问题
I would like some advice on how to implement the following:
I would like to make my users aware of the progress of a task that is running on my server via AJAX. My server runs a PHP script that downloads a file via shell command using the popen function. It periodically echos/prints what is happening. I would like to capture this output using AJAX and present it to the user.
I was told in another question that I might need to make use of polling or comet? I would really appreciate any help or guidance on how to achieve this in the simplest and most efficient way. Hopefully, I can still make use of JQuery.
Thank you all for taking the time to read this.
P.S. I was able to get this far with thanks to the stackoverflow community. :)
回答1:
This sounds like a great opportunity for Ajax long polling, which is one of the myriad techniques used in general Comet implementations. There's another question on Stack Overflow with sample code.
回答2:
The link Jim Puls posted is a great place to start. Lots of users in that questions offer a lot of great information on Comet polling & PHP. Most places I've seen have recommended using python twisted to accomplish this task.
Also, here's a few links to:
Responsive AJAX applications with COMET
A Progress Bar in Jquery
And Another HTTP Streaming AjAx Pattern Article
I would probably go the route gs mentioned in the end depending on how "necessary" the progress bar is. If it's just a feature to help the user realize that it's taking a bit more time than usually to process, then "tricking" them with an estimation is a lot easier than the live polling.
回答3:
I'd just use regular polling instead of comet, as this is more like a hack. To make the UI more fluid you could cheat and update your progress bar without checking with the server, just by calculating the average time it needs to do a task. You could correct the error by polling for the correct status. If you implement that well, everyone will think it's live updating.
来源：https://stackoverflow.com/questions/588284/ajax-progress-bar-polling-comet