--- loncom/loncnew	2003/07/03 02:10:18	1.14
+++ loncom/loncnew	2003/12/11 23:18:37	1.34
@@ -2,13 +2,12 @@
 # The LearningOnline Network with CAPA
 # lonc maintains the connections to remote computers
 #
-# $Id: loncnew,v 1.14 2003/07/03 02:10:18 foxr Exp $
+# $Id: loncnew,v 1.34 2003/12/11 23:18:37 albertel Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
 # This file is part of the LearningOnline Network with CAPA (LON-CAPA).
-#
-# LON-CAPA is free software; you can redistribute it and/or modify
+## LON-CAPA is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
 # the Free Software Foundation; either version 2 of the License, or
 # (at your option) any later version.
@@ -27,7 +26,7 @@
 # http://www.lon-capa.org/
 #
 #
-# new lonc handles n requestors spread out bver m connections to londs.
+# new lonc handles n request out bver m connections to londs.
 # This module is based on the Event class.
 #   Development iterations:
 #    - Setup basic event loop.   (done)
@@ -44,37 +43,8 @@
 #    - Detect transmission timeouts.
 #
 
-# Change log:
-#    $Log: loncnew,v $
-#    Revision 1.14  2003/07/03 02:10:18  foxr
-#    Get all of the signals to work correctly.
-#
-#    Revision 1.13  2003/07/02 01:31:55  foxr
-#    Added kill -HUP logic (restart).
-#
-#    Revision 1.11  2003/06/25 01:54:44  foxr
-#    Fix more problems with transaction failure.
-#
-#    Revision 1.10  2003/06/24 02:46:04  foxr
-#    Put a limit on  the number of times we'll retry a connection.
-#    Start getting the signal stuff put in as well...note that need to get signals
-#    going or else 6the client will permanently give up on dead servers.
-#
-#    Revision 1.9  2003/06/13 02:38:43  foxr
-#    Add logging in 'expected format'
-#
-#    Revision 1.8  2003/06/11 02:04:35  foxr
-#    Support delayed transactions... this is done uniformly by encapsulating
-#    transactions in an object ... a LondTransaction that is implemented by
-#    LondTransaction.pm
-#
-#    Revision 1.7  2003/06/03 01:59:39  foxr
-#    complete coding to support deferred transactions.
-#
-#
-
+use strict;
 use lib "/home/httpd/lib/perl/";
-use lib "/home/foxr/newloncapa/types";
 use Event qw(:DEFAULT );
 use POSIX qw(:signal_h);
 use POSIX;
@@ -96,12 +66,6 @@ use LONCAPA::HashIterator;
 #
 #   Disable all signals we might receive from outside for now.
 #
-#$SIG{QUIT}  = IGNORE;
-#$SIG{HUP}   = IGNORE;
-#$SIG{USR1}  = IGNORE;
-#$SIG{INT}   = IGNORE;
-#$SIG{CHLD}  = IGNORE;
-#$SIG{__DIE__}  = IGNORE;
 
 
 # Read the httpd configuration file to get perl variables
@@ -114,19 +78,22 @@ my %perlvar    = %{$perlvarref};
 #  parent and shared variables.
 
 my %ChildHash;			# by pid -> host.
+my %HostToPid;			# By host -> pid.
+my %HostHash;			# by loncapaname -> IP.
 
 
 my $MaxConnectionCount = 10;	# Will get from config later.
 my $ClientConnection = 0;	# Uniquifier for client events.
 
 my $DebugLevel = 0;
+my $NextDebugLevel= 2;		# So Sigint can toggle this.
 my $IdleTimeout= 3600;		# Wait an hour before pruning connections.
 
