anvil/tools/anvil-safe-start

#!/usr/bin/perl
# 
# This does boot-time sanity checks on nodes and then, if all is well, joins the cluster and boots servers.
# 
# NOTE: Unlike M2, this is controlled by scancore's start, but only if scancore starts up within ten minutes
#       of the node itself booting. This way, stopping/starting scancore won't call us repeatedly. This tool 
#       is enabled or disabled via the 'tool::anvil-safe-start::enabled' variable tied to the 'hosts' -> 
#       'host_uuid' table.
# 
# Exit codes;
# 0 = Normal exit.
# 1 = Any problem that causes an early exit.
# 
# TODO: 
# - Add job support
# - Make this work on DR hosts.
# - 'pcs quorum unblock' could be useful in sole-survivor cold starts.
# - Start DRBD resources if the VMs are running already on the peer.
# 

use strict;
use warnings;
use Anvil::Tools;
use NetAddr::IP;
require POSIX;

my $THIS_FILE           =  ($0 =~ /^.*\/(.*)$/)[0];
my $running_directory   =  ($0 =~ /^(.*?)\/$THIS_FILE$/)[0];
if (($running_directory =~ /^\./) && ($ENV{PWD}))
{
	$running_directory =~ s/^\./$ENV{PWD}/;
}

# Turn off buffering so that the pinwheel will display while waiting for the SSH call(s) to complete.
$| = 1;

my $anvil = Anvil::Tools->new();
$anvil->Log->entry({source => $THIS_FILE, line => __LINE__, 'print' => 1, level => 1, secure => 0, key => "log_0115", variables => { program => $THIS_FILE }});

# Make sure we're running as 'root'
# $< == real UID, $> == effective UID
if (($< != 0) && ($> != 0))
{
	# Not root
	print $anvil->Words->string({key => "error_0005"})."\n";
	$anvil->nice_exit({exit_code => 1});
}

# Connect to the database(s). If we have no connections, we'll proceed anyway as one of the 'run_once' tasks
# is to setup the database server.
$anvil->Database->connect();
$anvil->Log->entry({source => $THIS_FILE, line => __LINE__, level => 2, secure => 0, key => "log_0132"});

$anvil->data->{switches}{'job-uuid'} = "";
$anvil->data->{switches}{disable}    = "";
$anvil->data->{switches}{enable}     = "";
$anvil->data->{switches}{force}      = "";
$anvil->data->{switches}{'local'}    = "";
$anvil->data->{switches}{status}     = "";
$anvil->Get->switches;
$anvil->Log->variables({source => $THIS_FILE, line => __LINE__, level => 2, list => { 
	'switches::job-uuid' => $anvil->data->{switches}{'job-uuid'},
	'switches::disable'  => $anvil->data->{switches}{disable},
	'switches::enable'   => $anvil->data->{switches}{enable},
	'switches::force'    => $anvil->data->{switches}{force},
	'switches::local'    => $anvil->data->{switches}{'local'},
	'switches::status'   => $anvil->data->{switches}{status},
}});

# If I have no databases, sleep until I do
if (not $anvil->data->{sys}{database}{connections})
{
	# If this is a dashboard, try to configure and then connect to the local database. If this isn't a 
	# Wait until we have one.
	$anvil->Log->entry({source => $THIS_FILE, line => __LINE__, 'print' => 1, level => 0, secure => 0, key => "error_0075"});
	
	until($anvil->data->{sys}{database}{connections})
	{
		sleep 10;
		
		$anvil->refresh();
		$anvil->Database->connect();
		$anvil->Log->entry({source => $THIS_FILE, line => __LINE__, level => 3, secure => 0, key => "log_0132"});
		if (not $anvil->data->{sys}{database}{connections})
		{
			# Keep waiting
			$anvil->Log->entry({source => $THIS_FILE, line => __LINE__, 'print' => 0, level => 1, secure => 0, key => "log_0439"});
		}
	}
}

### Process
# 1. Check if I am enabled and that no other copies are running.
# 2. Can I ping my peer on all three networks? Loop until true.
#    - Wait here indefinately
# 3. ...
# 6. Using Start Groups/Delays (and ignoring 'clean' off VMs), boot servers.


