket.on('connection', function(params){
var maxTime = params.maxTime;
socket.join(params.roomId);
setTimeout(function{
socket.leave(params.roomId);
}, 180000)
});
The best case scenario would be handle this on the client side from a resources perspective but it isn't exactly secure to send the timeout/disconnection value as any lines of client side code that dealt with it could be easily manipulated and a knowing user could in effect prevent the disconnect event/functionality from being called.
Could I execute a function client-side sent as a string? Say:
setTimeout(function(){//disconnect},18000);
socket.emit('timeout_set', function(params){foo:bar});
Then handle appropriately on the server with a response knowing that the timeout has indeed been set:
socket.on('timeout_set', function(params){
socket.emit('proceed_with_stuff', {foo:bar});//includes critical info for proceeding
});
I'm thinking this depends on a few things:
Can you take a string from a server response and execute said string as JS?
Can a client still disrupt the setTimeout function without also triggering the socket.disconnect event?
Is this logic or anything similar possible?
Would the first scenario work on a node.js server given a number of concurrent connections?
Use Function constructor, see https://developer.mozilla.org/de/docs/Web/JavaScript/Reference/Global_Objects/Function

WebRTC: Can't set local description after creating an answer

I'm currently attempting to create a simple video chat service using WebRTC with Ajax for the signalling method.
As per the recommendation of another Stack Overflow user, in order to make sure I was understanding the flow of a standard WebRTC app properly, I first created a simple WebRTC video chat service in which I printed the created offer or answer and ICE candidates out to the screen, and manually copied and pasted that info into a text area in the other client window to process everything. Upon doing that, I was able to successfully get both videos to pop up.
After getting that to work properly, I decided to try and use Ajax as the signalling method. However, I can't seem to get it to work now.
In my current implementation, every time offer/answer or ICE candidate info is created, I instantly create a new Ajax object, which is used to add that info (after the JSON.stringify method has been executed on it) to a DB table. Both clients are constantly polling that DB table, searching for new info from the other client.
I've been echoing a lot of information out to the console, and as far as I can tell, a valid offer is always sent from one client to another, but upon receiving that offer, successfully setting it as the remote description, and creating an answer, any attempts I make to set the local description of the "answerer" fails.
Is there any particular reason why this might happen? Here's a snippet of my code:
var i,
len;
for (i = 0, len = responseData.length; i < len; i += 1) {
message = JSON.parse(responseData[i]);
if (message.type === 'offer') {
makeAnswer(message);
}
// Code omitted,
}
...
makeAnswer = function (offer) {
pc.setRemoteDescription(new RTCSessionDescription(offer), function () {
pc.createAnswer(function (desc) {
// An answer is always properly generated here.
pc.setLocalDescription(desc, function () {
// This success callback function is never executed.
setPayload(JSON.stringify(pc.localDescription));
}, function () {
// I always end up here.
});
});
});
};
In essence, I loop through any data retrieved from the DB (sometimes there's both an offer and lots of candidate info that's gathered all at once), and if the type property of a message is 'offer', I call the makeAnswer function, and from there, I set the remote description to the received offer, create an answer, and try to set the answer to the local description, but it always fails at that last step.
If anyone can offer any advice as to why this might be happening, I would be very appreciative.
Thank you very much.
Well, I figured out the problem. It turns out that I wasn't encoding the SDP and ICE info before sending it to a PHP script via Ajax. As a result, any plus signs (+) in the SDP/ICE info were being turned into spaces, thus causing the strings to differ between the local and remote clients and not work.
I've always used encodeURIComponent on GET requests with Ajax, but I never knew you had to use that function with POST requests as well. That's good to know.
Anyway, after I started using the encodeURIComponent function with the posted data, and then fixed my logic up a bit so that ICE candidates are never set until after both local and remote descriptions are set, it started working like a charm every time.
That's the good news. The bad news is that everything was working fine on my local host, but as soon as I ported the exact same code over to my web-hosted server, even though the console was reporting that the offer/answer and ICE info were all properly being received and set, the remote video isn't popping up.
Sigh. One more hurdle to cross before I can be done with this.
Anyway, just to let everyone know, the key is to use encodeURIComponent before sending the SDP/ICE info to a server-side script, so that the string received on the other end is exactly the same.

Android HTTP GET cookie / javascript issue?