 #
 #  The variables below are only used by the child processes.
 #
 my $RemoteHost;			# Name of host child is talking to.
-my $UnixSocketDir= "/home/httpd/sockets"; 
+my $UnixSocketDir= $perlvar{'lonSockDir'};
 my $IdleConnections = Stack->new(); # Set of idle connections
 my %ActiveConnections;		# Connections to the remote lond.
 my %ActiveTransactions;		# LondTransactions in flight.
@@ -136,8 +103,8 @@ my $ConnectionCount = 0;
 my $IdleSeconds     = 0;	# Number of seconds idle.
 my $Status          = "";	# Current status string.
 my $RecentLogEntry  = "";
-my $ConnectionRetries=5;	# Number of connection retries allowed.
-my $ConnectionRetriesLeft=5;	# Number of connection retries remaining.
+my $ConnectionRetries=2;	# Number of connection retries allowed.
+my $ConnectionRetriesLeft=2;	# Number of connection retries remaining.
 
 #
 #   The hash below gives the HTML format for log messages
@@ -235,7 +202,7 @@ sub GetPeername {
     my $peerip;
     if($AdrFamily == AF_INET) {
 	($peerport, $peerip) = sockaddr_in($peer);
-	my $peername    = gethostbyaddr($iaddr, $AdrFamily);
+	my $peername    = gethostbyaddr($peerip, $AdrFamily);
 	return $peername;
     } elsif ($AdrFamily == AF_UNIX) {
 	my $peerfile;
@@ -256,7 +223,7 @@ sub Debug {
     my $level   = shift;
     my $message = shift;
     if ($level <= $DebugLevel) {
-	print $message." host = ".$RemoteHost."\n";
+	Log("INFO", "-Debug- $message host = $RemoteHost");
     }
 }
 
@@ -286,6 +253,23 @@ sub ShowStatus {
 
 =pod
 
+=head 2 SocketTimeout
+
+    Called when an action on the socket times out.  The socket is 
+   destroyed and any active transaction is failed.
+
+
+=cut
+sub SocketTimeout {
+    my $Socket = shift;
+    
+    KillSocket($Socket);	# A transaction timeout also counts as
+                                # a connection failure:
+    $ConnectionRetriesLeft--;
+}
+
+=pod
+
 =head2 Tick
 
 Invoked  each timer tick.
@@ -295,8 +279,12 @@ Invoked  each timer tick.
 
 sub Tick {
     my $client;
-    ShowStatus(GetServerHost()." Connection count: ".$ConnectionCount);
-
+    if($ConnectionRetriesLeft > 0) {
+	ShowStatus(GetServerHost()." Connection count: ".$ConnectionCount
+		   ." Retries remaining: ".$ConnectionRetriesLeft);
+    } else {
+	ShowStatus(GetServerHost()." >> DEAD <<");
+    }
     # Is it time to prune connection count:
 
 
@@ -304,13 +292,27 @@ sub Tick {
        ($WorkQueue->Count() == 0)) { # Idle connections and nothing to do?
 	$IdleSeconds++;
 	if($IdleSeconds > $IdleTimeout) { # Prune a connection...
-	    $Socket = $IdleConnections->pop();
+	    my $Socket = $IdleConnections->pop();
 	    KillSocket($Socket);
 	}
     } else {
 	$IdleSeconds = 0;	# Reset idle count if not idle.
     }
-
+    #
+    #  For each inflight transaction, tick down its timeout counter.
+    #
+    foreach my $item (keys %ActiveTransactions) {
+	my $Socket = $ActiveTransactions{$item}->getServer();
+	$Socket->Tick();
+    }
+    foreach my $item (keys %ActiveConnections) {
+	my $State = $ActiveConnections{$item}->data->GetState();
+	if ($State ne 'Idle' && $State ne 'SendingRequest' &&
+	    $State ne 'ReceivingReply') {
+	    Debug(5,"Ticking Socket $State $item");
+	    $ActiveConnections{$item}->data->Tick();
+	}
+    }
     # Do we have work in the queue, but no connections to service them?
     # If so, try to make some new connections to get things going again.
     #
@@ -320,12 +322,18 @@ sub Tick {
 	if ($ConnectionRetriesLeft > 0) {
 	    my $Connections = ($Requests <= $MaxConnectionCount) ?
 		$Requests : $MaxConnectionCount;
-	    Debug(1,"Work but no connections, start ".$Connections." of them");
-	    for ($i =0; $i < $Connections; $i++) {
-		MakeLondConnection();
+	    Debug(5,"Work but no connections, start ".$Connections." of them");
+	    my $successCount = 0;
+	    for (my $i =0; $i < $Connections; $i++) {
+		$successCount += MakeLondConnection();
+	    }
+	    if($successCount == 0) { # All connections failed:
+		Debug(5,"Work in queue failed to make any connectiouns\n");
+		EmptyQueue();	# Fail pending transactions with con_lost.
 	    }
 	} else {
-	    Debug(1,"Work in queue, but gave up on connections..flushing\n");
+	    ShowStatus(GetServerHost()." >>> DEAD!!! <<<");
+	    Debug(5,"Work in queue, but gave up on connections..flushing\n");
 	    EmptyQueue();	# Connections can't be established.
 	}
        