# Check to see if we should run. Also checks/sets enable/disable requests.
prerun_checks($anvil);

# Wait until I can ping the peer on all three networks. This will not return until access is available on all
# networks. There is no timeout.
wait_for_access($anvil);

# Start pacemaker now.
start_pacemaker($anvil);

# Boot servers.
boot_servers($anvil);

# Start DRBD resources locally for VMs running on the peer already
check_drbd($anvil);

$anvil->Log->entry({source => $THIS_FILE, line => __LINE__, 'print' => 1, level => 1, key => "job_0281"});

$anvil->nice_exit({exit_code => 0});

#############################################################################################################
# Functions                                                                                                 #
#############################################################################################################

sub check_drbd
{
	my ($anvil) = @_;
	
	# Find the servers running on the peer.
	my $short_host_name      = $anvil->Get->short_host_name();
	my $peer_host_uuid       = $anvil->data->{sys}{peer_host_uuid};
	my $peer_short_host_name = $anvil->data->{hosts}{host_uuid}{$peer_host_uuid}{short_host_name};
	my $peer_password        = $anvil->data->{sys}{peer_password};
	my $peer_ip_address      = $anvil->data->{sys}{peer_target_ip};
	$anvil->Log->variables({source => $THIS_FILE, line => __LINE__, level => 2, list => { 
		short_host_name      => $short_host_name, 
		peer_host_uuid       => $peer_host_uuid, 
		peer_short_host_name => $peer_short_host_name, 
		peer_password        => $anvil->Log->is_secure($peer_password), 
		peer_ip_address      => $peer_ip_address, 
	}});
	
	# Get the list of resources up on the peer.
	$anvil->DRBD->get_status({debug => 2});
	$anvil->DRBD->get_status({
		debug    => 2,
		password => $peer_password,
		target   => $peer_ip_address, 
	});
	
	foreach my $resource (sort {$a cmp $b} keys %{$anvil->data->{drbd}{status}{$peer_ip_address}{resource}})
	{
		foreach my $peer_name (sort {$a cmp $b} keys %{$anvil->data->{drbd}{status}{$peer_ip_address}{resource}{$resource}{connection}})
		{
			my $peer_is_me = $anvil->Network->is_local({host => $peer_name});
			$anvil->Log->variables({source => $THIS_FILE, line => __LINE__, level => 2, list => { 
				peer_host_uuid       => $peer_host_uuid, 
				peer_short_host_name => $peer_short_host_name, 
				peer_password        => $anvil->Log->is_secure($peer_password), 
				peer_ip_address      => $peer_ip_address, 
			}});
			
			my $peer_connection_state  = $anvil->data->{drbd}{status}{$peer_ip_address}{resource}{$resource}{connection}{$peer_name}{'connection-state'};
			my $local_connection_state = exists $anvil->data->{drbd}{status}{$short_host_name}{resource}{$resource}{connection}{$peer_name}{'connection-state'} ? $anvil->data->{drbd}{status}{$short_host_name}{resource}{$resource}{connection}{$peer_name}{'connection-state'} : "";
			$anvil->Log->variables({source => $THIS_FILE, line => __LINE__, level => 2, list => { 
				peer_connection_state  => $peer_connection_state, 
				local_connection_state => $local_connection_state, 
			}});
			
			if (($peer_connection_state =~ /Connecting/i) && ($local_connection_state !~ /StandAlone/i))
			{
				# Start the DRBD resource locally.
				my $return_code = $anvil->DRBD->manage_resource({
					debug    => 2, 
					resource => $resource, 
					task     => "up",
				});
				$anvil->Log->variables({source => $THIS_FILE, line => __LINE__, level => 2, list => { return_code => $return_code }});
			}
		}
	}
	
