#!/usr/bin/perl -w

use POSIX qw(setsid);
use Sys::Syslog;
use Sys::Hostname;
use LWP::Simple;

$debug = 0;
$proc = "pl_mom";
$alias = "pl-mom";

if (! $debug) {
    $kill_thresh = 90;
    $reboot_thresh = 95;
    $log_thresh = 85;
    $change_thresh = 5;
    $min_thresh = 10;

    $sendmail = "/usr/sbin/sendmail -t";
    $pidfile = "/var/run/$proc.pid";
    $rebootfile = "/var/lib/misc/pl_mom.reboot";
} else {
    $kill_thresh = 2;
    $reboot_thresh = 20;
    $log_thresh = 2;
    $change_thresh = 5;
    $min_thresh = 10;

    $sendmail = "cat";
    $pidfile = "./$proc.pid";
    $rebootfile = "./pl_mom.reboot";
}

$sleep = 30;

# daemonize the program
if (! $debug) {
    &daemonize;
}

system("echo $$ > $pidfile");

if (-e $rebootfile) {
    unlink($rebootfile);
    syslog ("warning", "pl_mom: Sending shutdown mail");
    shutdown_mail();
}

my $pid = fork();
if (! $pid) {
    syslog ("info", "pl_mom: Launching reboot kicker");
    reboot_kicker();
    die (0);
}

while (1) {
    $used = int(swap_used());

    if (defined($old_used)) {
	if ($used >= $old_used + $change_thresh) {
	    syslog ("info", "pl_mom: %d%% swap consumed in last %d seconds",
		    $used - $old_used, $sleep);
    	}
    }

    if ($used >= $log_thresh) {
	if (! defined($old_used) || $used != $old_used) {
	    syslog ("info", "pl_mom: Swap used: %d%%", $used);
	}
	get_slice_info();
	my $hog = memory_hog();
	if ($hog) {
	    if ($used < $kill_thresh) {
		if (! defined($Warning{$hog})) {
		    $Warning{$hog} = "sent";
		    syslog ("warning", "pl_mom: Slice $hog is ".
			    "using $Slice{$hog}{mem_pct}%% of memory");
		    #slice_warning_mail($hog);
		}
	    } else {
		syslog ("warning", "pl_mom: Resetting slice $hog");
		if (! $debug) {
		    slice_reset($hog);
		}
		syslog ("warning", "pl_mom: Sending mail to slice $hog");
		slice_reset_mail($hog);
	    }
	}
    }
    
    sleep ($sleep);

    $old_used = $used;
}

sub reboot_kicker {
    while (1) {
	$used = swap_used();

	if ($used >= $reboot_thresh) {
	    syslog ("warning", "pl_mom: Rebooting node");

	    system("touch $rebootfile");
	    if (! $debug) {
		system("shutdown -r now");
	    }
	    die (0);
	}
	
	sleep (1);
    }
}

sub shutdown_mail {
    my $hostname = hostname(); 
    my ($sec, $min, $hour, $mday, $mon, $year, $wday, $yday, $isdat) 
	= localtime(time);
    my $date = sprintf("%4d-%02d-%02d %02d:%02d:%02d", 
		       $year+1900, $mon+1, $mday, $hour, $min, $sec);
    my $to = "To: $alias\@planet-lab.org\n";
    my $from = "From: support\@planet-lab.org\n";
    my $subject = "Subject: $proc rebooted $hostname\n";
    my $msg ="Swap space was exhausted on $hostname and so $proc rebooted ".
	"it.\n\nAs of $date, the node has successfully come back online.\n".
	"\n$date $hostname reboot\n";

    open(SENDMAIL, "|$sendmail") or die "Cannot open $sendmail: $!";
    print SENDMAIL $to;
    print SENDMAIL $from;
    print SENDMAIL $subject;
    print SENDMAIL "Content-type: text/plain\n\n";
    print SENDMAIL $msg;
    close(SENDMAIL);
}

sub slice_reset_mail {
    my $hog = $_[0];
    my $hog_mem = sprintf ("%0.f", $Slice{$hog}{pmem}/1000);
    my $hog_pct = $Slice{$hog}{mem_pct};
    my $hostname = hostname(); 
    my ($sec, $min, $hour, $mday, $mon, $year, $wday, $yday, $isdat) 
	= localtime(time);
    my $date = sprintf("%4d-%02d-%02d %02d:%02d:%02d", 
		       $year+1900, $mon+1, $mday, $hour, $min, $sec);
    my $to = "To: $alias\@planet-lab.org, $hog\@slices.planet-lab.org\n";
    my $from = "From: support\@planet-lab.org\n";
    my $subject = "Subject: $proc resetting slice $hog on $hostname\n";
    my $msg = "As of $date, swap space is nearly exhausted on $hostname.\n\n".
	"Slice $hog is being reset since it is the largest consumer ".
	"of physical memory at ${hog_mem}MB ($hog_pct%).\n\n".
	"Please reply to this message explaining the nature of your ".
	"experiment, and what you are doing to address the problem.\n".
	"\n$date $hostname reset $hog\n";

    open(SENDMAIL, "|$sendmail") or die "Cannot open $sendmail: $!";
    print SENDMAIL $to;
    print SENDMAIL $from;
    print SENDMAIL $subject;
    print SENDMAIL "Content-type: text/plain\n\n";
    print SENDMAIL $msg;
    close(SENDMAIL);
}

