#!/usr/bin/perl -w

if ($#ARGV != 0) {
	print "Usage: throttle <pid>\n";
	exit 1;
}

$pid = $ARGV[0];
$threshold = 1800;

# Get status
open STAT, "/proc/$pid/stat" or die "No such process $pid\n";
@bits = split(/ /, <STAT>);
$state = $bits[2];
close STAT;

print "Found process, state=$state";

if ($state eq 'T') {
	print " (not running)\n";
	$running = 0;
} else {
	print " (running)\n";
	$running = 1;
}

# Monitor albert's NFS traffic stats and continue when the calls per second drops below $threshold
$alive = 1;
while ($alive) {
	$traffic = `ganglia-fetch -h albert -p 8662 albert.wikimedia.org nfs_server_calls`;
	chomp($traffic);
	
	if ($running) {
		if ($traffic > $threshold) {
			print "nfs_server_calls = $traffic, stopping\n";
			$alive = kill SIGSTOP, $pid;
			$running = 0;
		}
	} else {
		if ($traffic < $threshold) {
			print "nfs_server_calls = $traffic, starting\n";
			$alive = kill SIGCONT, $pid;
			$running = 1;
		}
	}
	sleep 10;
}