	return(0);
}

# This boots the servers.
sub boot_servers
{
	my ($anvil) = @_;
	
	# Call 'anvil-boot-server --server all' to boot the servers now.
	$anvil->Log->entry({source => $THIS_FILE, line => __LINE__, 'print' => 1, level => 1, key => "log_0614"});
	my $shell_call = $anvil->data->{path}{exe}{'anvil-boot-server'}." --server all".$anvil->Log->switches;
	$anvil->Log->variables({source => $THIS_FILE, line => __LINE__, level => 2, list => { shell_call => $shell_call }});
	my ($output, $return_code) = $anvil->System->call({shell_call => $shell_call});
	$anvil->Log->variables({source => $THIS_FILE, line => __LINE__, level => 2, list => { 
		output      => $output,
		return_code => $return_code, 
	}});
	if ($return_code)
	{
		# What?! Fail out, we're done.
		$anvil->Log->entry({source => $THIS_FILE, line => __LINE__, 'print' => 1, level => 0, priority => "err", key => "error_0275", variables => {
			output      => $output,
			return_code => $return_code, 
		}});
		$anvil->nice_exit({exit_code => 1});
	}
	
	return(0);
}

# Start pacemaker and wait until we're quorate.
sub start_pacemaker
{
	my ($anvil) = @_;
	
	my $anvil_uuid           = $anvil->data->{sys}{anvil_uuid};
	my $host_uuid            = $anvil->Get->host_uuid();
	my $short_host_name      = $anvil->data->{hosts}{host_uuid}{$host_uuid}{short_host_name};
	my $peer_host_uuid       = $anvil->data->{sys}{peer_host_uuid};
	my $peer_short_host_name = $anvil->data->{hosts}{host_uuid}{$peer_host_uuid}{short_host_name};
	my $fenced_peer          = 0;
	$anvil->Log->variables({source => $THIS_FILE, line => __LINE__, level => 2, list => { 
		anvil_uuid           => $anvil_uuid, 
		host_uuid            => $host_uuid,
		short_host_name      => $short_host_name, 
		peer_host_uuid       => $peer_host_uuid, 
		peer_short_host_name => $peer_short_host_name, 
	}});
	
	# Is pacemaker already running?
	my ($problem) = $anvil->Cluster->parse_cib({debug => 3});
	$anvil->Log->variables({source => $THIS_FILE, line => __LINE__, level => 2, list => { problem => $problem }});
	
	if ($problem)
	{
		# Nope, start it.
		$anvil->Log->entry({source => $THIS_FILE, line => __LINE__, 'print' => 1, level => 1, priority => "alert", key => "log_0608"});
		
		# NOTE: In some odd cases, this can try to run before /etc/hosts has been populated. So wait
		#       until we can access ourself.
		my $ok = 0;
		until ($ok)
		{
			# Convert out short host name to an IP and verify that the IP is one of ours.
			$anvil->Log->entry({source => $THIS_FILE, line => __LINE__, 'print' => 1, level => 1, key => "log_0681"});
			my $local_bcn1_ip = $anvil->Convert->host_name_to_ip({debug => 2, host_name => $short_host_name});
			$anvil->Log->variables({source => $THIS_FILE, line => __LINE__, level => 2, list => { local_bcn1_ip => $local_bcn1_ip }});
			
			if ($local_bcn1_ip)
			{
				# Is this one of our IPs, or is DNS being a little shit?
				if (exists $anvil->data->{network}{$short_host_name})
				{
					delete $anvil->data->{network}{$short_host_name};
				}
				$anvil->Network->get_ips();
				
				foreach my $interface (sort {$a cmp $b} keys %{$anvil->data->{network}{$short_host_name}{interface}})
				{
					next if $anvil->data->{network}{$short_host_name}{interface}{$interface}{ip} eq "";
					next if $anvil->data->{network}{$short_host_name}{interface}{$interface}{ip} =~ /^127\.0\.0\./;
					my $this_ip = $anvil->data->{network}{$short_host_name}{interface}{$interface}{ip};
					$anvil->Log->variables({source => $THIS_FILE, line => __LINE__, level => 2, list => { 
						's1:interface' => $interface,
						's2:this_ip'   => $this_ip, 
					}});
					if ($this_ip eq $local_bcn1_ip)
					{
						$ok = 1;
						$anvil->Log->variables({source => $THIS_FILE, line => __LINE__, level => 2, list => { ok => $ok }});
						last;
					}
				}
			}
			
			if (not $ok)
			{
				# Sleep 10 seconds.
				$anvil->Log->entry({source => $THIS_FILE, line => __LINE__, 'print' => 1, level => 1, priority => "alert", key => "warning_0134"});
				sleep 10;
			}
		}
		
