listener: support multi-accept like nginx

While accepting a single connection at-a-time is likely best for
multi-worker and/or load-balanced deployments; accepting
multiple connections at once should be less bad on overloaded
single-worker systems.

We can't automatically pick the best value here since worker
counts are dynamic via SIGTTIN/SIGTTOU.  Process managers
(e.g. systemd) can also spawn multiple instances sharing a
single listener with no knowledge sharing between listeners.

1 files changed, 6 insertions, 2 deletions

diff --git a/lib/PublicInbox/Daemon.pm b/lib/PublicInbox/Daemon.pm
index 57435421..30442227 100644
--- a/lib/PublicInbox/Daemon.pm
+++ b/lib/PublicInbox/Daemon.pm
@@ -136,6 +136,8 @@ sub load_mod ($;$$) {
         }
         my $err = $tlsd->{err};
         $tlsd->{warn_cb} = sub { print $err @_ }; # for local $SIG{__WARN__}
+        $opt->{'multi-accept'} and
+                $xn{'multi-accept'} = $opt->{'multi-accept'}->[-1];
         \%xn;
 }
 
@@ -167,6 +169,7 @@ EOF
                 'u|user=s' => \$user,
                 'g|group=s' => \$group,
                 'D|daemonize' => \$daemonize,
+                'multi-accept=i' => \$PublicInbox::Listener::MULTI_ACCEPT,
                 'cert=s' => \$default_cert,
                 'key=s' => \$default_key,
                 'help|h' => \(my $show_help),
@@ -251,7 +254,7 @@ EOF
                 $s->blocking(0);
                 my $sockname = sockname($s);
                 warn "# bound $scheme://$sockname\n";
-                $xnetd->{$sockname} //= load_mod($scheme);
+                $xnetd->{$sockname} //= load_mod($scheme, $opt);
                 $listener_names->{$sockname} = $s;
                 push @listeners, $s;
         }
@@ -712,7 +715,8 @@ sub daemon_loop ($) {
                 defer_accept($_, $tls_cb ? 'dataready' : $xn->{af_default});
 
                 # this calls epoll_create:
-                PublicInbox::Listener->new($_, $tls_cb || $xn->{post_accept})
+                PublicInbox::Listener->new($_, $tls_cb || $xn->{post_accept},
+                                                $xn->{'multi-accept'})
         } @listeners;
         PublicInbox::DS::event_loop($sig, $oldset);
 }