Question

I am developing a video upload site and I have ran into a dilemma: videos uploaded need to be converted into the FLV format in order to be displayed to a visitor but, if I execute the command within the script, the script will hang for about 10-15 minutes while the FFMPEG converts the video.

I had an idea to insert a record in to the database indicating the file needs to be processed, then using a cron job set to every 5 minutes to select records from the database which needs to be processed, process them, then update the database showing they have been processed. My worry about this is executing too many processes and the server crashing under the strain, so has anyone got any solutions to this or a way to better the process I have in mind?

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Okay, this is now what I have in mind, so the user uploads a video and a row is inserted in to the database indicating the video needs to be processed. A cron job set to every 5 minutes checks what needs to be processed and what is being processed, say I would make a maximum of five processes at one time, so the script would check if any video needs to be processed and how many videos are being processed, if it is less then five, it updates the record indicating that it is being processed, once the video has been processed, it updates the record indicating it has been processed and the cron job starts again, any thoughts?

Answer 1

If you expect a lot of traffic you should seriously consider a dedicated server.

On a single server, you can use shell_exec along with the UNIX nohup command to get the PID of the process.

   function run_in_background($Command, $Priority = 0)
   {
       if($Priority)
           $PID = shell_exec("nohup nice -n $Priority $Command 2> /dev/null & echo $!");
       else
           $PID = shell_exec("nohup $Command 2> /dev/null & echo $!");
       return($PID);
   }
   function is_process_running($PID)
   {
       exec("ps $PID", $ProcessState);
       return(count($ProcessState) >= 2);
   }

A full description of this technique is here: http://nsaunders.wordpress.com/2007/01/12/running-a-background-process-in-php/

You could perhaps put the list of PIDs in a MySQL table and then use your cron job every 5 mins to detect when a video is complete and update the relevant values in the database.