		### TODO: A lot more testing is needed for degraded single-node start later. 
		###       Should we use --all, or wait for our peer? For now, we wait.
		#my $shell_call = $anvil->data->{path}{exe}{pcs}." cluster start --all";
		my $shell_call = $anvil->data->{path}{exe}{pcs}." cluster start";
		$anvil->Log->variables({source => $THIS_FILE, line => __LINE__, level => 2, list => { shell_call => $shell_call }});
		my ($output, $return_code) = $anvil->System->call({shell_call => $shell_call});
		$anvil->Log->variables({source => $THIS_FILE, line => __LINE__, level => 2, list => { 
			output      => $output,
			return_code => $return_code, 
		}});
		if ($return_code)
		{
			# What?! Fail out, we're done.
			$anvil->Log->entry({source => $THIS_FILE, line => __LINE__, 'print' => 1, level => 0, priority => "err", key => "error_0256", variables => {
				output      => $output,
				return_code => $return_code, 
			}});
			$anvil->nice_exit({exit_code => 1});
		}
		
		### TODO: We may implement the logic to fence our peer (similar to cman's post_join_delay' 
		###       logic) at a later time. For now, we'll wait forever for this to exit. This is why
		###       we set 'wait_for_peer', even though it's not used yet.
		# Now wait up to two minutes for the cluster to start. If it's not up by then, we'll fence 
		# the peer and, if the fence succeeds, unblock quorum.
		my $start_time    = time;
		my $wait_for_peer = $start_time + 120;
		my $waiting       = 1;
		$anvil->Log->variables({source => $THIS_FILE, line => __LINE__, level => 2, list => { 
			start_time    => $start_time,
			wait_for_peer => $wait_for_peer, 
		}});
		while ($waiting)
		{
			   $waiting   = 0;
			my ($problem) = $anvil->Cluster->parse_cib({debug => 3});
			$anvil->Log->variables({source => $THIS_FILE, line => __LINE__, level => 2, list => { problem => $problem }});
			if ($problem)
			{
				# Can't parse the CIB yet, wait.
				$waiting = 1;
				$anvil->Log->variables({source => $THIS_FILE, line => __LINE__, level => 2, list => { waiting => $waiting }});
			}
			else
			{
				# Quorum, as reported in the CIB, sets 'have-quorum to '1' as soon as it 
				# starts, the retracts it. For this reason, we use 'parse_quorum()' to get 
				# the quorum directly from corosync/votequorum.
				my ($problem) = $anvil->Cluster->parse_quorum({debug => 2});
				$anvil->Log->variables({source => $THIS_FILE, line => __LINE__, level => 2, list => { problem => $problem }});
				if ($problem)
				{
					# Corosync is down.
					$waiting = 1;
					$anvil->Log->variables({source => $THIS_FILE, line => __LINE__, level => 2, list => { waiting => $waiting }});
				}
				else
				{
					### NOTE: We don't worry about maintenance mode yet, as it shouldn't 
					###       apply, but we may change that view later.
					# See where we are.
					my $node_name        = $anvil->data->{cib}{parsed}{'local'}{name};
					my $maintenance_mode = $anvil->data->{cib}{parsed}{data}{node}{$node_name}{node_state}{'maintenance-mode'};
					my $in_ccm           = $anvil->data->{cib}{parsed}{data}{node}{$node_name}{node_state}{in_ccm};
					my $crmd             = $anvil->data->{cib}{parsed}{data}{node}{$node_name}{node_state}{crmd};
					my $join             = $anvil->data->{cib}{parsed}{data}{node}{$node_name}{node_state}{'join'};
					my $ready            = $anvil->data->{cib}{parsed}{data}{node}{$node_name}{node_state}{ready};
					my $quorate          = $anvil->data->{quorum}{quorate};
					$anvil->Log->variables({source => $THIS_FILE, line => __LINE__, level => 2, list => { 
						's1:node_name'        => $node_name, 
						's2:maintenance_mode' => $maintenance_mode, 
						's3:in_ccm/crmd/join' => $in_ccm."/".$crmd."/".$join,
						's4:ready'            => $ready, 
						's5:quorate'          => $quorate,
					}});
					