@@ -350,7 +358,7 @@ Trigger disconnections of idle sockets.
 
 sub SetupTimer {
     Debug(6, "SetupTimer");
-    Event->timer(interval => 1, debug => 1, cb => \&Tick );
+    Event->timer(interval => 1, cb => \&Tick );
 }
 
 =pod
@@ -372,19 +380,19 @@ sub ServerToIdle {
     my $Socket   = shift;	# Get the socket.
     delete($ActiveTransactions{$Socket}); # Server has no transaction
 
-    &Debug(6, "Server to idle");
+    &Debug(5, "Server to idle");
 
     #  If there's work to do, start the transaction:
 
-    $reqdata = $WorkQueue->dequeue(); # This is a LondTransaction
-    unless($reqdata eq undef)  {
-	Debug(9, "Queue gave request data: ".$reqdata->getRequest());
+    my $reqdata = $WorkQueue->dequeue(); # This is a LondTransaction
+    if ($reqdata ne undef)  {
+	Debug(5, "Queue gave request data: ".$reqdata->getRequest());
 	&StartRequest($Socket,  $reqdata);
 
     } else {
 	
     #  There's no work waiting, so push the server to idle list.
-	&Debug(8, "No new work requests, server connection going idle");
+	&Debug(5, "No new work requests, server connection going idle");
 	$IdleConnections->push($Socket);
     }
 }
@@ -430,7 +438,7 @@ sub ClientWritable {
 	# request.
 	
 	&Debug(9,"Send result is ".$result." Defined: ".defined($result));
-	if(defined($result)) {
+	if($result ne undef) {
 	    &Debug(9, "send result was defined");
 	    if($result == length($Data)) { # Entire string sent.
 		&Debug(9, "ClientWritable data all written");
@@ -448,6 +456,12 @@ sub ClientWritable {
 		
 	    } else {		# Partial string sent.
 		$Watcher->data(substr($Data, $result));
+		if($result == 0) {    # client hung up on us!!
+		    Log("INFO", "lonc pipe client hung up on us!");
+		    $Watcher->cancel;
+		    $Socket->shutdown(2);
+		    $Socket->close();
+		}
 	    }
 	    
 	} else {			# Error of some sort...
@@ -495,7 +509,7 @@ The transaction that is being completed.
 =cut
 
 sub CompleteTransaction {
-    &Debug(6,"Complete transaction");
+    &Debug(5,"Complete transaction");
     my $Socket = shift;
     my $Transaction = shift;
 
