OK, here's the situation - simple and clear :
On Page A : We perform an ajax request (let's say to intermediate.php) which initiates a background process - let's say back.php
interm.php returns
back.php keeps working until it finishes, while updating its progress in a db.
So, how could Page A get notified that back.php has finished?
(I've thought e.g. of firing an ajax request every 1-2 secs to a script checking the db for back.php's progress, but that seems pretty weird and definitely not efficient...)
Any ideas?
You could do a long-polling or short-polling technique which is quite common and not so weird. It does make a lot of unnecessary requests, but it's the simplest and most supported method out there.
The second method would be using web sockets. Now web sockets through html5 are not generally supported as of now, but an alternative would be to use a library that takes care of fallbacks to other methods such as flash, or even long-polling if your browser / device doesn't support a previous method. A really good library for real-time communication would be Socket.IO. It allows many different implementations of real-time or close to real-time, it also allows you to choose which method of communication you want to use. Some cloud based web services such as Paas don't widely support web sockets. Libraries will go around this by letting you choose or force a specific method of communication: Web Sockets, Flash Sockets, Long-Polling, etc..
But since your using php, you could try this: https://github.com/lemmingzshadow/php-websocket
http://www.htmlgoodies.com/html5/other/create-a-bi-directional-connection-to-a-php-server-using-html5-websockets.html#fbid=8Pw-Juo8eHG
Slightly different approach
http://www.gamedev.net/topic/613642-socketio-php-mysql/
http://devzone.zend.com/209/writing-socket-servers-in-php/
socket.io + php + is this a realistic solution at this point in time
Though as mentioned on some of these sites, using websockets with php is not as straight forward as node.js or twisted python. But nonetheless it's achievable and does work at some degree. I found that having a node.js backend to do the real-time stuff is a lot easier then trying to force a technology that is not meant to be worked in that way.
What you're basically looking for is Comet. Here's a good thread on it:
Using comet with PHP?
Related
I have been in search of making live websites by using PHP. (COMET) I have been searching for a very long time already. (around a month) I have even checked some PHP chat scripts and used on my webserver, but I had some problems on most of them. (will be explained)
So far, most of the people tells the same thing: PHP isn't the best language could be used with COMET. The chat/comet examples are hacky at best.
I am asking this because, I want to have some features on my websites, like allow logged in people to chat with each other. That is where I need an alive connection to PHP pages. I am also planning on making a browser based game, and an alive connection will still be a must!
AJAX was a rare thing 2 years ago, shined with Facebook. Now pretty much everyone uses it, and it became a standard on web development. Now, the COMET based websites are growing. Youtube, Google+, Facebook, EA's Battlelog and such. I believe I should learn how to use it.
Okay, here are my questions. (Some of the information at below are the ones I gathered while searching on Google. Not sure if they're correct or not.)
Some languages like Python have special web servers designed for this job. I believe one of them is called Tornado Web Server. Developed and configured to simulate thousands of alive connections. I believe there is no such option in Appserv, but some people told NGINX can handle it with a decent configuration. Is it true? What configurations should be made? Is there any PHP web servers for this job?
Some of the most suggested things are:
a. Using APE.
b. Using Socket.IO
c. Node.js
Is there any way we can use them with PHP? Which one is the most promising? Could you give some guidance on them? Is there anything else than these?
I have used a comet chat script. Basically, you kept querying database and output the result with flush() to browser by sleeping it with usleep() in a loop. (This one became hard to understand so I will provide a quick code)
while(true)
{
// query database
// output the result
// flush the browser
// sleep for few seconds to lower cpu load
}
usleep() function basically destroyed my web server on Windows based operating systems. Is it normal to rely on usleep() on comet applications which runs on windows based OS? I mean, is there even a way to "sleep" PHP scripts? No matter what I do, CPU load goes to %100 on both WIN and UNIX servers.