					# Are we online?
					if ($ready)
					{
						# We're ready, but do we have quorum?
						if ($quorate)
						{
							$anvil->Log->entry({source => $THIS_FILE, line => __LINE__, 'print' => 1, level => 1, priority => "alert", key => "log_0611", variables => { node_name => $node_name }});
						}
						else
						{
							# Nope
							$waiting = 1;
							$anvil->Log->variables({source => $THIS_FILE, line => __LINE__, level => 2, list => { waiting => $waiting }});
							
							# Keep waiting, or fence the peer?
							if (time > $wait_for_peer)
							{
								### TODO: See above, not implemented yet. Do we want to do this? If so:
								# Time to fence. Use 'pcs stonith fence <peer>', verify it succeeded, 
								# then do 'pcs quorum unblock --force' to finish startup.
							}
							$anvil->Log->entry({source => $THIS_FILE, line => __LINE__, 'print' => 1, level => 1, priority => "alert", key => "log_0610", variables => { node_name => $node_name }});
						}
					}
					else
					{
						# Not ready yet.
						$waiting = 1;
						$anvil->Log->variables({source => $THIS_FILE, line => __LINE__, level => 2, list => { waiting => $waiting }});
						$anvil->Log->entry({source => $THIS_FILE, line => __LINE__, 'print' => 1, level => 1, priority => "alert", key => "log_0612", variables => { 
							node_name => $node_name,
							in_ccm    => $in_ccm,
							crmd      => $crmd,
							'join'    => $join,
						}});
					}
				}
			}
			
			if ($waiting)
			{
				$anvil->Log->entry({source => $THIS_FILE, line => __LINE__, 'print' => 1, level => 1, priority => "alert", key => "log_0609"});
				sleep 5;
			}
		}
	}
	
	return(0);
}

# Check for which networks we have and verify that we can ping our peer on each. This function will not 
# return until all networks are up.
sub wait_for_access
{
	my ($anvil) = @_;
	
	my $host_uuid            = $anvil->Get->host_uuid();
	my $short_host_name      = $anvil->data->{hosts}{host_uuid}{$host_uuid}{short_host_name};
	my $peer_host_uuid       = $anvil->data->{sys}{peer_host_uuid};
	my $peer_short_host_name = $anvil->data->{hosts}{host_uuid}{$peer_host_uuid}{short_host_name};
	my $peer_password        = $anvil->data->{sys}{peer_password};
	$anvil->Log->variables({source => $THIS_FILE, line => __LINE__, level => 2, list => { 
		host_uuid            => $host_uuid,
		short_host_name      => $short_host_name, 
		peer_host_uuid       => $peer_host_uuid, 
		peer_short_host_name => $peer_short_host_name, 
		peer_password        => $anvil->Log->is_secure($peer_password), 
	}});
	
	my $waiting = 1;
	while ($waiting)
	{
		# This will get set back to '1' if 
		$waiting = 0;
		
		# Load IPs (again, to catch changes that might be delaying startup)
		$anvil->Network->load_ips({
			clear     => 1,
			host      => $short_host_name,
			host_uuid => $host_uuid, 
			
		});
		$anvil->Network->load_ips({
			clear     => 1,
			host      => $peer_short_host_name,
			host_uuid => $peer_host_uuid, 
			
		});
		
		# Loop through our interfaces and then loop our peers. Test access over them and set 
		# 'waiting' back to '1' if the connection fails.
		foreach my $interface (sort {$a cmp $b} keys %{$anvil->data->{network}{$short_host_name}{interface}})
		{
			$anvil->Log->variables({source => $THIS_FILE, line => __LINE__, level => 2, list => { 
				interface => $interface,
				waiting   => $waiting, 
			}});
			
