Hi, I have a large script which, among other things, gets output from several external workers. A problem occurs when workers complete at nearly the same time. At least, I think that is the reason. Then, randomly, instead of data, application may receive an empty string.

Here's a watered down version of server:

use strict;
use warnings;
use feature qw/ say /;
use utf8;

use Sereal qw/ sereal_decode_with_object /;
use IO::Async::Loop;
use IO::Async::Listener;
use Future;

$, = "\t";

my $PORT = 53123;
my $num  = 0;
my $dec  = Sereal::Decoder-> new;
my $loop = IO::Async::Loop-> new;
my $lst  = IO::Async::Listener-> new(
     on_stream => sub {
        my ( $self, $stream ) = @_;
        
        $stream-> configure( on_read => sub { 0 });
        $loop-> add( $stream );
        
        $stream-> read_until_eof-> on_ready( sub {
            my $F = shift;
            my ( $buf, $eof ) = $F-> get;

            print ++$num, length( $buf ), unpack( 'H*', $buf ), '';
            say sereal_decode_with_object( $dec, $buf )
        })
    }
);
$loop -> add( $lst );
$lst-> listen(
    addr => {
        family   => 'inet',
        socktype => 'stream',
        ip       => '127.0.0.1',
        port     => $PORT,
    },
)->on_done( sub { say "Listening on $PORT..." });

$loop-> run;
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And here is a simple worker:

use strict;
use warnings;
use feature qw/ say /;
use utf8;
use autodie;
use Sereal qw/ encode_sereal /;
use IO::Socket::INET;

my $PORT = 53123;

say "hi, i'm $$";

while () {
    my $sock = new IO::Socket::INET(
        PeerHost => '127.0.0.1',
        PeerPort => $PORT,
        Proto    => 'tcp',
    ) or die;
    binmode $sock;
    print $sock encode_sereal $$;
    $sock-> close;
    select( undef, undef, undef, 0.01 );
}
[download]

Then I run server and a single worker. After random interval, server crashes:

...
1685    9       3df3726c030020e009      1248
1686    9       3df3726c030020e009      1248
1687    9       3df3726c030020e009      1248
1688    9       3df3726c030020e009      1248
Sereal: Error: Bad Sereal header: Not a valid Sereal document. at offs
+et 1 of input at srl_decoder.c line 573 at server.pl line 29.
1689    0
[download]

Why does it happen and can anything be done about it?