Is PHP "really" that weak on this area? Should I give up with PHP and focus on other languages? If so, which language would you suggest? (That language should be promising. For example, there is no much use of AS3 after HTML5 addition, and AS3 is more likely to die soon while JS shines.)
What is WebSync? Can it be used with PHP?
Please bear in mind that I need to use COMET to make following applications:
A chat script, where logged in players will be able to chat eachother.
A browser based game. I already use JSON/AJAX and things like that when coding, but to receive opponents steps, I should pull the data, so an alive connection is needed. (Don't imagine advanced games, I am speaking about games like chess at best.)
I would appreciate if you can give me a short guidance. After all, I have been getting confused day by day since there are SO MANY random articles on internet. People even call setInterval() as COMET, so it is a complete mess.
There needs to be some clarification here. What you're looking for is not language specific per se. If you wanted to achieve the comet functionality with PHP you'd be relying on the Web Server (e.g Apache) to do the HTTP streaming. Also you need to understand that this is not supported in HTTP versions prior to HTTP/1.1. With that said, if you want to have a non-blocking event based web server, you're better off looking at Tornado and Node as suggested.
Comet is a programming technique that enables web servers to send data to the client without having any need for the client to request it This technique will produce more responsive applications than classic AJAX The user must create a request (for example by clicking on a link) or a periodic AJAX request must happen in order to get new data fro the server.
but it's create lots of traffic on your web server. If you want to build chat application in PHP use pusher which is a third party service and easy to use.
here is a link for pusher https://pusher.com/tutorials/realtime_chat_widget
the second suggestion is use ratchet for creating a chat application.
here is link for ratchet http://socketo.me/docs/hello-world
i hope it will help you
How to implement a real fast web chat with PHP?
Has anybody ever wonder why Facebook chat is just so really really fast? even in IE without WebSocket.
Isn't the only way is to setInterval in JS to check for new messages? But I feel it (Facebook chat box) like having instant reaction.
How to implement such great thing with PHP?
The instantaneous chat you're describing is generally acheived by a something called "Long Polling" or, if we're talking about AJAX, "Comet" (Wikipedia talks about it). Polling tends to strain Apache servers, but there are some specialized servers to deal with it like APE. I'm not sure but I think you can do the same with NodeJS and NGINX handles the stress pretty well.
Here's an article here about how to implement a long polling chat with PHP jQuery and AJAX.
Best of luck, and I hope it helped!
I agree with #joseph-szymborski although it would make sense to start looking at WebSocket solutions which fallback to WebSockets via Flash and/or long-polling.
Here are some relevant SO questions:
How to implement facebook like notification on cakephp? - PHP/jQuery
ajax Push system - PHP/Ajax
Apache with Comet Support - the question itself is very good.
PHP Jquery: chat system, what is the Ideal framework for this? - relevant to your question.
If you want to work with PHP or are on shared hosting then I'd recommend looking at a hosted realtime web solution.
You might want to consider Node.js to serve the clients in 'real time' since Long polling with PHP/AJAX may cause strain on your server.
But the implementation itself is an uphill task. Just saying.
Long polling with PHP/AJAX may cause strain on your server.
My typical theoretical implementation of the same:
Create a Node.js server to query a database.
Send variables and/or session data from php to Node js using cURL.
Parse the url in your Node.js server and use the variables to check
for changes in database.
Emit new data if changes occur and send to client.
I'd like to develop a near real time web based chat system. Any suggestions on how to implement this via jQuery, any gotchas to look out for, and what is this Comet thing I keep reading about?
Ideally, I'd like to support up to about 5,000 concurrent chatters.
Comet, also known as Ajax Push, is often refered as "Reverse AJAX". Instead of pulling the information from the server in regular intervals, the data is pushed from the server to the browser when it is needed. That requires an open connection, for which there are several implementations.
I recommend that you use APE. Here is a demo: http://www.ape-project.org/demos/1/ape-real-time-chat.html
Advantage: It will be very responsive
and real-time.
Disadvantage: You need
to setup the APE server on your
webserver machine.
