--- loncom/lonnet/perl/lonnet.pm	2018/07/18 13:45:03	1.1379
+++ loncom/lonnet/perl/lonnet.pm	2018/08/09 14:04:35	1.1381
@@ -1,7 +1,7 @@
 # The LearningOnline Network
 # TCP networking package
 #
-# $Id: lonnet.pm,v 1.1379 2018/07/18 13:45:03 raeburn Exp $
+# $Id: lonnet.pm,v 1.1381 2018/08/09 14:04:35 raeburn Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -10041,12 +10041,25 @@ sub is_course {
     my ($cdom, $cnum) = scalar(@_) == 1 ? 
          ($_[0] =~ /^($match_domain)_($match_courseid)$/)  :  @_;
 
-    return unless $cdom and $cnum;
-
-    my %courses = &courseiddump($cdom, '.', 1, '.', '.', $cnum, undef, undef,
-        '.');
-
-    return unless(exists($courses{$cdom.'_'.$cnum}));
+    return unless (($cdom =~ /^$match_domain$/) && ($cnum =~ /^$match_courseid$/));
+    my $uhome=&homeserver($cnum,$cdom);
+    my $iscourse;
+    if (grep { $_ eq $uhome } current_machine_ids()) {
+        $iscourse = &Lond::is_course($cdom,$cnum);
+    } else {
+        my $hashid = $cdom.':'.$cnum;
+        ($iscourse,my $cached) = &is_cached_new('iscourse',$hashid);
+        unless (defined($cached)) {
+            my %courses = &courseiddump($cdom, '.', 1, '.', '.',
+                                        $cnum,undef,undef,'.');
+            $iscourse = 0;
+            if (exists($courses{$cdom.'_'.$cnum})) {
+                $iscourse = 1;
+            }
+            &do_cache_new('iscourse',$hashid,$iscourse,3600);
+        }
+    }
+    return unless ($iscourse);
     return wantarray ? ($cdom, $cnum) : $cdom.'_'.$cnum;
 }
 
@@ -13629,7 +13642,7 @@ sub fetch_crl_pemfile {
 
 sub save_crl_pem {
     my ($response) = @_;
-    my $msg;
+    my ($msg,$hadchanges);
     if (ref($response)) {
         my $now = time;
         my $lonca = $perlvar{'lonCertificateDirectory'}.'/'.$perlvar{'lonnetCertificateAuthority'};
@@ -13644,11 +13657,43 @@ sub save_crl_pem {
                     chomp($check);
                     if ($check eq 'verify OK') {
                         my $dest = "$perlvar{'lonCertificateDirectory'}/$perlvar{'lonnetCertRevocationList'}";
+                        my $backup;
                         if (-e $dest) {
-                            &File::Copy::move($dest,"$dest.bak");
+                            if (&File::Copy::move($dest,"$dest.bak")) {
+                                $backup = 'ok';
+                            }
                         }
                         if (&File::Copy::move($tmpcrl,$dest)) {
                             $msg = 'ok';
+                            if ($backup) {
+                                my (%oldnums,%newnums);
+                                if (open(PIPE, "openssl crl -inform PEM -text -noout -in $dest.bak |grep 'Serial Number' |")) {
+                                    while (<PIPE>) {
+                                        $oldnums{(split(/:/))[1]} = 1;
+                                    }
+                                    close(PIPE);
+                                }
+                                if (open(PIPE, "openssl crl -inform PEM -text -noout -in $dest |grep 'Serial Number' |")) {
+                                    while(<PIPE>) {
+                                        $newnums{(split(/:/))[1]} = 1;
+                                    }
+                                    close(PIPE);
+                                }
+                                foreach my $key (sort {$b <=> $a } (keys(%newnums))) {
+                                    unless (exists($oldnums{$key})) {
+                                        $hadchanges = 1;
+                                        last;
+                                    }
+                                }
+                                unless ($hadchanges) {
+                                    foreach my $key (sort {$b <=> $a } (keys(%oldnums))) {
+                                        unless (exists($newnums{$key})) {
+                                            $hadchanges = 1;
+                                            last;
+                                        }
+                                    }
+                                }
+                            }
                         }
                     } else {
                         unlink($tmpcrl);
@@ -13661,7 +13706,7 @@ sub save_crl_pem {
             }
         }
     }
-    return $msg;
+    return ($msg,$hadchanges);
 }
 
 # ------------------------------------------------------------ Read domain file