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File name : standby

Content :

#!/usr/bin/perl

# dh2 standby script (for failover)
#
# invoke upon entry into runlevel 2.  checks logical identity (defined
# in /dh/etc/logical-identity) to see if it's up.  if not (ie no other
# machine has taken over in its stead) switches to runlevel 3, which
# assumes that persona, starts services, etc.
#
# if logical identity is already up (taken over), standby exits and 
# machine remains in runlevel 2.

use strict;
use Sys::Syslog qw(:DEFAULT setlogsock);

my $verbose = 1;
my $ping = "ping -n -q";
my $logical_runlevel = 2;
my $standby_runlevel = 4;

my $command = shift @ARGV;

setlogsock 'unix';
openlog 'standby', 'pid', 'daemon';

sub my_syslog {
	eval {
		local $SIG{"__DIE__"}= sub { };
		Sys::Syslog::syslog(@_);
	}
}

sub p($) {
	my $p = shift;
	print "standby: $p";
	my_syslog 'info', $p;
}

sub d($) {
	my $p = shift;
	p $p;
	exit 1;
}

# background!
#if (fork()) {
#	print "Backgrounding dh2 standby agent with 5 second delay.\n";
#	exit 0;
#}

p "[-- dh2 standby agent --]\n";

#p "sleeping 5 seconds for init to chill out\n";
#sleep 5;

if ($command eq 'start') {
	# load physical identity
	open(I,"/etc/network/physical-identity") || d "missing /etc/network/physical-identity\n";
	my $pip = ;
	my $phost = ;
	my $pfqdn = ;
	my $rl = ;
	close I;
	chomp($pip);
	chomp($phost);
	chomp($pfqdn);
	chomp($rl);
	$standby_runlevel = $rl if $rl;

unless ($pip) {
		d "No physical node, not doing anything.";
		exit 0;
	}
	p "Physical node: $phost ($pfqdn), $pip, standby runlevel $standby_runlevel\n" if $verbose;
	
	# load logical identity
	open(I,"/etc/network/logical-identity") || d "missing /etc/network/logical-identity\n";
	my $lip = ;
	my $lhost = ;
	my $lfqdn = ;
	my $lrl = ;
	close I;
	chomp($lip);
	chomp($lhost);
	chomp($lfqdn);
	chomp($lrl);
	$logical_runlevel = $lrl if $lrl;

unless ($lip) {
		d "No logical node, not doing anything.\n";
		exit 0;
	}

p "Logical node: $lhost ($lfqdn), $lip, runlevel $logical_runlevel\n" if $verbose;

# did we boot?
	my ($lastrunlevel, $currunlevel) = split(/\s+/,`runlevel`);
	p "Runlevel $lastrunlevel -> $currunlevel\n";

if ($currunlevel != $standby_runlevel) {
		d "not in standby runlevel ($standby_runlevel) , not doing anything\n";
	}

if ($lastrunlevel eq 'N') {
		
		# ping logical host
		my $count = 10;
		p "Just booted!  Pinging $lip (count $count) ...\n";
#		my $r = system "$ping -c $count $lip > /dev/null";
#		my $r = 1;
		my $out = `$ping -c $count $lip`;
		my $r = $out =~ / 0 received/;
		if ($r) {
			# unreachable!
			p "$lip unreachable!  switching to runlevel $logical_runlevel\n";
			system "telinit $logical_runlevel > /dev/null";
		} elsif ($out =~ / packets received/) {
			p "$lip reachable!  we've been taken over, reamining in this runlevel.\n";
		} else {
			p "ping died!  something's funny, remaining in this runlevel.\n";
		}
	} else {
		p "we just boot, not doing anything.\n";
	}
}