sub slice_warning_mail {
    my $hog = $_[0];
    my $hog_mem = sprintf ("%0.f", $Slice{$hog}{pmem}/1000);
    my $hog_pct = $Slice{$hog}{mem_pct};
    my $hostname = hostname(); 
    my ($sec, $min, $hour, $mday, $mon, $year, $wday, $yday, $isdat) 
	= localtime(time);
    my $date = sprintf("%4d-%02d-%02d %02d:%02d:%02d", 
		       $year+1900, $mon+1, $mday, $hour, $min, $sec);

    if ($hog =~ /^root$/) {
	$to = "To: $alias\@planet-lab.org\n";
    } else {
	$to = "To: $alias\@planet-lab.org, $hog\@slices.planet-lab.org\n";
    }	

    my $from = "From: support\@planet-lab.org\n";
    my $subject = "Subject: $proc may reset slice $hog on $hostname\n";
    my $msg = "As of $date, swap space is over $log_thresh% full on ".
	"$hostname.\n\nSlice $hog is the largest consumer ".
	"of physical memory at ${hog_mem}MB ($hog_pct%).\n".
	"Please check the memory usage of your slice to avoid a reset.\n".
	"\n$date $hostname warning $hog\n";

    open(SENDMAIL, "|$sendmail") or die "Cannot open $sendmail: $!";
    print SENDMAIL $to;
    print SENDMAIL $from;
    print SENDMAIL $subject;
    print SENDMAIL "Content-type: text/plain\n\n";
    print SENDMAIL $msg;
    close(SENDMAIL);
}

sub unkillable_alarm_mail {
    my $hog = $_[0];
    my $hog_mem = sprintf ("%0.f", $Slice{$hog}{pmem}/1000);
    my $hog_pct = $Slice{$hog}{mem_pct};
    my $hostname = hostname(); 
    my ($sec, $min, $hour, $mday, $mon, $year, $wday, $yday, $isdat) 
	= localtime(time);
    my $date = sprintf("%4d-%02d-%02d %02d:%02d:%02d", 
		       $year+1900, $mon+1, $mday, $hour, $min, $sec);

    if ($hog =~ /^root$/) {
	$to = "To: $alias\@planet-lab.org\n";
    } else {
	$to = "To: $alias\@planet-lab.org, $hog\@slices.planet-lab.org\n";
    }

    my $from = "From: support\@planet-lab.org\n";
    my $subject = "Subject: $proc: alarm for slice $hog on $hostname\n";
    my $msg = "As of $date, swap space is over $log_thresh% full on ".
	"$hostname.\n\nSlice $hog is the largest consumer ".
	"of physical memory at ${hog_mem}MB ($hog_pct%).\n".
	"The slice will not be reset, but please verify its behavior.\n".
	"\n$date $hostname alarm $hog\n";

    open(SENDMAIL, "|$sendmail") or die "Cannot open $sendmail: $!";
    print SENDMAIL $to;
    print SENDMAIL $from;
    print SENDMAIL $subject;
    print SENDMAIL "Content-type: text/plain\n\n";
    print SENDMAIL $msg;
    close(SENDMAIL);
}

sub slice_reset {
    my $slice = $_[0];
    my $sliceid = $Slice{$slice}{ctx};
    system("chcontext --ctx $sliceid sudo kill -9 -1");
    system("/etc/init.d/vserver-init start $slice");
}

sub swap_used {
    open (SWAP, "</proc/swaps") ||
        die "Cannot open /proc/swaps; $!\n";

    $line = <SWAP>;
    $line = <SWAP>;
    $line =~ s/[\t ]+/ /g;

    my ($filename, $type, $size, $used, $priority) = split(/ /, $line);
    close SWAP;
 
    return 100*($used/$size);
}

sub get_slice_info {
    if (! $debug) {
	$content = get "http://127.0.0.1:3100/slicestat";
    } else {
	$content = `cat ../pl_mom-deploy/slicestat`
    }
    my @lines = split(/\n/, $content);
    %Slice = ();
    foreach $line (@lines) {
	my ($slice, $ctx, $cpu_pct, $mem_pct, $pmem, $vmem, $ntasks) 
	    = split(/,/,$line);
	$Slice{$slice}{ctx} = $ctx;
	$Slice{$slice}{cpu_pct} = $cpu_pct;
	$Slice{$slice}{mem_pct} = $mem_pct;
	$Slice{$slice}{pmem} = $pmem;
	$Slice{$slice}{vmem} = $vmem;
	$Slice{$slice}{ntasks} = $ntasks;
    }
}

sub memory_hog {
    @keys = sort { $Slice{$b}{mem_pct} <=> $Slice{$a}{mem_pct} } (keys %Slice);
    foreach $key (@keys) {
	if ($Slice{$key}{mem_pct} >= $min_thresh) {
	    if ($key =~ /^root$/ || $key =~ /slicestat/ || $key =~ /netflow/) {
		if (! defined ($Warning{$key})) {
		    $Warning{$key} = "sent";
		    syslog ("warning", "pl_mom: Sending alarm mail to ".
			    "unkillable slice $key, using ".
			    "$Slice{$key}{mem_pct}%% of memory");
		    unkillable_alarm_mail($key);
		}
	    } else {
		return $key;
	    }
	} else {
	    #syslog ("info", "pl_mom: No killable slice using > ".
	    #    "$min_thresh%% memory");
	    return;
	}
    }
}

sub daemonize {
    chdir '/'                 or die "Can't chdir to /: $!";
    open STDIN, '/dev/null'   or die "Can't read /dev/null: $!";
    open STDOUT, '>>/dev/null' or die "Can't write to /dev/null: $!";
    open STDERR, '>>/dev/null' or die "Can't write to /dev/null: $!";
    defined(my $pid = fork)   or die "Can't fork: $!";
    exit if $pid;
    setsid                    or die "Can't start a new session: $!";
    umask 0;
}