After searching the web for a good Comet and also and asking you guys what my best option is, I've chose to go with Orbited. The problem is if you need a good documentation about Comet you won't find. I've installed Orbited and It seems It works just fine.
Basically, I want to constantly check a database and see if there is a new data. If there is, I want to push it to my clients and update their home page but I can't find any good and clear doc explaining how constantly check the database and push the new info to Orbited and then to the clients. Have you guys implemented that?
Also, how many users can Orbited handle?
Any ideas?
You could add a database trigger that sends messages to your message queue when the database got changed. This is also suggested here. Or, if it is only your app talking to the database, you could handle this from within the app via a Subject/Observer pattern, notifying the queue whenever someone called an action changing something in the DB.
I don't know how good or bad Orbited scales.
Have a reference table that keeps track of the last updated time of the source table. Create a update/delete/insert trigger for the source table that updates the time in the reference table.
Your comet script should keep checking the reference table for any change in the time. If the change is noticed, you can read the updated source table and push the data to your client's home page. Checking the reference table in a loop is faster because the MySQL will serve the results from its cache if nothing has changed.
And sorry, I don't know much about Orbited.
I would use the STOMP protocol with Orbited to communicate and push data to clients. Just find a good STOMP client with PHP and get started.
Here is an example of a use case with STOMP, although the server side is written in Ruby:
http://fuglyatblogging.wordpress.com/2008/10/
I don't know if PHP with Apache (if that's what you are using) is the best suite for monitoring database changes. Read this article, under the section title "Orbited Server", for an explanation: http://thingsilearned.com/2009/06/09/starting-out-with-comet-orbited-part-1/
EDIT: If you want to go the route with PHP through a web server, you need to make one, and one only, request to a script that starts the monitoring and pushes out changes. And if that script times out or fails, you need to start a new one. A bit fugly :) A nicer, cleaner way would be, for example, to use twisted with python to start a monitoring process, completely separated from the web-server.
Related
I am a programmer at an internet marketing company that primaraly makes tools. These tools have certian requirements:
They run in a browser and must work in all of them.
The user either uploads something (.csv) to process or they provide a URL and API calls are made to retrieve information about it.
They are moving around THOUSANDS of lines of data (think large databases). These tools literally run for hours, usually over night.
The user must be able to watch live as their information is processed and is presented to them.
Currently we are writing in PHP, MySQL and Ajax.
My question is how do I process LARGE quantities of data and provide a user experience as the tool is running. Currently I use a custom queue system that sends ajax calls and inserts rows into tables or data into divs.
This method is a huge pain in the ass and couldnt possibly be the correct method. Should I be using a templating system or is there a better way to refresh chunks of the page with A LOT of data. And I really mean a lot of data because we come close to maxing out PHP memory and is something we are always on the look for.
Also I would love to make it so these tools could run on the server by themselves. I mean upload a .csv and close the browser window and then have an email sent to the user when the tool is done.
Does anyone have any methods (programming standards) for me that are better than using .ajax calls? Thank you.
I wanted to update with some notes incase anyone has the same question. I am looking into the following to see which is the best solution:
SlickGrid / DataTables
GearMan
Web Socket
Ratchet
Node.js
These are in no particular order and the one I choose will be based on what works for my issue and what can be used by the rest of my department. I will update when I pick the golden framework.
First of all, you cannot handle big data via Ajax. To make users able to watch the processes live you can do this using web sockets. As you are experienced in PHP, I can suggest you Ratchet which is quite new.
On the other hand, to make calculations and store big data I would use NoSQL instead of MySQL
Since you're kind of pinched for time already, migrating to Node.js may not be time sensitive. It'll also help with the question of notifying users of when the results are ready as it can do browser notification push without polling. As it makes use of Javascript you might find some of your client-side code is reusable.
I think you can run what you need in the background with some kind of Queue manager. I use something similar with CakePHP and it lets me run time intensive processes in the background asynchronously, so the browser does not need to be open.
Another plus side for this is that it's scalable, as it's easy to increase the number of queue workers running.
Basically with PHP, you just need a cron job that runs every once in a while that starts a worker that checks a Queue database for pending tasks. If none are found it keeps running in a loop until one shows up.
I am a PHP developer and the title basically says it all. However I was hoping on some more in-depth information as I am starting to get confused about how the flow for the project I work on should go.
