Terminates after sigpipe if client close connection [rt.cpan.org #85904]

[oalders]

Migrated from rt.cpan.org#85904 (status was 'new')

Requestors:

• victor@vsespb.ru

From victor@vsespb.ru on 2013-06-05 19:36:40
:

This behaviour is observed at least last ~5 years, so I am not sure maybe it's a feature.

I can submit PoC if required.

From victor@vsespb.ru on 2014-06-10 19:11:29
:

On Wed Jun 05 23:36:40 2013, vsespb wrote:
> This behaviour is observed at least last ~5 years, so I am not sure
> maybe it's a feature.
> 
> I can submit PoC if required.

====

use strict;
use warnings;
use HTTP::Daemon;

my $PORT = 55001;

if (fork()) { # parent
	#$SIG{PIPE}=sub{die "HEY\n";};
	my $d = HTTP::Daemon->new(Timeout => 20, LocalAddr => '127.0.0.1', LocalPort => $PORT);
	while (my $c = $d->accept) {
		my $r = $c->get_request;
		my $body = "x" x 100_000;
		my $resp = HTTP::Response->new(200, 'OK', [], $body);
		$c->send_response($resp);
		print STDERR "sent\n";
		$c = undef;  # close connection
	}
	print "DONE\n";
	wait;
} else { # child
	my $sock = IO::Socket::INET->new(PeerAddr => '127.0.0.1', PeerPort => $PORT, Proto    => 'tcp');
	print $sock "GET /\n\n";
	close $sock;
}


====

perl daemonpoc.pl || echo $?
will print 141. this means SIGPIPE (SIGPIPE number is 13 + 128 = 141).

also if you uncomment 
#$SIG{PIPE}=sub{die "HEY\n";};
it will print "HEY"

I think it something that should be at least documented.
people who use high level API like $c->send_response($resp); have insperation that they don't do low level things like writings to the sockets, so they are not expect they need to handle SIGPIPE.

[ArenT1981]

Thanks for this heads up. Came across this as I had a head-scratching issue where my Perl server kept quitting, with no apparent error and nothing I was doing was trapping it. Turns out it was this issue, presumably the React client app I had built was closing the connection early due to caching or whatever, in any case, the exiting of the server was completely unnecessary since the client app was in a consistent state.

Putting

$SIG{PIPE} = \&sigpipe_warning;

...

sub sigpipe_warning
{
    print colored("Received SIGPIPE (141). Ignoring.", 'bright_green', 'bold'), "\n";
}

Was all I needed in my code for everything to work as intended, and stop the server quitting early/unnecessarily. Obviously for other applications/use-cases, it may be necessary to do more than simply disregard the error, depending on what you're building and the behaviour you need.

[oalders]

Thanks for this, @ArenT1981!