Hi Flint.

Not sure if you have a solution to this yet, or if I fully understand! But
if your issue is basically that you have a situation where you might have
orphaned processes that never finish and that are consuming real resources
you could have the app get/monitor the process ID for each process you
create, and then simply periodically check to see if that process is in a
run state.

Bow, if the situation is one where the user aborts the transfer process, and
the underlying processes are still 'running' then I would still think the
above appproach would work, but you'd have to have your app keep track of
when the user 'kills' the download process..

But are you sure the orphaned processes are consuming resources, or are they
zombie processes, which are resident in the process tbl, but aren't really
consuming resources... sombie processes will (should) eventually be dealt
with by the operating system...


-----Original Message-----
From: Flint Million [mailto:fmill...@gmail.com]
Sent: Wednesday, May 27, 2009 11:39 PM
To: php-general@lists.php.net
Subject: [PHP] spawning a process that uses pipes - doesn't terminate
when webpage download is canceled

so here's the scenario..

I have a site that uses php with a database to offer sound files to
users using streaming methods.

the request page has options, allowing the user to modify the sound
file in various ways, before having it sent to them

Here's the problem:

The method i'm using to feed the data to the user is to run the source
file through various piped commands, with the resulting audio being
dumped to stdout, and then using passthru in php to get that data to
the enduser.

here's an example, for serving an MP3 with its pitch/speed changed by sox:

passthru("lame --quiet --decode \"" . $in_file . "\" - | " .
             "sox -V -S -t wav - -t wav - speed " . $speed_factor . " | " .
             "lame --quiet " . $lame_params . " - -");

This works just fine, except the problem is if the end user aborts the
transfer (e.g. stops playback in the media player, cancels download of
the mp3, whatever) then it leaves behind both the sox process and the
decoder LAMe process along with the sh that's running them. the only
process that exits is the final encoding lame process. If the sound
file runs to completion, everythign exits properly.

But this obviously means enough "cancelling" of downloads means the
server ends up with a huge batch of stuck processes! And I even tried
simply killing the 'host' sh process, and the lame and sox processes
remain anyway. The only way I've been able to deal with this is
manually killing the lame and sox processes directly.

is there any way I can make this work, such so that if the user
cancels the transfer, all relavent processes are killed rather than
just the single process that's feeding output into php?


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