@@ -504,7 +518,7 @@ sub CompleteTransaction {
 	StartClientReply($Transaction, $data);
     } else {			# Delete deferred transaction file.
 	Log("SUCCESS", "A delayed transaction was completed");
-	LogPerm("S:$Client:".$Transaction->getRequest());
+	LogPerm("S:$Transaction->getClient() :".$Transaction->getRequest());
 	unlink $Transaction->getFile();
     }
 }
@@ -534,7 +548,6 @@ sub StartClientReply {
     &Debug(8," Reply was: ".$data);
     my $Serial         = $ActiveClients{$Client};
     my $desc           = sprintf("Connection to lonc client %d",
-
 				 $Serial);
     Event->io(fd       => $Client,
 	      poll     => "w",
@@ -565,12 +578,16 @@ Parameters:
 
 sub FailTransaction {
     my $transaction = shift;
+    Log("WARNING", "Failing transaction ".$transaction->getRequest());
     Debug(1, "Failing transaction: ".$transaction->getRequest());
     if (!$transaction->isDeferred()) { # If the transaction is deferred we'll get to it.
 	my $client  = $transaction->getClient();
 	Debug(1," Replying con_lost to ".$transaction->getRequest());
 	StartClientReply($transaction, "con_lost\n");
     }
+    if($ConnectionRetriesLeft <= 0) {
+	Log("CRITICAL", "Host marked dead: ".GetServerHost());
+    }
 
 }
 
@@ -582,6 +599,7 @@ sub FailTransaction {
 
 =cut
 sub EmptyQueue {
+    $ConnectionRetriesLeft--;	# Counts as connection failure too.
     while($WorkQueue->Count()) {
 	my $request = $WorkQueue->dequeue(); # This is a transaction
 	FailTransaction($request);
@@ -596,7 +614,7 @@ Close all connections open on lond prior
 
 =cut
 sub CloseAllLondConnections {
-    foreach $Socket (keys %ActiveConnections) {
+    foreach my $Socket (keys %ActiveConnections) {
 	KillSocket($Socket);
     }
 }
@@ -627,6 +645,7 @@ nonzero if we are allowed to create a ne
 sub KillSocket {
     my $Socket = shift;
 
+    Log("WARNING", "Shutting down a socket");
     $Socket->Shutdown();
 
     #  If the socket came from the active connection set,
@@ -647,7 +666,7 @@ sub KillSocket {
     #  work queue, the work all gets failed with con_lost.
     #
     if($ConnectionCount == 0) {
-	EmptyQueue;
+	EmptyQueue();
     }
 }
 
@@ -716,25 +735,28 @@ sub LondReadable {
     my $Socket     = $Watcher->data;
     my $client     = undef;
 
-    &Debug(6,"LondReadable called state = ".$State);
+    &Debug(6,"LondReadable called state = ".$Socket->GetState());
 
 
     my $State = $Socket->GetState(); # All action depends on the state.
 
     SocketDump(6, $Socket);
     my $status = $Socket->Readable();
+
     &Debug(2, "Socket->Readable returned: $status");
 
     if($status != 0) {
 	 # bad return from socket read. Currently this means that
 	# The socket has become disconnected. We fail the transaction.
 
+	Log("WARNING",
+	    "Lond connection lost.");
 	if(exists($ActiveTransactions{$Socket})) {
-	    Debug(3,"Lond connection lost failing transaction");
 	    FailTransaction($ActiveTransactions{$Socket});
 	}
 	$Watcher->cancel();
 	KillSocket($Socket);
+	$ConnectionRetriesLeft--;       # Counts as connection failure
 	return;
     }
     SocketDump(6,$Socket);
@@ -768,9 +790,13 @@ sub LondReadable {
     } elsif ($State eq "Idle") {
 	# If necessary, complete a transaction and then go into the
 	# idle queue.
+	#  Note that a trasition to idle indicates a live lond
+	# on the other end so reset the connection retries.
+	#
+	$ConnectionRetriesLeft = $ConnectionRetries; # success resets the count
 	$Watcher->cancel();
 	if(exists($ActiveTransactions{$Socket})) {
-	    Debug(8,"Completing transaction!!");
+	    Debug(5,"Completing transaction!!");
 	    CompleteTransaction($Socket, 
 				$ActiveTransactions{$Socket});
 	} else {
@@ -880,6 +906,7 @@ sub LondWritable {
 	    # We'll treat this as if the socket got disconnected:
 	    Log("WARNING", "Connection to ".$RemoteHost.
 		" has been disconnected");
+	    FailTransaction($ActiveTransactions{$Socket});
 	    $Watcher->cancel();
 	    KillSocket($Socket);
 	    return;
@@ -979,8 +1006,7 @@ sub QueueDelayed {
     Debug(4, "Delayed path: ".$path);
     opendir(DIRHANDLE, $path);
     
