[Catalyst] Non Blocking File Streaming - write_fh

[John Napiorkowski]

Neil,

You're the man!  Any change I could get this as a pull request on the github repo (is also the sane place I am asking people to submit articles)


https://github.com/perl-catalyst/2013-Advent-Staging

That way I am sure to get the code correct.

The only thing is that when using eval I prefer the following idiom as I think its a little safer

eval { ...; 1 } || die "trouble: $!";

On the other hand since Catalyst already requires Try::Tiny no reason to just not use that.

John



On Friday, December 6, 2013 1:56 AM, neil.lunn <neil at mylunn.id.au> wrote:

Hi all, and mostly John,

I was just browsing through the upcoming Advent code examples when I saw 
the example for this had a bug. The code will die horribly when a call 
is made to HEAD rather than get as the output filehandle gets closed. 
The die is from an uncaught exception on $self->write.

My patch to MyApp::Stream :

sub read_chunk {
   my ($self, $fh, $offset) = @_;
   my $buffer = '';
   aio_read $fh, $offset, 65536, $buffer, 0, sub {
     my $status = shift;
     die "read error[$status]: $!" unless $status >= 0;
     if($status) {
       eval {
         $self->write($buffer);
       };
       if ($@) {
         warn "Cannot write, probably a closed pipe";
       }
       $self->read_chunk($fh, ($offset + 65536));
     } else {
       $self->close;
       aio_close $fh, sub { };
     }
   }
}

So the eval block and the warn, not die as this is not being caught 
under any other exception handler. Real world, YMMV. Not elegant, but 
would probably be better for passing in context.

Also I have a full Advent style writeup of the issue Bill brought up 
recently with explainations and solutions down to making the handle DWIW 
for for transparent handing over to Catalyst. If that is wanted/needed :)

Neil


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