#!/usr/bin/perl -w

# Sun JVM minor GC statistics.  Parses a verbose log of minor GC
# stats.  Reads the log file and sums time in seconds spent on GC and
# number of times it is performed.  These numbers are saved in a state
# file. The next time the plugin is run it only reads from the point
# it quit the last time and increases the sums based on the lines
# found in the last portion of the log.  Thus we obtain counters.  The
# counters are reset when the log is rotated.

# The two numbers are graphed in _one_ graph.  Where it has been used
# until now these two numbers have been in the same order of
# magnitude.

# Configuration (common with the other sun_jvm_* plugins in this family):
# [jvm_sun_*]
#    env.logfile /var/foo/java.log  (default: /var/log/munin/java.log)
#    env.graphtitle                 (default: "Sun Java")
#    env.grname                     (default: "sun-jvm". Used for state file-name)

# You need to configure your Sun JVM with these options:
# -verbose:gc 
# -Xloggc:/var/log/app/jvm/gc.log
# -XX:+PrintGCTimeStamps
# -XX:+PrintGCDetails

# History: 

# This plugin was developed by various people over some time - no logs
# of this has been found. - In 2006 significant contributions was
# financed by NRK (Norwegian Broadcasting Coproration) and performed
# by Nicolai Langfeldt of Linpro AS in Oslo, Norway.

# $Id: $

use strict;

my $logfile = $ENV{logfile} || "/var/log/app/jvm/gc.log";
my $grtitle = $ENV{graphtitle} || 'Sun Java';
my $grname  = $ENV{graphtitle} || 'sun-jvm';

my $statefile = "/var/lib/munin/plugin-state/plugin-java_sun_${grname}_minorgcs.state";
my $pos   = 0;
my $count = 0;
my $seconds = 0;
my $startsize;
my $timespent;
my $totaltimespent=0;

if ( $ARGV[0] and $ARGV[0] eq "config" ) {
    print "graph_title $grtitle minor GCs pr minute\n";
    print "graph_args --base 1000 -l 0 --rigid\n";
    print "graph_scale no\n";
    print "graph_category virtualization\n";
    print "graph_period minute\n";
    print "gcs.label Number of GCs\n";
    print "gcs.type DERIVE\n";
    print "gcs.min 0\n";
    print "time.label Seconds spent on GC\n";
    print "time.type DERIVE\n";
    print "time.min 0\n";
    exit 0;
}

if (-l $statefile) {
	die("$statefile is a symbolic link, refusing to touch it.");
}

if (! -f $logfile) {
    print "gcs.value U\n";
    print "time.value U\n";
    exit 0;
}

if (-f "$statefile") {
    open (IN, "$statefile") or exit 4;
    ($pos,$count,$timespent) = split(/:/,<IN>);
    close IN;
}

$startsize = (stat $logfile)[7];

if ($startsize < $pos) {
    # Log rotated
    $pos = 0;
}

($pos, $count, $timespent) = parseFile ($logfile, $pos, $count, $timespent);

print "gcs.value $count\n";
print "time.value ",int($timespent),"\n";

open (OUT, ">$statefile") or die "Could not open $statefile for reading: $!\n";
print OUT "$pos:$count:$timespent\n";
close OUT;

sub parseFile {    
    my ($fname, $start, $count, $timespent) = @_;
    my @secs;

    open (LOGFILE, $fname) or die "Could not open $fname: $!\n";

    # Stat filehandle after open - avoids race with logrotater or
    # restart or whatever.

    my $stop = $startsize = (stat LOGFILE)[7];

    if ($startsize < $start) {
	# Log rotated
	$start = 0;
    }

    seek (LOGFILE, $start, 0) or
	die "Could not seek to $start in $fname: $!\n";

    while (tell (LOGFILE) < $stop) {
	my $line =<LOGFILE>;
	chomp ($line);

# Log format: 35.037: [GC 35.038: [DefNew: 166209K->11364K(174080K), 0.2106410 secs] 175274K->26037K(1721472K), 0.2107680 secs]
	if ($line =~ /\[GC.+ (\d+\.\d+) secs\]/) {
	    $count++;
	    $timespent += $1;
	}
    }
    close(LOGFILE);
    return($stop,$count,$timespent);
}

# vim:syntax=perl