			# Only care about our networks.
			next if $waiting;
			if (not $anvil->Network->is_our_interface({interface => $interface}))
			{
				# Not an interface we care about
				next;
			}
			
			my $this_network = ($interface =~ /^(.*?)_/)[0];
			my $ip_address   = $anvil->data->{network}{$short_host_name}{interface}{$interface}{ip};
			my $subnet_mask  = $anvil->data->{network}{$short_host_name}{interface}{$interface}{subnet_mask};
			$anvil->Log->variables({source => $THIS_FILE, line => __LINE__, level => 2, list => { 
				's1:this_network' => $this_network, 
				's2:ip_address'   => $ip_address, 
				's3:subnet_mask'  => $subnet_mask, 
			}});
			
			### NOTE: I know I could match interface names, but that's not certain enough. It's 
			###       possible (if unlikely) that the network name+numbre differs on our peer. So
			###       this is safer.
			# Loop through my peer's interfaces and see if we're sharing this one.
			my $local_network    = NetAddr::IP->new($ip_address."/".$subnet_mask);
			my $peer_match_found = 0;
			foreach my $peer_interface (sort {$a cmp $b} keys %{$anvil->data->{network}{$peer_short_host_name}{interface}})
			{
				last if $peer_match_found;
				my $peer_ip_address  = $anvil->data->{network}{$peer_short_host_name}{interface}{$peer_interface}{ip};
				my $peer_subnet_mask = $anvil->data->{network}{$peer_short_host_name}{interface}{$peer_interface}{subnet_mask};
				$anvil->Log->variables({source => $THIS_FILE, line => __LINE__, level => 2, list => { 
					peer_interface   => $peer_interface, 
					peer_ip_address  => $peer_ip_address, 
					peer_subnet_mask => $peer_subnet_mask, 
				}});
				
				# This the matching network?
				next if $subnet_mask ne $peer_subnet_mask;
				
				my $peer_network = NetAddr::IP->new($peer_ip_address."/".$peer_subnet_mask);
				if ($peer_network->within($local_network))
				{
					# Match, test access.
					   $peer_match_found = 1;
					my $access           = $anvil->Remote->test_access({
						target   => $peer_ip_address,
						password => $peer_password,
					});
					$anvil->Log->variables({source => $THIS_FILE, line => __LINE__, level => 2, list => { access => $access }});
					if ($access)
					{
						# This network is good.
						$anvil->Log->entry({source => $THIS_FILE, line => __LINE__, 'print' => 1, level => 1, key => "log_0604", variables => {
							peer    => $peer_short_host_name, 
							network => $this_network, 
							peer_ip => $peer_ip_address,
						}});
						
						$anvil->data->{sys}{peer_target_ip} = $peer_ip_address;
						$anvil->Log->variables({source => $THIS_FILE, line => __LINE__, level => 2, list => { 
							"sys::peer_target_ip" => $anvil->data->{sys}{peer_target_ip},
						}});
					}
					else
					{
						# No access, wait and try it again.
						$waiting = 1;
						$anvil->Log->entry({source => $THIS_FILE, line => __LINE__, 'print' => 1, level => 1, priority => "alert", key => "log_0605", variables => {
							peer    => $peer_short_host_name, 
							network => $this_network, 
							peer_ip => $peer_ip_address,
						}});
					}
				} 
				
			}
		}
		
		if ($waiting)
		{
			$anvil->Log->entry({source => $THIS_FILE, line => __LINE__, 'print' => 1, level => 1, priority => "alert", key => "log_0606", variables => { peer => $peer_short_host_name }});
			sleep 5;
		}
	}
	
	# All networks are up.
	$anvil->Log->entry({source => $THIS_FILE, line => __LINE__, 'print' => 1, level => 1, priority => "alert", key => "log_0607", variables => { peer => $peer_short_host_name }});
	
	return(0);
}

# This checks to verify that we're a node, and if so, if this tool is enabled. If it's disabled or this isn't
# a node, this method will exit.
sub prerun_checks
{
	my ($anvil) = @_;
	
