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

[Nicola Worthington]

That's certainly a possibility, but since this app is primarily aimed at
mobile devices that will be landing directly on stream URLs (for the most
part not launched from their browser but through a handful of other apps
that will simply make a call to the OS to open a URL for them to stream
media directly) it would make this approach less than idea and not as
robust as I was hoping for. :(


On 21 December 2013 03:52, Matthew Mallard <mqm at q-technologies.com.au>wrote:

>  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
>
>
>
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>


-- 
Nicola Worthington
+44 (0)3333 406 333
nicolaw at tfb.net
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