-    @alldelayed = grep /\.$RemoteHost$/, readdir DIRHANDLE;
-    Debug(4, "Got ".$alldelayed." delayed files");
+    my @alldelayed = grep /\.$RemoteHost$/, readdir DIRHANDLE;
     closedir(DIRHANDLE);
     my $dfname;
     my $reqfile;
@@ -1017,26 +1043,27 @@ sub MakeLondConnection {
     my $Connection = LondConnection->new(&GetServerHost(),
 					 &GetServerPort());
 
-    if($Connection == undef) {	# Needs to be more robust later.
+    if($Connection eq undef) {	# Needs to be more robust later.
 	Log("CRITICAL","Failed to make a connection with lond.");
 	$ConnectionRetriesLeft--;
 	return 0;		# Failure.
     }  else {
-	$ConnectionRetriesLeft = $ConnectionRetries; # success resets the count
+
 	# The connection needs to have writability 
 	# monitored in order to send the init sequence
 	# that starts the whole authentication/key
 	# exchange underway.
 	#
 	my $Socket = $Connection->GetSocket();
-	if($Socket == undef) {
+	if($Socket eq undef) {
 	    die "did not get a socket from the connection";
 	} else {
 	    &Debug(9,"MakeLondConnection got socket: ".$Socket);
 	}
 	
-	
-	$event = Event->io(fd       => $Socket,
+	$Connection->SetTimeoutCallback(\&SocketTimeout);
+
+	my $event = Event->io(fd       => $Socket,
 			   poll     => 'w',
 			   cb       => \&LondWritable,
 			   data     => $Connection,
@@ -1092,7 +1119,7 @@ sub StartRequest {
     $ActiveTransactions{$Lond} = $Request;
 
     $Lond->InitiateTransaction($Request->getRequest());
-    $event = Event->io(fd      => $Socket,
+    my $event = Event->io(fd      => $Socket,
 		       poll    => "w",
 		       cb      => \&LondWritable,
 		       data    => $Lond,
@@ -1131,11 +1158,18 @@ sub QueueTransaction {
 
     my $LondSocket    = $IdleConnections->pop();
     if(!defined $LondSocket) {	# Need to queue request.
-	Debug(8,"Must queue...");
+	Debug(5,"Must queue...");
 	$WorkQueue->enqueue($requestData);
 	if($ConnectionCount < $MaxConnectionCount) {
-	    Debug(4,"Starting additional lond connection");
-	    MakeLondConnection();
+	    if($ConnectionRetriesLeft > 0) {
+		Debug(5,"Starting additional lond connection");
+		if(MakeLondConnection() == 0) {
+		    EmptyQueue();	# Fail transactions, can't make connection.
+		}
+	    } else {
+		ShowStatus(GetServerHost()." >>> DEAD !!!! <<<");
+		EmptyQueue();	# It's worse than that ... he's dead Jim.
+	    }
 	}
     } else {			# Can start the request:
 	Debug(8,"Can start...");
@@ -1166,7 +1200,7 @@ sub ClientRequest {
     my $rv = $socket->recv($thisread, POSIX::BUFSIZ, 0);
     Debug(8, "rcv:  data length = ".length($thisread)
 	  ." read =".$thisread);
-    unless (defined $rv && length($thisread)) {
+    unless (defined $rv  && length($thisread)) {
 	 # Likely eof on socket.
 	Debug(5,"Client Socket closed on lonc for ".$RemoteHost);
 	close($socket);
@@ -1300,6 +1334,8 @@ sub SetupLoncListener {
 Child USR1 signal handler to report the most recent status
 into the status file.
 