For an (web) application I need to implement a feature like Facebook does it with notifying users about replies/comments and instantly showing these.
I figured I could use long-polling with ajax requests but this does not seem to be a nice solution as the notifications never really are instant and it is resource heavy.
So I should use some form of sockets if I understand correctly, and Node.Js would be a good choice. So based on the last assumption I now get confused about the work flow.
I thought about two possible solutions:
1) It seems to me, that if I would use Node.Js I could skip using PHP at all and base the application on Node.js only.
2) Or I could use PHP as a base and only use Node.js for notifying users and instantly showing messages but saving the data using PHP and Mysql.
These two possibilities confuse me and I can't make up my mind about what would be the "best" and cleanest way.
I do not have much experience in Node.js, played with it for a while. But managing and saving data seems to be hard in Node.js so that is why I came up with option 2.
I know Facebook is build on PHP so I am assuming that they save the data via PHP and notify / instantly show replies and comments via Node.
Could someone help me out on this?
Thanks in advance!
EDIT:
I just noticed, Stackoverflow does something similar. I get a notification in the upper left, and below my question a box with "new answer to this question". I am really interested in the technologie(s) used.
Well you could use node.js for the notifications and PHP for your app.
By googling I found this about real-time-notifications.
You could also just use node.js with socket.io, but this means that you have to learn new technologies as you mention that you have no experience with node.
I haven't used it but you could check this project, for websockets in PHP.
When you have an update that you want to notify users you can use the publish subscriber pattern to notify the intrested in this update.
Take a look in Gearman too.
Personally, I've built a notification system using the pubsub mechanism of redis, with node.js+socket.io. Everytime that there is an update on a record then there is a publish on the appropriate channel. If the channel has listeners then they will be notified. I also store the last 20 notifications in a Redis list.
The appplication is built in PHP. The notification system is built in node.js. They are different applications that see the same data. The communication occurs via redis. For example in the Facebook context:
1) A user updates his status.
2) PHP stores this to the database and Redis
3) Redis knows that this update must publish to the status channel of the specific user and it does.
4) All the friends of the specific user are listening to his status channel (here comes node.js)
5) Node.js pushes the notification in the browser with socket.io
As for facebook, I have read in an article that is using long polling for supporting older browsers. Not sure for this though, needs citation...
AFAIK It would be via two simple methods :
First one that could be very simple is adding a Boolean column to each record that determines if it has been notified or not.
The second method is creating a table to insert all notifications.
However, I'm not sure if there are alternative methods for better performance, But first method is what I do commonly myself. But I think Facebook is using 2nd method, because it has to notify each one to a lot of users.
Your question maybe dublicate of:
Facebook like notifications tracking (DB Design)
Database design to store notifications to users
You could use Server Side Events it involves a bit of JavaScript but nothing overly complicated I think.
The main bulk of this method is PHP though, so you would just use the PHP to query your DB for notifications and SSE will push them to the user.
It does have some limitations though, most notably it's not supported by IE (huge surprise) thought i'd mention it anyway to let you know of other possibilities.
Hope this helps
Is there any way you can push data to a page rather than checking for it periodically?
Obviously you can check for it periodically with ajax, but is there any way you can force the page to reload when a php script is executed?
Theoretically you can improve an ajax request's speed by having a table just for when the ajax function is supposed to execute (update a value in the table when the ajax function should retrieve new data from the database) but this still requires a sizable amount of memory and a mysql connection as well as still some waiting time while the query executes even when there isn't an update/you don't want to execute the ajax function that retrieves database data.
Is there any way to either make this even more efficient than querying a database and checking the table that stores the 'if updated' data OR tell the ajax function to execute from another page?
I guess node.js or HTML5 webSocket could be a viable solution as well?
Or you could store 'if updated' data in a text file? Any suggestions are welcome.
You're basically talking about notifying the client (i.e. browser) of server-side events. It really comes down to two things:
What web server are you using? (are you limited to a particular language?)
What browsers do you need to support?
Your best option is using WebSockets to do the job, anything beyond using web-sockets is a hack. Still, many "hacks" work just fine, I suggest you try Comet or AJAX long-polling.
There's a project called Atmosphere (and many more) that provide you with a solution suited towards the web server you are using and then will automatically pick the best option depending on the user's browser.
