ストリーミングPlackアプリケーションとMiddlewareのスケルトン

app.psgi

#!/usr/bin/perl

use strict;
use warnings;

use FindBin;
use lib $FindBin::Bin . '';

use POSIX qw(EPIPE);
use IO::Select;
use Data::Dumper;

use Plack::Builder;

my $app = sub {
  my $env = shift;
  return sub {
    my $responder = shift;
    my $writer = $responder->([200, ['Content-Type', 'text/plain']]);
    for (my $i=1; $i <= 10; $i++) {
      my $w = $writer->write("$i\n");
      if ($! == EPIPE) {
        warn "Broken pipe.\n";
        last;
      }
    }
    warn "DONE\n";
    $writer->close;
  };
};

builder {
    enable "Foo", file_etag => [qw/size/];
    $app;
};

Foo.pm

package Plack::Middleware::Foo;
use parent qw( Plack::Middleware );

sub call {
    my ($self, $env) = @_;
    warn "middleware pre\n";
    my $res = $self->app->($env);
    warn "middleware post\n";
    return Plack::Util::response_cb($res,
        sub {
            my $res = shift;
            # do something with $res;
            warn "middleware response_cb\n";
        }
    );
}

1;