+We also use this to reset the retries count in order to allow the
+client to retry connections with a previously dead server.
 =cut
 sub ChildStatus {
     my $event = shift;
@@ -1310,6 +1346,7 @@ sub ChildStatus {
     my $fh = IO::File->new(">>$docdir/lon-status/loncstatus.txt");
     print $fh $$."\t".$RemoteHost."\t".$Status."\t".
 	$RecentLogEntry."\n";
+    $ConnectionRetriesLeft = $ConnectionRetries;
 }
 
 =pod
@@ -1326,16 +1363,31 @@ sub SignalledToDeath {
     my $watcher= $event->w;
 
     Debug(2,"Signalled to death! via ".$watcher->data);
-    my ($signal) = @_;
+    my ($signal) = $watcher->data;
     chomp($signal);
     Log("CRITICAL", "Abnormal exit.  Child $$ for $RemoteHost "
 	."died through "."\"$signal\"");
     LogPerm("F:lonc: $$ on $RemoteHost signalled to death: "
 	    ."\"$signal\"");
-    die("Signal abnormal end");
     exit 0;
 
 }
+
+=head2 ToggleDebug
+
+This sub toggles trace debugging on and off.
+
+=cut
+
+sub ToggleDebug {
+    my $Current    = $DebugLevel;
+       $DebugLevel = $NextDebugLevel;
+       $NextDebugLevel = $Current;
+
+    Log("SUCCESS", "New debugging level for $RemoteHost now $DebugLevel");
+
+}
+
 =head2 ChildProcess
 
 This sub implements a child process for a single lonc daemon.
@@ -1348,12 +1400,6 @@ sub ChildProcess {
     #
     #  Signals must be handled by the Event framework...
 #
-#    $SIG{QUIT}  = \&SignalledToDeath;
-#    $SIG{HUP}   = \&ChildStatus;
-#    $SIG{USR1}  = IGNORE;
-#    $SIG{INT}   = DEFAULT;
-#    $SIG{CHLD}  = IGNORE;
-#    $SIG{__DIE__}  = \&SignalledToDeath;
 
     Event->signal(signal   => "QUIT",
 		  cb       => \&SignalledToDeath,
@@ -1364,6 +1410,9 @@ sub ChildProcess {
     Event->signal(signal   => "USR1",
 		  cb       => \&ChildStatus,
 		  data     => "USR1");
+    Event->signal(signal   => "INT",
+		  cb       => \&ToggleDebug,
+		  data     => "INT");
 
     SetupTimer();
     
@@ -1393,14 +1442,16 @@ sub CreateChild {
     my $host = shift;
     $RemoteHost = $host;
     Log("CRITICAL", "Forking server for ".$host);
-    $pid          = fork;
+    my $pid          = fork;
     if($pid) {			# Parent
-	$ChildHash{$pid} = $RemoteHost;
+	$RemoteHost = "Parent";
+	$ChildHash{$pid} = $host;
+	$HostToPid{$host}= $pid;
 	sigprocmask(SIG_UNBLOCK, $sigset);
 
     } else {			# child.
 	ShowStatus("Connected to ".$RemoteHost);
-	$SIG{INT} = DEFAULT;
+	$SIG{INT} = 'DEFAULT';
 	sigprocmask(SIG_UNBLOCK, $sigset);
 	ChildProcess;		# Does not return.
     }
@@ -1437,11 +1488,13 @@ if ($childpid != 0) {
 #
 
