--- loncom/lti/ltiauth.pm	2019/06/13 17:45:26	1.18
+++ loncom/lti/ltiauth.pm	2019/07/18 18:28:46	1.19
@@ -1,7 +1,7 @@
 # The LearningOnline Network
 # Basic LTI Authentication Module
 #
-# $Id: ltiauth.pm,v 1.18 2019/06/13 17:45:26 raeburn Exp $
+# $Id: ltiauth.pm,v 1.19 2019/07/18 18:28:46 raeburn Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -749,9 +749,21 @@ sub lti_session {
             }
         }
     }
+    my $protocol = 'http';
+    if ($ENV{'SERVER_PORT'} == 443) {
+        $protocol = 'https';
+    }
     if (($is_balancer) && (!$hosthere)) {
         # login but immediately go to switch server.
         &Apache::lonauth::success($r,$uname,$udom,$uhome,'noredirect');
+        if (($ltihash->{'callback'}) && ($params->{$ltihash->{'callback'}})) {
+            &LONCAPA::ltiutils::setup_logout_callback($uname,$udom,$otherserver,
+                                                      $ltihash->{'key'},
+                                                      $ltihash->{'secret'},
+                                                      $params->{$ltihash->{'callback'}},
+                                                      $r->dir_config('ltiIDsDir'),
+                                                      $protocol,$r->hostname);
+        }
         if ($symb) {
             $env{'form.symb'} = $symb;
             $env{'request.lti.uri'} = $tail;
@@ -818,6 +830,14 @@ sub lti_session {
         foreach my $key (%{$params}) {
             delete($env{'form.'.$key});
         }
+        if (($ltihash->{'callback'}) && ($params->{$ltihash->{'callback'}})) {
+            &LONCAPA::ltiutils::setup_logout_callback($uname,$udom,$lonhost,
+                                                      $ltihash->{'key'},
+                                                      $ltihash->{'secret'},
+                                                      $params->{$ltihash->{'callback'}},
+                                                      $r->dir_config('ltiIDsDir'),
+                                                      $protocol,$r->hostname);
+        }
         my $ip = $r->get_remote_host();
         my %info=('ip'        => $ip,
                   'domain'    => $udom,