#!/usr/bin/perl

###########################################################################
# Author: Vladimir Vuksan http://vuksan.com/linux/
# Collects Disk IO metrics
# Last Changed: $Date: 2007-03-10 14:30:55 -0500 (Sub, 10 Ožu 2007) $
# License: GNU Public License (http://www.gnu.org/copyleft/gpl.html)
# Currently it will collect and send to Ganglia following metrics
# 4 -> reads, 8 -> writes, 12 -> ios IO requests waiting
# If you would like some of the other stats append them 
# below to @which_metrics
###########################################################################
$gmetric_command = "/usr/bin/gmetric";

if ( ! -x $gmetric_command ) {
	die("Gmetric command is not executable. Exiting...");
}

$numArgs = $#ARGV + 1;

if ( $numArgs != 1 ) {
	die("You need to supply device e.g. sda, hda, md0, etc.");
}

$device = $ARGV[0];

@which_metrics = split(/ /, "4 8");

# Where to store the last stats file
$tmp_dir_base="/tmp/disk_stats";
$tmp_stats_file=$tmp_dir_base . "/" . "disk_stats_" . $device;

# Where are the disk stats stored
$proc_file="/proc/diskstats";

###########################################################################
# This is the order of metrics in /proc/diskstats
# 0 major         Major number
# 1 minor         Minor number
# 2 blocks        Blocks
# 3 name          Name
# 4 reads         This is the total number of reads completed successfully.
# 5 merge_read    Reads and writes which are adjacent to each other may be merged for
#               efficiency.  Thus two 4K reads may become one 8K read before it is
#               ultimately handed to the disk, and so it will be counted (and queued)
#               as only one I/O.  This field lets you know how often this was done.
# 6 s_read        This is the total number of sectors read successfully.
# 7 ms_read       This is the total number of milliseconds spent by all reads.
# 8 writes        This is the total number of writes completed successfully.
# 9 merge_write   Reads and writes which are adjacent to each other may be merged for
#               efficiency.  Thus two 4K reads may become one 8K read before it is
#               ultimately handed to the disk, and so it will be counted (and queued)
#               as only one I/O.  This field lets you know how often this was done.
# 10 s_write       This is the total number of sectors written successfully.
# 11 ms_write      This is the total number of milliseconds spent by all writes.
# 12 ios           The only field that should go to zero. Incremented as requests are
#               given to appropriate request_queue_t and decremented as they finish.
# 13 ms_io         This field is increases so long as field 9 is nonzero.
# 14 ms_weighted   This field is incremented at each I/O start, I/O completion, I/O
###########################################################################
%disk_stat = (
	4 => "reads",
	5 => "merge_read",
	6 => "s_read",
	7 => "ms_read",
	8 => "writes",
	9 => "merge_write",
	10 => "s_write",
	11 => "ms_write",
	12 => "ios",
	13 => "ms_io",
	14 => "ms_weighted"
	);

# If the tmp directory doesn't exit create it
if ( ! -d $tmp_dir_base ) {
	system("mkdir -p $tmp_dir_base");
}

###############################################################################
# We need to store a baseline with statistics. If it's not there let's dump 
# it into the file. Don't do anything else
###############################################################################
if ( ! -f $tmp_stats_file ) {
	print "Creating baseline. No output this cycle\n";
	system("cat $proc_file > $tmp_stats_file");
} else {

	# Let's read in the file from the last poll
	open(OLDSTATUS, "< $tmp_stats_file");
	
	while(<OLDSTATUS>)
	{
		my($line) = $_;
		chomp($line);
		@old_stats = split(/ +/,$line);
		if ( $old_stats[3] eq $device ) {
			last;
		}
		undef(@old_stats);
	
	}
	
	close(OLDSTATUS);
	# Get the time stamp when the stats file was last modified
	$old_time = (stat $tmp_stats_file)[9];

	open(NEWSTATUS, "< $proc_file");
	
	while(<NEWSTATUS>)
	{
		my($line) = $_;
		chomp($line);
		@new_stats = split(/ +/,$line);
		if ( $new_stats[3] eq $device ) {
			system("echo '$line' >  $tmp_stats_file");
			last;
		}
		undef(@new_stats);
	}
	
	close(NEWSTATUS);
	$new_time = time(); 

	# Time difference between this poll and the last poll
	my $time_difference = $new_time - $old_time;
	if ( $time_difference < 1 ) {
		die("Time difference can't be less than 1");
	}

	# Calculate deltas and send them to ganglia
	for ( $i = 0 ; $i <= $#which_metrics; $i++ ) {
		$metric = $which_metrics[$i];
		$delta = $new_stats[$metric] - $old_stats[$metric];
		my $rate = int($delta / $time_difference);
	
		if ( $rate < 0 ) {
			print "Something is fishy. Rate for " . $metric . " shouldn't be negative. Perhaps counters were reset. Doing nothing";
		} else {
			print "$disk_stat{$metric} = $rate / sec\n";
			system($gmetric_command . " -tuint16 -u 'calls/sec' -n diskstat_" . $device . "_" . $disk_stat{$metric} . " -v " . $rate);
		}
	}

}

# io requests waiting is not a counter but an absolute value
$metric = 12;
system($gmetric_command . " -tuint16 -u 'ops in queue' -n diskstat_" . $device . "_iowait_queue -v " . $new_stats[$metric]);