	$anvil->Database->get_hosts();
	$anvil->Database->get_anvils();
	
	my $host_uuid = $anvil->Get->host_uuid();
	my $host_type = $anvil->data->{hosts}{host_uuid}{$host_uuid}{host_type};
	$anvil->Log->variables({source => $THIS_FILE, line => __LINE__, level => 2, list => { 
		host_uuid => $host_uuid,
		host_type => $host_type, 
	}});
	
	if ($host_type ne "node")
	{
		# We're done.
		$anvil->Log->entry({source => $THIS_FILE, line => __LINE__, 'print' => 1, level => 1, key => "log_0598"});
		$anvil->nice_exit({exit_code => 0});
	}
	
	my $anvil_uuid = $anvil->Cluster->get_anvil_uuid();
	$anvil->Log->variables({source => $THIS_FILE, line => __LINE__, level => 2, list => { anvil_uuid => $anvil_uuid }});
	
	if (not $anvil_uuid)
	{
		# This is a node, but not in an Anvil! yet.
		$anvil->Log->entry({source => $THIS_FILE, line => __LINE__, 'print' => 1, level => 1, key => "log_0603"});
		$anvil->nice_exit({exit_code => 0});
	}
	
	my $node1_host_uuid = $anvil->data->{anvils}{anvil_uuid}{$anvil_uuid}{anvil_node1_host_uuid};
	my $node2_host_uuid = $anvil->data->{anvils}{anvil_uuid}{$anvil_uuid}{anvil_node2_host_uuid};
	$anvil->Log->variables({source => $THIS_FILE, line => __LINE__, level => 2, list => { 
		node1_host_uuid => $node1_host_uuid,
		node2_host_uuid => $node2_host_uuid, 
	}});
	
	$anvil->data->{sys}{anvil_uuid}     = $anvil_uuid;
	$anvil->data->{sys}{peer_host_uuid} = $host_uuid eq $node1_host_uuid ? $node2_host_uuid : $node1_host_uuid;
	$anvil->data->{sys}{peer_password}  = $anvil->data->{anvils}{anvil_uuid}{$anvil_uuid}{anvil_password};
	$anvil->Log->variables({source => $THIS_FILE, line => __LINE__, level => 2, list => { 
		"sys::anvil_uuid"     => $anvil->data->{sys}{anvil_uuid}, 
		"sys::peer_host_uuid" => $anvil->data->{sys}{peer_host_uuid}, 
		"sys::peer_password"  => $anvil->Log->is_secure($anvil->data->{sys}{peer_password}), 
	}});
	
	# Are we being asked to enable or disable? 
	my $nodes   = [$host_uuid];
	my $set_to  = 1;
	my $message = "";
	if ($anvil->data->{switches}{enable})
	{
		# We're enabling, which message will we use?
		$message = $anvil->data->{switches}{'local'} ? "log_0599" : "log_0600";
	}
	elsif ($anvil->data->{switches}{disable})
	{
		# We're disabling. Which message?
		$set_to  = 0;
		$message = $anvil->data->{switches}{'local'} ? "log_0601" : "log_0602";
	}
	
	# If we're updating the settings, do so and then exit.
	if ($message)
	{
		if (not $anvil->data->{switches}{'local'})
		{
			# Add our peer as well.
			push @{$nodes}, $anvil->data->{sys}{peer_host_uuid};
		}
		foreach my $host_uuid (@{$nodes})
		{
			my ($variable_uuid) = $anvil->Database->insert_or_update_variables({
				debug                 => 3,
				variable_name         => "tool::anvil-safe-start::enabled", 
				variable_value        => $set_to, 
				variable_default      => 1, 
				variable_description  => "striker_0286", 
				variable_section      => "system", 
				variable_source_uuid  => $host_uuid, 
				variable_source_table => "hosts", 
			});
			$anvil->Log->variables({source => $THIS_FILE, line => __LINE__, level => 2, list => { variable_uuid => $variable_uuid }});
		}
		