 ShowStatus("Parent writing pid file:");
-$execdir = $perlvar{'lonDaemons'};
+my $execdir = $perlvar{'lonDaemons'};
 open (PIDSAVE, ">$execdir/logs/lonc.pid");
 print PIDSAVE "$$\n";
 close(PIDSAVE);
 
+
+
 if (POSIX::setsid() < 0) {
     print "Could not create new session\n";
     exit -1;
@@ -1451,11 +1504,13 @@ ShowStatus("Forking node servers");
 
 Log("CRITICAL", "--------------- Starting children ---------------");
 
+LondConnection::ReadConfig;               # Read standard config files.
 my $HostIterator = LondConnection::GetHostIterator;
 while (! $HostIterator->end()) {
 
-    $hostentryref = $HostIterator->get();
+    my $hostentryref = $HostIterator->get();
     CreateChild($hostentryref->[0]);
+    $HostHash{$hostentryref->[0]} = $hostentryref->[4];
     $HostIterator->next();
 }
 $RemoteHost = "Parent Server";
@@ -1472,11 +1527,13 @@ $SIG{INT}  = \&Terminate;
 $SIG{TERM} = \&Terminate; 
 $SIG{HUP}  = \&Restart;
 $SIG{USR1} = \&CheckKids; 
+$SIG{USR2} = \&UpdateKids;	# LonManage update request.
 
 while(1) {
-    $deadchild = wait();
+    my $deadchild = wait();
     if(exists $ChildHash{$deadchild}) {	# need to restart.
-	$deadhost = $ChildHash{$deadchild};
+	my $deadhost = $ChildHash{$deadchild};
+	delete($HostToPid{$deadhost});
 	delete($ChildHash{$deadchild});
 	Log("WARNING","Lost child pid= ".$deadchild.
 	      "Connected to host ".$deadhost);
@@ -1506,7 +1563,7 @@ sub CheckKids {
     my $now=time;
     my $local=localtime($now);
     print $fh "LONC status $local - parent $$ \n\n";
-    foreach $pid (keys %ChildHash) {
+    foreach my $pid (keys %ChildHash) {
 	Debug(2, "Sending USR1 -> $pid");
 	kill 'USR1' => $pid;	# Tell Child to report status.
 	sleep 1;		# Wait so file doesn't intermix.
@@ -1515,6 +1572,114 @@ sub CheckKids {
 