If you aren't limited by browsers and can pick your web stack then I suggest using SocketIO + nodejs. It's just my preference right now, WebSockets is still in it's infancy and things are going to get interesting once it starts to develop more. Sometimes my entire application isn't suited for nodejs, so I'll just offload the data operation to it alone.
Good luck.
Another possibility, if you can store the data in a simple format in a file, you update a file with the data and use the web server to check its timestamp.
Then the browser can poll, making HEAD requests, which will check the update times on the file to see if it needs an updated copy.
This avoids making a DB call for anything that doesn't change the data, but at the expense of keeping file system copies of important resources. It might be a good trade-off, though, if you can do this for active data, and roll them off after some time. You will need to ensure that you manage to change this on any call that updates the data.
It shares the synchronization risks of any systems with multiple copies of the same data, but it might be worth investigating if the enhanced responsiveness is worth the risks.
There was once a technology called "server push" that kept a Web server process sitting there waiting for more output from your script and forwarding it on to the client when it appeared. This was the hot new technology of 1995 and, while you can probably still do it, nobody does because it's a freakishly terrible idea.
So yeah, you can, but when you get there you'll most likely wish you hadn't.
Well you can (or will) with HTML5 Sockets.
This page has some great info about this technology:
http://www.html5rocks.com/en/tutorials/websockets/basics/
Assume that I have a simple VPS setup with LAMP (so with PHP and MySQL on the same server and no other strings attached). And assume that I want to make a self-written ajax chat client on my website.
Obviously, each participant in the conversation would have to listen constantly for new things being said. Since it is very well possible that two or more participants say something in the very same second (and refreshing more than once per second would likely cause insane system load), it seems to me that I would need to store for each participant a list of things that happened since the last refresh.
Which would be the "best" way to do this (in terms of system load)? In the following, an "event" just 'any participant saying anything in the chat'. Clearly, this could be used for a more general as well.
(A) Use MySQL, connecting to the db every second and asking for events WHERE participant_id = $participant_id? (and then deleting all of these so they're only fetched once)
(B) Create a file $participant_id.php and append the events to it (in PHP format so that it can be included, and then empty or delete the file at the next refresh?
(C) Does anyone know any other useful alternatives?
An alternative would be to use a socket connection. Each person connected to the socket server daemon would be able to send a message to the daemon, the daemon would then send the message out to all or a partial list of subscribers which makes chat instantaneous with no need to save the data at all.
A good way to create socket connections from a client is socket IO. See below.
http://socket.io/
A good technology to use for creating a socket server daemon is node.js. This is a server side event driven javascript based library. Very efficient for things like this. See below.
http://nodejs.org/
On both A and B you are still effectively polling. You will either poll MySQL which really isn't too bad, or you can get notified on select() of a file change BUT you will still need to parse to see if the new data is the right stuff on the file-side.
For conceptual and support ease-of-use, it is really hard to beat a database as you won't have to worry about locking semantics. Debugging and message tracking are clean in this structure.
I however recommend you investigate the msg_send() and msg_receive() (of PHP) functions to put this data into an underlying message queue. Your problem seems to be a message queueing problem that should be solved by that mechanism.
Does anyone know any other useful alternatives?
If you search simple solutions on PHP, I can offer 2 ways:
Cache
It mean that you keep MySQL for store data, but install APC (this solution is simplest and fastest for small servers and applications) or Memcached (better for using width several servers). For each read-request you check APC/Memcached for you data and ask MySQL only if your cache is removed or updated. And on each write-request you inserting data in MySQL and update cache.
Other DB
In this case you change MySQL for one of memory-base DB (for example MongoDB). And you may not afraid hard disk usage.
I've written a php file that changes a MySql table entry when it receives an http post. I would also like the php file to send out a notification to the table entry's owner. This idea is similar to a chat room or instant messengering program. I've looked at php chat scripts but I really need something that has a very simple interface that is customizable. Can anyone point me in the right direction?
So you want to synchronize a set of clients, do you?
If so, look at the Long Polling technique. It's quite simple: The client opens a connection but the server does not respond until data is updated.
On the downside this won't work well with PHP. You will need to sleep() several connections, therefore blocking PHP processes.
If you have the possibility I would recommend using node.js to do stuff like that. Long Polling Chats are quire simple to implement using node ;)
I would use a named look for event triggerning and a jabber bot (extensions exist for several languages).
http://www.xaprb.com/blog/2007/08/29/how-to-notify-event-listeners-in-mysql/