		# Record that it's been enabled.
		$anvil->Log->entry({source => $THIS_FILE, line => __LINE__, 'print' => 1, level => 1, key => $message});
		$anvil->nice_exit({exit_code => 0});
	}
	
	# Read my variables. 
	my ($local_enabled, $variable_uuid, $mtime, $modified_date) = $anvil->Database->read_variable({
		debug                 => 3,
		variable_name         => "tool::anvil-safe-start::enabled", 
		variable_source_table => "hosts", 
		variable_source_uuid  => $host_uuid, 
	});
	$anvil->Log->variables({source => $THIS_FILE, line => __LINE__, level => 2, list => { 
		local_enabled => $local_enabled, 
		variable_uuid => $variable_uuid, 
	}});
	# No UUID means the value hasn't been recorded, so we default to 1.
	if (not $variable_uuid) 
	{
		$local_enabled = 1; 
		$anvil->Log->variables({source => $THIS_FILE, line => __LINE__, level => 2, list => { local_enabled => $local_enabled }});
	}
	
	# Have we just been asked for the status?
	if ($anvil->data->{switches}{status})
	{
		# Yes, check our peer as well.
		my ($peer_enabled, $variable_uuid, $mtime, $modified_date) = $anvil->Database->read_variable({
			debug                 => 3,
			variable_name         => "tool::anvil-safe-start::enabled", 
			variable_source_table => "hosts", 
			variable_source_uuid  => $anvil->data->{sys}{peer_host_uuid}, 
		});
		$anvil->Log->variables({source => $THIS_FILE, line => __LINE__, level => 2, list => { 
			peer_enabled  => $peer_enabled, 
			variable_uuid => $variable_uuid, 
		}});
		# No UUID means the value hasn't been recorded, so we default to 1.
		if (not $variable_uuid) 
		{
			$peer_enabled = 1; 
			$anvil->Log->variables({source => $THIS_FILE, line => __LINE__, level => 2, list => { peer_enabled => $peer_enabled }});
		}
		
		# What we tell the use slightly depends on which nodes are enabled.
		$anvil->Log->variables({source => $THIS_FILE, line => __LINE__, level => 2, list => { 
			local_enabled => $local_enabled, 
			peer_enabled  => $peer_enabled,
		}});
		
		my $message = "";
		if (($local_enabled) && ($peer_enabled))
		{
			# Both nodes are enabled.
			$message = "message_0227";
		}
		elsif ((not $local_enabled) && (not $peer_enabled))
		{
			# Both nodes are disabled
			$message = "message_0228";
		}
		elsif ($local_enabled)
		{
			# We're enabled, the peer is disabled.
			$message = "message_0229";
		}
		else
		{
			# We're disabled, the peer is enabled.
			$message = "message_0230";
		}
		$anvil->Log->entry({source => $THIS_FILE, line => __LINE__, 'print' => 1, level => 1, key => $message});
		$anvil->nice_exit({exit_code => 0});
	}
	
	# Is another instance running?
	my $pids = $anvil->System->pids({
		debug        => 3, 
		ignore_me    => 1,
		program_name => $THIS_FILE,
	});
	my $other_instances = @{$pids};
	$anvil->Log->variables({source => $THIS_FILE, line => __LINE__, level => 2, list => { other_instances => $other_instances }});
	
	if ($other_instances)
	{
		$anvil->Log->entry({source => $THIS_FILE, line => __LINE__, 'print' => 1, level => 1, key => "message_0233"});
		$anvil->nice_exit({exit_code => 0});
	}
	
	# Last test, enabled or forced?
	if (not $local_enabled)
	{
		# Disabled. Forced?
		if ($anvil->data->{switches}{force})
		{
			# Forced, run anyway.
			$anvil->Log->entry({source => $THIS_FILE, line => __LINE__, 'print' => 1, level => 1, key => "message_0232"});
			return(0);
		}
		else
		{
			# Exit.
			$anvil->Log->entry({source => $THIS_FILE, line => __LINE__, 'print' => 1, level => 1, key => "message_0231"});
			$anvil->nice_exit({exit_code => 0});
		}
	}
	
	return(0);
}