I wrote an Android app that should 'connect' to a (private) forum using HTTP GET (and sometimes POST) requests. The basic idea is as such:
Login page where users submit their credentials. Login is performed by doing a HTTP POST (tried GET too, same result) to the Login page of the forum, with their username and password as the parameters. The request should return some cookies that I store in a BasicCookieStore.
Every page of the forum they want to visit is retrieved using HTTP GET. I parse the HTML source that I obtain and show them only the relevant info. In order to authenticate the users, the same BasicCookieStore that I used for login (step 1) is set as the cookiestore for the HttpClient.
This method has been working all the time during my testing, and has worked for my beta testers too. Now that I released the app, it became apparent that many users were having issues, especially on mobile connections (Wifi seems to be no problem).
By logging the HTML source that was returned in all the HTTP GET requests, I have a strong suspicion that the actual login works fine, but somehow the cookies don't get returned or stored or something in that direction. The problem is that the HTML source of the first page they will receive should be the list of forums. In the case of users with problems however, they get served a page that basically reads "You must enable Javascript to view this page".
The strange thing is, I don't receive that page when testing, nor do many of my users. Even worse: some users are now reporting it worked fine for them for days or weeks, and has now stopped working. Others have the exact opposite: not working for days, suddenly working now. One user has reported he was in Greece for 2 weeks, where it worked flawlessly, then he got back to Germany, and it stopped working again.
There seems to be a random component at play here.
I have tried various things, mostly with the way I do the HTTP GET requests. I started out using the normal DefaultHttpClient, with various settings, such as this:
HttpClient httpClient = new DefaultHttpClient();
// Define parameters
HttpParams httpParams = httpClient.getParams();
HttpConnectionParams.setConnectionTimeout(httpParams, TIMEOUT);
HttpConnectionParams.setSoTimeout(httpParams, TIMEOUT);
HttpProtocolParams.setVersion(httpParams, HttpVersion.HTTP_1_1);
// Set cookiestore (getCookieStore returns the same cookiestore)
HttpContext localContext = new BasicHttpContext();
localContext.setAttribute(ClientContext.COOKIE_STORE, getCookieStore());
HttpGet http = new HttpGet(url);
http.addHeader("Accept", ACCEPT_STRING);
http.addHeader("Content-Type", "application/x-www-form-urlencoded; charset=utf-8");
// Execute
HttpResponse response = httpClient.execute(http, localContext);
//... Process result (omitted)
Now I have switched to using AndroidHttpClient instead, with the rest of the code basically unchanged, and seem to get the same result.
I have also tried using the AsyncHttpClient library, which works quite differently, but once again the same result. I tried using its PersistentCookieStore as well, and you guessed it - same result.
I am clueless at this point. Am I looking in the wrong direction? The fact that a website would respond with "you need to enable Javascript" for some users but not for all seems to indicate an issue with cookies. I don't know how a website determines if javascript is enabled, but surely with a HTTP GET request there is no javascript at play. So why do I (and many other users) get to the page without any problems, while others get the 'no javascript' message? The only reason I can think of is cookies, but I have no clue what the problem exactly is.
Any help would be much appreciated!
I doubt the problem is cookies. More likely is a network configuration problem.
For example, your user might have connected to a wifi hotspot with a captive portal page (which uses javascript to make you sign in before you can use the hotspot). In this case they should first open the browser, try to browse to (e.g.) http://google.com, get redirected, sign in, and then launch your app.
Or, your user might be connecting through a proxy. Many mobile carriers around the world will proxy their users' HTTP connections, sometimes doing horrible things to the content. Switching to HTTPS might help with that.

How would you create an auto-updating newsfeed without a reload?

How would I go around creating an auto-updating newsfeed? I was going to use NodeJS, but someone told me that wouldn't work when I got into the thousands of users. Right now, I have it so that you can post text to the newsfeed, and it will save into a mysql database. Then, whenever you load the page, it will display all the posts from that database. The problem with this is that you have to reload the page everytime there is an update. I was going to use this to tell the nodejs server someone posted an update...
index.html
function sendPost(name,cont) {
socket.emit("newPost", name, cont);
}
app.js
socket.on("newPost", function (name,cont) {
/* Adding the post to a database
* Then calling an event to say a new post was created
* and emit a new signal with the new data */
});
But that won't work for a ton of people. Does anyone have any suggestions for where I should start, the api's and/or programs I would need to use?
You're on the right track. Build a route on your Node webserver that will cause it to fetch a newspost and broadcast to all connected clients. Then, just fire the request to Node.
On the Node-to-client front, you'll need to learn how to do long polling. It's rather easy - you let a client connect and do not end the response until a message goes through to it. You handle this through event handlers (Postal.JS is worth picking up for this).
The AJAX part is straightforward. $.get("your/node/url").then(function(d) { }); works out of the box. When it comes back (either success or failure), relaunch it. Set its timeout to 60 seconds or so, and end the response on the node front the moment one event targetted it.
This is how most sites do it. The problem with websockets is that, right now, they're a bit of a black sheep due to old IE versions not supporting them. Consider long polling instead if you can afford it.
(Psst. Whoever told you that Node wouldn't work in the thousands of users is talking through their asses. If anything, Node is more adapted to large concurrency than PHP due to the fact that a connection on Node takes almost nothing to keep alive due to the event-driven nature of Node. Don't listen to naysayers.)

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