[dancer-users] Detecting disconnected HTTP clients during streamed output

[Matthew Mallard]

Just an idea.

Why don't you use ajax and only allow on conversion per user at a time.  
You can create an ajax query to check on progress, plus the user can 
cancel.  Basically detach the conversion from the web client, but allow 
client to check on progress and have access to the file when it has 
finished.

On 21/12/2013 5:40 am, Nicola Worthington wrote:
> I have a handler that transcodes video files using ffmpeg which all 
> works fine. However, if the web client disconnects or otherwise stops 
> reading from the socket, my handler will continue reading from the 
> ffmpeg filehandle and writing out to the writer object until ffmpeg 
> has completed the transcode.
>
> This wouldn't be a problem is we lived in a perfect world where every 
> web client would send a single request to a URL and not make 
> additional requests until the first one had been completed, but of 
> course we don't live in an ideal world,.. and I would prefer my webapp 
> not kill the server it is running on my spawning off more CPU 
> intensive processes than necessary.
>
> Is there any way for me to determine how much data is sat waiting to 
> be flushed to the web client so that if it exceeded a predetermined 
> number of bytes I can assume that I should kill my ffmpeg file handle 
> and exit the handler prematurely,.. or any other way to determine if 
> the web client has gone away?
>
> Apologies if I haven't explained myself especially articulately.
>
> This is the handler in question:
>
> *get '/stream/:file/:format' => sub {*
> *    my $file = params->{file};*
> *    my $format = params->{format};*
> *
> *
> *    return send_file(*
> *'favicon.ico',*
> *        streaming => 1,*
> *        callbacks => {*
> *override => sub {*
> *                my ($respond, $response) = @_;*
> *
> *
> *      my $mime = 'video/mp4';*
> *                my @ffmpeg_args = qw(-threads 0 -i $file);*
> *
> *
> *      if (exists $ffmpeg_formats{$format}) {*
> *  $mime = 'video/' . $format;*
> *  push @ffmpeg_args, @{$ffmpeg_formats{$format}};*
> *                } else {*
> *  push @ffmpeg_args, @{$ffmpeg_formats{mp4}};*
> *                }*
> *push @ffmpeg_args, '-';*
> *
> *
> *                my $writer = $respond->([200, ['Content-Type' => 
> $mime]]);*
> *open(my $fh, '-|', join(' ', '/usr/bin/ffmpeg', @ffmpeg_args));*
> *                my $buffer;*
> *while (read($fh, $buffer, 1024) ) {*
> *  $writer->write($buffer);*
> *                }*
> *close($fh);*
> *            },*
> *        },*
> *    );*
> *};*
>
>
> -- 
> Nicola Worthington
> nicolaw at tfb.net <mailto:nicolaw at tfb.net>
>
>
>
> _______________________________________________
> dancer-users mailing list
> dancer-users at dancer.pm
> http://lists.preshweb.co.uk/mailman/listinfo/dancer-users

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.preshweb.co.uk/pipermail/dancer-users/attachments/20131221/b652fc99/attachment.html>