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

=head1 NAME

docker_memory - Munin plugin to monitor docker container memory 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_memory]
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 $file, '<', "/sys/fs/cgroup/memory/docker/$id/memory.usage_in_bytes"))
   {
      my $memory_bytes = <$file>;
      $memory_bytes =~ s/\s+$//;
      push @result, {'name'=>$name, 'memory_bytes'=>$memory_bytes};
   }
}

if (defined $ARGV[0] and $ARGV[0] eq "config")
{
   print "graph_title Docker container memory usage\n";
   print "graph_args --base 1024 -l 0\n";
   print "graph_vlabel Bytes\n";
   print "graph_category virtualization\n";
   print "graph_info This graph shows docker container memory usage.\n";
   
   foreach(@result)
   {
      print "$$_{'name'}.label $$_{'name'}\n";
      print "$$_{'name'}.draw LINE2\n";
   }
   exit 0;
}

foreach(@result)
{
   print "$$_{'name'}.value $$_{'memory_bytes'}\n";
}

# vim:syntax=perl