 =pod
 
+=head1  UpdateKids
+
+parent's SIGUSR2 handler.  This handler:
+
+=item
+
+Rereads the hosts file.
+
+=item
+ 
+Kills off (via sigint) children for hosts that have disappeared.
+
+=item
+
+QUITs  children for hosts that already exist (this just forces a status display
+and resets the connection retry count for that host.
+
+=item
+
+Starts new children for hosts that have been added to the hosts.tab file since
+the start of the master program and maintains them.
+
+=cut
+
+sub UpdateKids {
+
+    Log("INFO", "Updating connections via SIGUSR2");
+
+    #  Just in case we need to kill our own lonc, we wait a few seconds to
+    #  give it a chance to receive and relay lond's response to the 
+    #  re-init command.
+    #
+
+    sleep(2);			# Wait a couple of seconds.
+
+    my %hosts;                   # Indexed by loncapa hostname, value=ip.
+    
+    # Need to re-read  the host table:
+    
+    
+    LondConnection::ReadConfig();
+    my $I = LondConnection::GetHostIterator;
+    while (! $I->end()) {
+	my $item = $I->get();
+	$hosts{$item->[0]} = $item->[4];
+	$I->next();
+    }
+
+    #  The logic below is written for clarity not for efficiency.
+    #  Since I anticipate that this function is only rarely called, that's
+    #  appropriate.  There are certainly ways to combine the loops below,
+    #  and anyone wishing to obscure the logic is welcome to go for it.
+    #  Note that we don't re-direct sigchild.  Instead we do what's needed
+    #  to the data structures that keep track of children to ensure that
+    #  when sigchild is honored, no new child is born.
+    #
+
+    #  For each existing child; if it's host doesn't exist, kill the child.
+
+    foreach my $child (keys %ChildHash) {
+	my $oldhost = $ChildHash{$child};
+	if (!(exists $hosts{$oldhost})) {
+	    Log("CRITICAL", "Killing child for $oldhost  host no longer exists");
+	    delete $ChildHash{$child};
+	    delete $HostToPid{$oldhost};
+	    kill 'QUIT' => $child;
+	}
+    }
+    # For each remaining existing child; if it's host's ip has changed,
+    # Restart the child on the new IP.
+
+    foreach my $child (keys %ChildHash) {
+	my $oldhost = $ChildHash{$child};
+	my $oldip   = $HostHash{$oldhost};
+	if ($hosts{$oldhost} ne $oldip) {
+
+	    # kill the old child.
+
+	    Log("CRITICAL", "Killing child for $oldhost host ip has changed...");
+	    delete $ChildHash{$child};
+	    delete $HostToPid{$oldhost};
+	    kill 'QUIT' => $child;
+
+	    # Do the book-keeping needed to start a new child on the
+	    # new ip.
+
+	    $HostHash{$oldhost} = $hosts{$oldhost};
+	    CreateChild($oldhost);
+	}
+    }
+    # Finally, for each new host, not in the host hash, create a
+    # enter the host and create a new child.
+    # Force a status display of any existing process.
+
+    foreach my $host (keys %hosts) {
+	if(!(exists $HostHash{$host})) {
+	    Log("INFO", "New host $host discovered in hosts.tab...");
+	    $HostHash{$host} = $hosts{$host};
+	    CreateChild($host);
+	} else {
+	    kill 'HUP' => $HostToPid{$host};    # status display.
+	}
+    }
+}
+
+
+=pod
+
 =head1 Restart
 
 Signal handler for HUP... all children are killed and
@@ -1524,11 +1689,11 @@ the config file.
 =cut
 
 sub Restart {
-    KillThemAll;		# First kill all the children.
+    &KillThemAll;		# First kill all the children.
     Log("CRITICAL", "Restarting");
     my $execdir = $perlvar{'lonDaemons'};
     unlink("$execdir/logs/lonc.pid");
-    exec("$execdir/lonc");
+    exec("$execdir/loncnew");
 }
 
 =pod
@@ -1536,25 +1701,24 @@ sub Restart {
 =head1 KillThemAll
 
 Signal handler that kills all children by sending them a 
-SIGINT.  Responds to sigint and sigterm.
+SIGHUP.  Responds to sigint and sigterm.
 
 =cut
 
 sub KillThemAll {
     Debug(2, "Kill them all!!");
     local($SIG{CHLD}) = 'IGNORE';      # Our children >will< die.
-    foreach $pid (keys %ChildHash) {
+    foreach my $pid (keys %ChildHash) {
 	my $serving = $ChildHash{$pid};
 	Debug(2, "Killing lonc for $serving pid = $pid");
 	ShowStatus("Killing lonc for $serving pid = $pid");
 	Log("CRITICAL", "Killing lonc for $serving pid = $pid");
-	kill('INT', $pid);
-	delete($ChildeHash{$pid});
+	kill 'QUIT' => $pid;
+	delete($ChildHash{$pid});
     }
     my $execdir = $perlvar{'lonDaemons'};
     unlink("$execdir/logs/lonc.pid");
-    ShowStatus("Killing the master process");
-    Log("CRITICAL", "Killing the master process.");
+
 }
 
 =pod
@@ -1567,7 +1731,8 @@ Terminate the system.
 
 sub Terminate {
     KillThemAll;
-    exit;
+    Log("CRITICAL","Master process exiting");
+    exit 0;
 
 }
 =pod