treewide: "require" + "use" cleanup and docs

[public-inbox.git] / lib / PublicInbox / Listener.pm

diff --git a/lib/PublicInbox/Listener.pm b/lib/PublicInbox/Listener.pm
index 594dabb83e38eacd2b2733c952c205e3ffdc2456..928d9301902fdb059ddbd4a2603af92cb6848736 100644 (file)
--- a/lib/PublicInbox/Listener.pm
+++ b/lib/PublicInbox/Listener.pm
@@ -1,4 +1,4 @@
-# Copyright (C) 2015-2018 all contributors <meta@public-inbox.org>
+# Copyright (C) 2015-2019 all contributors <meta@public-inbox.org>
 # License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
 #
 # Used by -nntpd for listen sockets
@@ -8,15 +8,21 @@ use warnings;
 use base 'PublicInbox::DS';
 use Socket qw(SOL_SOCKET SO_KEEPALIVE IPPROTO_TCP TCP_NODELAY);
 use fields qw(post_accept);
-require IO::Handle;
+use IO::Handle;
 use PublicInbox::Syscall qw(EPOLLIN EPOLLEXCLUSIVE EPOLLET);
+use Errno qw(EAGAIN ECONNABORTED EPERM);
+
+# Warn on transient errors, mostly resource limitations.
+# EINTR would indicate the failure to set NonBlocking in systemd or similar
+my %ERR_WARN = map {;
+       eval("Errno::$_()") => $_
+} qw(EMFILE ENFILE ENOBUFS ENOMEM EINTR);
 
 sub new ($$$) {
        my ($class, $s, $cb) = @_;
        setsockopt($s, SOL_SOCKET, SO_KEEPALIVE, 1);
        setsockopt($s, IPPROTO_TCP, TCP_NODELAY, 1); # ignore errors on non-TCP
        listen($s, 1024);
-       IO::Handle::blocking($s, 0);
        my $self = fields::new($class);
        $self->SUPER::new($s, EPOLLIN|EPOLLET|EPOLLEXCLUSIVE);
        $self->{post_accept} = $cb;
@@ -36,6 +42,18 @@ sub event_step {
                IO::Handle::blocking($c, 0); # no accept4 :<
                $self->{post_accept}->($c, $addr, $sock);
                $self->requeue;
+       } elsif ($! == EAGAIN || $! == ECONNABORTED || $! == EPERM) {
+               # EAGAIN is common and likely
+               # ECONNABORTED is common with bad connections
+               # EPERM happens if firewall rules prevent a connection
+               # on Linux (and everything that emulates Linux).
+               # Firewall rules are sometimes intentional, so we don't
+               # warn on EPERM to avoid being too noisy...
+               return;
+       } elsif (my $sym = $ERR_WARN{int($!)}) {
+               warn "W: accept(): $! ($sym)\n";
+       } else {
+               warn "BUG?: accept(): $!\n";
        }
 }