#!/usr/local/bin/perl

require "/root/scripts/utils.pl";

####################################### 
$remote_ip = "128.59.172.6";
$local_name = "My";
$remote_name = "Your";
$is_nfs_client = 1;
$from_email = "dl105\@columbia.edu";
####################################### 

# list of recipients to get the alerts via email
$recipient{"systems"} = "systems\@claven.gsb.columbia.edu";
$recipient{"systems-cell"} = "systems-cell\@claven.gsb.columbia.edu";
$recipient{"web-alerts"} = "web-alerts\@claven.gsb.columbia.edu";
$recipient{"web-cell"} = "web-cell\@claven.gsb.columbia.edu";

$iface = "hme0:2";
$ping = "/usr/sbin/ping";

# time in seconds to wait for ping reply
$timeout = 5;

$up_str = "alive";
$command = "$ping $remote_ip $timeout";

$out = `$command`;
if ($out =~ $up_str){
    print "*$remote_name* is up!\n";
}

# the remote machine is down!
else {

    print "*$remote_name* is down!\n";

    # if this machine's courseware 'library' points to the library on
    # the remote machine, thus being a NFS client, the script should 
    # first remove the 'library' symbolic link that's pointing to
    # the remote machine via NFS, since it's no longer available.
    # Then, it should re-create the 'library' symbolic link and point
    # it to the local copy, which is synchronized to the remote copy
    # every 10 minutes.
 
    if ($is_nfs_client == 1){

	# remove link to NFS-mounted 'library' 
	$command = "rm -f /export/home/apache/library";
	print "Command: *$command*\n";
	$out = `$command`;
	
	# point 'library' to a local rsynced copy 'library2'
	$command = "ln -s /export/home/apache/library2 /export/home/apache/library";
	print "Command: *$command*\n";
	$out = `$command`;

    }

    # send out email alerts

    $time_string = `date`;
    @times = split(/[ ]+/, $time_string);
    $time = $times[3];
    $time .= ", ";
    $time .= $times[1];
    $time .= " ";
    $time .= $times[2];

    $subject = "*$local_name* took over *$remote_name*";
    $body .= "*$local_name* has taken over *$remote_name* at $time\n";

    foreach $dest (sort(keys %recipient)){

        print "Sending to $recipient{$dest} ...\n";
        &sendmail($from_email, $recipient{$dest}, $subject, $body);

    }

    # take over the remote machine

    $command = "/sbin/ifconfig $iface $remote_ip netmask 255.255.255.0 up";
    print "Command: *$command*\n";
    $out = `$command`;
}

exit 0;