php started process that ends when viewer leaves page

Question

I have a page streaming mjpegs. I used ffmpeg to generate the mjpegs, and it uses enough CPU that I would like to only have it run when someone is actively viewing the page. My thought was to start it with exec() however, it keeps running when I leave the page, and actually starts multiple instances if I then go back to the page.

Is there a way to kill a process when someone is no longer on a page? My only thought was to use ajax to send a keep alive signal to another program on the server which would kill the process if the signal isn't recieved for > 10 seconds, however it seems like there must be a less convoluted method for doing this.

Agu Dondo · Accepted Answer · 2017-05-04 16:55:41Z

1

There's no way to know from PHP when a user leaves the page unless you make another request from javascript, your approach of the ajax request is a good idea. You can also use the javascript event onbeforeunload to make a request when the user unloads the page to terminate the process.

answered May 4, 2017 at 16:55

Agu Dondo

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Agu Dondo Over a year ago

Remember Javascript can always fail and not be executed for security reasons, or not at all if the user has JavaScript turned off.

jeffpkamp Over a year ago

so if I start and stop the stream with javascript that will deal with someone not having it enabled... then I just have to worry about their browser completely crashing I suppose.

jeffpkamp Over a year ago

I realized if multiple people are watching and one leaves then that kills the feed for every one else... any ideas on working around that?

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