Comet is a "push" tecnology, created to avoiding the client (javascript code) to continously poll the server. This could cause bandwith problem, because you have to create (maybe) a new TCP connection, then contact the http server, he runs some server-side logic and then sends a response to the client. With comet, if the server decide that you should recive some information (e.g., new chat message) he directly send it to the client.
There are several different implementation, you can have a start here.
the simplest implementation tecnique is the hidden iframe, but I'd raccomend the long polling wich is much more controllable.
One more thing, thake a look at HTML5 websokets, wich could be an interesting solution to your problem (not very compatible with current browser, anyway)
Check out Node.js and nowjs for node.js. Node.js helps you build very efficient servers using server side JavaScript and nowjs is a library that allows you to build real time web apps. There is even a example screen cast that puts together a basic chat application in 12 lines of code.
You could also checkout Socket.io which is another node library thats helps you build real time apps by abstracting away different transport mechanisms and giving you a unified interface to code against (supports WebSockets, Flash Sockets, AJAX long polling, JSONP Polling and Forever IFrames).
I realize you tagged your question PHP but if you are seriously considering writing a scalable system with the least amount of effort (relatively speaking) then learning Node.js is worth your time (and the learning curve is not thats steep since you probably already know JS).
We need to create a web-based frontend for displaying some data. The problem is that the data needs to be updated about once a second.
For me as a web-developer the obvious solution is AJAX.
Unfortunately, one of the purposes of this web frontend is to be displayed inside of embedded browser window which is expected to run constantly for months or even years. That's it, months of work with no restart / refresh.
During testing we ran a proof of concept interface (which requested a simple set of data each 1,5s) in Safari for over a month. During this period of time, the memory usage of Safari raised from ~30 MB to over 100MB.
Thus we're afraid of stability of such a solution.
I'm wondering if you could recommend us any other technique for this task, possibly with less overhead (when requesting simple sets of data - as in our case - I'm afraid the HTTP headers are very significant part of data)
I would suggest looking into node.js and the now.js plugging, which allows for realtime updates via websockets. It even has support for older browsers, so if the browser does not support websockets, it will do a fall over to either a comet server implementation, AJAX or an iframe.
It's extremely easy to setup on a linux environment, and there's ample documentation to get you started.
It works with javascript and runs on the Google V8 javascript engine, so if you've ever worked with OOP Javascript, you should be able to pick it up relatively easy.
LINKS:
http://nodejs.org/
http://nowjs.com/
How about Adobe AIR as front-end? You can use Flash/FLEX inside which have decent garbage collectors so long running shoudn't be a problem. AIR also allows to write in XHTML and JavaScript so it could be a good option if you're only familiar with those technologies
PHP is not a good choice for this kind of requests. Comet seems to be a good way to receive data from server. You can use for example excellent Tornado (Python) as backend.
ActionScript allows to use TCP sockets so you can write your own protocol for even better performance and use BOOST Asio (C++) or Netty (Java) as scalable backend
Maybe websocket ? Instead of making an AJAX request each X seconds, the server push new data as they comes.
My personal faverite is php4+, mysql, apache or lightpd webserver.
Tough I also suggest Python.
I specialize in what you are mentioning, with that said, will you be actually looking at the screen? If not you should request the page using an http socket or via a wget cronjob on a linux box.
Yes the http header is very important, if you try to strip them out the webserver will issue a "Server - Bad Request" Error.
Let me know what you decide, I have a lot to share :)
I suspect that the problem is not AJAX per se, but using a browser an sich: I don't think any where made with constant running in mind, and I'm assuming that all (re)loading processes will become some form of extra memory in the end.
I think you would be best off to consume your data trough something simple you design yourself. You can obviously produce it on the same spot (server, requestable via HTTP or whatever you like most), but you do not need a complete webbrowser if your goal is first "a couple of years uptime".
