From bd4af1093f3c5704c99379c7538cb6fd62f732f6 Mon Sep 17 00:00:00 2001
From: jbjohnso <jbjohnso@8638fb3e-16cb-4fca-ae20-7b5d299a9bcd>
Date: Fri, 23 Mar 2012 12:55:35 +0000
Subject: [PATCH] Have xCAT more aggressively drain the listen queue on the
 main listening socket. This change manages to have xCAT successfully field a
 large amount of incoming connections with a relatively small listen queue.

git-svn-id: https://svn.code.sf.net/p/xcat/code/xcat-core/branches/2.7@11962 8638fb3e-16cb-4fca-ae20-7b5d299a9bcd
---
 xCAT-server/sbin/xcatd | 24 ++++++++++++++++++++----
 1 file changed, 20 insertions(+), 4 deletions(-)

diff --git a/xCAT-server/sbin/xcatd b/xCAT-server/sbin/xcatd
index 23c05a148..a2e6cd70e 100755
--- a/xCAT-server/sbin/xcatd
+++ b/xCAT-server/sbin/xcatd
@@ -823,6 +823,7 @@ while (not $listener and $retry) {
     }
     sleep(0.05);
 }
+my $listenwatcher = IO::Select->new($listener);
 
 unless ($listener) {
   kill 2, $pid_UDP;
@@ -840,13 +841,28 @@ open($mainpidfile,">","/tmp/xcat/mainservice.pid"); #if here, everyone else has
 print $mainpidfile $$;
 close($mainpidfile);
 closelog();
+my @pendingconnections;
+my $tconn;
 until ($quit) {
   $SIG{CHLD} = \&ssl_reaper; #set here to ensure that signal handler is not corrupted during loop
-  next unless my $cnnection=$listener->accept;
-  my $connection;
-  while ($sslclients > $maxsslclients) { #THROTTLE
-      sleep 0.1; #Keep processor utilization down
+  if (@pendingconnections) {
+	while ($listenwatcher->can_read(0)) { #grab everything we ca
+		$tconn = $listener->accept;
+		unless ($tconn) { next; }
+		push @pendingconnections,$tconn;
+	}
+  } else {
+	$tconn = $listener->accept;
+	unless ($tconn) { next; }
+	push @pendingconnections,$tconn;
   }
+  unless (scalar @pendingconnections) { next; }
+  if ($sslclients > $maxsslclients) { #THROTTLE
+      $listenwatcher->can_read(0.1); #when next connection tries to come in or a tenth of a second, whichever comes first
+      next; #just keep pulling things off listen queue onto our own
+  }
+  my $cnnection=shift @pendingconnections;
+  my $connection;
   my $child = xCAT::Utils->xfork(); #Yes we fork, IO::Socket::SSL is not threadsafe..
   if ($child) {
       $immediatechildren{$child}=1;