#!/usr/bin/perl -w
# -*- perl -*-

=head1 NAME

docker_cpu - Munin plugin to monitor docker container CPU usage.

=head1 APPLICABLE SYSTEMS

Should work on any Linux system that has docker support.

=head1 CONFIGURATION

Root privilege required to execute docker command.

1. Create a new file named "docker" inside the folder /etc/munin/plugin-conf.d/
2. Docker file content:

[docker_cpu]
user root

=head1 MAGIC MARKERS

  #%# family=auto
  #%# capabilities=autoconf

=head1 VERSION

  v.0.1

=head1 AUTHOR

Copyright (C) 2015 Samuel Cantero.
Email: scanterog at gmail dot com

=head1 LICENSE

GPLv3

=cut

my $docker=`which docker`;

if ( defined $ARGV[0] and $ARGV[0] eq "autoconf" ) {
   if ($docker) {
      print "yes\n";
      exit 0;
   }
   else{
      print "no (Docker has not been found)\n";
      exit 0;
   }
}

$docker =~ s/\s+$//;

my @containers = split "\n" , `$docker ps --no-trunc=true`;
my $result;

for my $i (1 .. $#containers)
{
   my @fields = split / +/, $containers[$i];
   my $id = $fields[0];
   my $name = $fields[$#fields];
   # manage container name containing arithmetic operators and dots. E.g, my-container.
   $name =~ s/[-\+*\/\.]/_/g;
   # truncate container name with "," character.
   $name =~ s/,.*//g;
   if (open(my $file, '<', "/sys/fs/cgroup/cpuacct/docker/$id/cpuacct.usage"))
   {
      my $total_cpu_ns = <$file>;
      $total_cpu_ns =~ s/\s+$//;
      close $file;
      if (open($file, '<', "/sys/fs/cgroup/cpuacct/docker/$id/cpuacct.usage_percpu"))
      {
         my @ncpu = split / /, <$file>;
         close $file;
         push @result, {'name'=>$name, 'total_cpu_ns'=>$total_cpu_ns, 'ncpu'=>$#ncpu};
      }
   }
}
 
if (defined $ARGV[0] and $ARGV[0] eq "config")
{
   my $nanoSecondsInSecond=1000000000;
   my $graphlimit = $result[0]{'ncpu'};
   foreach(@result){
      if ($$_{'ncpu'} > $graphlimit){
         $graphlimit = $$_{'ncpu'};
      }
   } 
   $graphlimit = $graphlimit * 100;
   print "graph_title Docker container CPU usage\n";
   print "graph_args --base 1000 -r --lower-limit 0 --upper-limit $graphlimit\n";
   print "graph_vlabel %\n";
   print "graph_scale no\n";
   print "graph_period second\n";
   print "graph_category virtualization\n";
   print "graph_info This graph shows docker container CPU usage.\n";
   
   foreach(@result)
   {
      print "$$_{'name'}.label $$_{'name'}\n";
      print "$$_{'name'}.draw LINE2\n";
      print "$$_{'name'}.min 0\n";
      print "$$_{'name'}.type DERIVE\n";
      print "$$_{'name'}.cdef $$_{'name'},$nanoSecondsInSecond,/\n";
   }
   exit 0;
}

# Note: Counters/derive need to report integer values.

foreach(@result)
{
   $tcpu = ($$_{'total_cpu_ns'}*100); #to percentage
   print "$$_{'name'}.value $tcpu\n";
}

# vim:syntax=perl