Efficient reloading data / pushing data from server to client
I'm looking for the 'way to go' (i.e. the most efficient, most used, general accepted way) when it comes to the reloading of data from a web server to a front end. In the end application, I will have several output fields where data has to be written to, for example like this:
The data streams will be different from each other in the end application. The lines will have to be reloaded with fresh, up to date data from the server.
I have been thinking of using Ajax requests to update like every second, but there has to be an other way to do this. Ajax requests will cause a lot data traffic. Also, when using the Facebook chat, you don't have to wait every second, chats are received almost instantly. Yet I don't see any Ajax polling requests being made when I use the developer tools of Mozilla Firefox. This made me think if there would be a different way to do this.
I've looked into Node.js, but it appears that isn't possible with my host.
I have heard people talking about Ajax Push, is that what I should use? If so, can you give me a basic usage example?
If not, what would then be the way to go when having multiple data streams that have to be reloaded within a second?
Requirements are speed and low data traffic. It therefore wouldn't be an option to continuously poll the server, I think, because that would create an enormous overhead.
I don't think it's of any importance, but I'm using PHP5.3 in the back end and JavaScript with jQuery 1.9.1 in the front end.
Answer
This question has been asked a number of times, but in a slightly different ways. Here are a few references that are worth a read:
- What are Long-Polling, Websockets, Server-Sent Events (SSE) and Comet?
- Using comet with PHP?
- Apache with Comet Support
- Server Scalability - HTML 5 websockets vs Comet
- How to implement event listening in PHP
In summary: if you are looking at building your solution using PHP on Apache then holding open persistent connections (HTTP long-polling or streaming) is going to use up resources very quickly (is highly inefficient). So, you would be better using a hosted solution (*disclaimer - I work for a hosted solution).
HTTP-Long polling and HTTP Streaming are solutions which have been superseded by Server-Sent Events and WebSockets. So, where possible (where the web client provides support) you should use one of these solutions before falling back to an HTTP-based solution. A good realtime web technology will automatically handle this for you.
Since your diagram shows you are subscribing to multiple data streams you should also consider a Publish/Subscribe solution that naturally fits with this. Again, a good realtime web tech solution will provide you with this.
Also see the realtime web technology guide.