Is there a real solution for COMET AND PHP combination? Basically, I've come to a point that I need to update a user home page periodically whenever there is new data in the database. As far as I understand, I need to open a persistent connection between my server and my clients browsers to update the contents of their home page as soon as new info. available without dedicating a lot of resources but I had no luck finding anything clear about this issue. I read many articles suggests that PHP is not a good language to implement COMET. My web application is completely programmed in PHP and I don't want to learn another language but if I'm forced to, Would you suggest a good language to start with? Do you think that I can program an interface just to handle this issue?
Thanks in advance.
The times I've heard people say that PHP was not well suited for COMET (like you said yourself) was because of the way webservers and PHP work -- mostly, because there is one process per page, which means if you want 200 users connected to your server, you'll need 200 processes (which can quickly become a problem for a couple of hundred more users).
Maybe a solution to that problem would be to use nginx_http_push_module ?
I've not tried it (yet ?), but it might be just what we need...
I was working on a school project and ran into the exact same problem. Because each PHP process has so much memory overhead, it's impossible to support to many connections per box. It was at this point I decided to switch to using BOSH and XMPP. This is a rather new "wave" of technology but there is already quite a few libraries to help you on your way. I would suggest using Strophe and XMPPHP. Then your clients can connect to a BOSH server (I'm using Openfire) and that can scale to thousands of active connections per server.
You don't have to learn a new language to implement such a feature.
For example, you could use Quercus (Java implementation of PHP) and implement a server Comet application using the JVMs memory management model.
There are solutions you need:
almost COMET solution (uses php and one file written with perl):
http://translate.google.com/translate?js=y&prev=_t&hl=ru&ie=UTF-8&layout=1&eotf=1&u=http://dklab.ru/lib/dklab_multiplexor/&sl=ru&tl=en
exact COMET solution in php (this is what you want, I think):
http://translate.google.com/translate?hl=ru&sl=ru&tl=en&u=http://dklab.ru/lib/dklab_realplexor/
You would first need to understand what is a comet application like. The concept involved in building a comet application are explained at wiki at Comet (programming)
What you need to understand is that you can use any programming language to build a comet application as long as it follows the concepts explained at wiki
1.Ajax with long polling
2.Streaming
You can check some sample code at Simple “Long Polling” example code
Now coming to the problems -
1.You use ajax long polling then the browser(ajax request) would keep polling the server for data. This may eat up memory on the server or slow down the browser after some time.
Few Suggestions
JQuery PeriodicalUpdater (AJAX long polling/server polling)
Handling Long Polling
RobertFischer / JQuery-PeriodicalUpdater
What you need to check to implement this -
a) How often do you expect data to be updated on the server.
b) How much time the server side script would run to check, fetch and process data before sending it to the client side.
2.You can implement streaming by using the following -
How to implement COMET with PHP
Lightstreamer Dojo
Dojo Charting + Lightstreamer Comet Demo
Demo
Ajax Push Engine or The APE Project
What you need to check for this -
a) Will your hosting provider allow you to install these on hosting servers
b) Your RAM and Bandwidth utilization (You will need a dedicated server with package that gives you lots of RAM and Bandwidth)
It depends on what and how your requirements are. You will have to analyze and approach.
If what you are implementing is a small application you can go for Ajax Long polling given the fact that you analyzed and handled the negatives of this approach.
If you have a large application you can go for steaming.
Ajax with long polling is a easy solution, there are plugins in jquery and any other major js framework to help you do this.
Node.js seems like a pretty sweet solution for stuff like this. (Still a little gamey for production but cool all the same). PHP is a horrible environment for stuff like this, you have to change the way the server interacts with requests because you are no longer immediately responding. Python has a handful of servers like Twisted that are great for this because they let you be the server. No matter what language you write it in you've got to alter the typical request/response model. (Glassfish's Grizzly Comet server does this for Java as an example)
You should try Dmitry Koterov's Realplexor, which is a comet server, that provides Javascript and PHP APIs.
Readme.txt in english is provided in the package.