#!/usr/bin/perl -w
# Plugin to monitor pg_stat_bgwriter
#
# Copyright Dalibo <cedric.villemain@dalibo.com> 2008
# Based on a plugin (postgres_block_read_) from Björn Ruberg <bjorn@linpro.no>
#
# Licenced under GPL v2.
#
# Usage:
#
#       Symlink into /etc/munin/plugins/ and add the monitored
#       database to the filename. e.g.:
#
#       ln -s /usr/share/munin/plugins/pg__stat_bgwriter \
#         /etc/munin/plugins/pg_<databasename>_stat_bgwriter
#       This should, however, be given through autoconf and suggest.
#
#       If required, give username, password and/or Postgresql server
#       host through environment variables.
#
#       You must also activate Postgresql statistics. See
#       http://www.postgresql.org/docs/8.1/interactive/monitoring-stats.html
#       for how to enable this. Specifically, the following lines must
#       exist in your postgresql.conf:
#
#           stats_start_collector = true
#           stats_block_level = true
#
#
# Parameters:
#
#       config   (required)
#
# Config variables:
#
#       dbhost     - Which database server to use. Defaults to
#                    'localhost'.
#       dbname     - Which database to use. Defaults to template1
#       dbuser     - A Postgresql user account with read permission to
#                    the given database. Defaults to
#                    'postgres'. Anyway, Munin must be told which user
#                    this plugin should be run as.
#       dbpass     - The corresponding password, if
#                    applicable. Default to undef. Remember that
#                    pg_hba.conf must be configured accordingly.
#
# Magic markers
#%# family=auto
#%# capabilities=autoconf

use strict;
use DBI;
use vars qw ( $debug $configure  );
use constant _PGMINI => 80300;

my $dbhost = $ENV{'dbhost'} || '';
my $dbname = $ENV{'dbname'} || 'template1';
my $dbuser = $ENV{'dbuser'} || 'postgres';
my $dbport = $ENV{'dbport'} || '5432';
my $dbpass = $ENV{'dbpass'} || '';
my $statscope = $ENV{'statscope'} || 'user';

my $dsn = "DBI:Pg:dbname=$dbname";
$dsn   .=";host=$dbhost;port=$dbport" if $dbhost;
my $pg_server_version;

if (exists $ARGV[0]) {
  if ($ARGV[0] eq 'autoconf') {
    # Check for DBD::Pg
    if (! eval "require DBD::Pg;") {
      print "no (DBD::Pg not found)";
      exit 1;
    }
    my $dbh = DBI->connect ($dsn,
                            $dbuser,
                            $dbpass,
                            {RaiseError =>1});
    if ($dbh) {
      $pg_server_version = $dbh->{'pg_server_version'};
      if ($pg_server_version < (_PGMINI)) {
        $pg_server_version =~ /(\d)(\d){2,2}(\d){2,2}/;
        print "PostgreSQL Server version " . (_PGMINI) . " or above is needed. Current is $1.$2.$3 \n";
				exit 1;
      }
      print "yes\n";
      exit 0;
    } else {
      print "no Unable to access Database $dbname on host $dbhost as user $dbuser.\nError returned was: ". $DBI::errstr;
      exit 1;
    }
  } elsif ($ARGV[0] eq 'debug') {
    # Set debug flag
    $debug = 1;
  } elsif ($ARGV[0] eq 'config') {
    # Set config flag
    $configure = 1;
  }
}

if ($configure) {
  print "graph_title PostgreSQL stat bgwriter\n";
  print "graph_vlabel Number / \${graph_period}\n";
  print "graph_category Postgresql \n";
  print "graph_args --base 1000\n";

  print "checkpoints_timed.label Checkpoints issued because of checkpoint_timeout\n";
  print "checkpoints_timed.draw LINE\n";
  print "checkpoints_timed.type DERIVE\n";
  print "checkpoints_timed.min 0\n";
  print "checkpoints_timed.graph_info Number of scheduled checkpoints\n";

  print "checkpoints_req.label Checkpoint issued by request\n";
  print "checkpoints_req.draw LINE\n";
  print "checkpoints_req.type DERIVE\n";
  print "checkpoints_req.min 0\n";
  print "checkpoints_req.graph_info Number of requested checkpoint\n";

  print "buffers_checkpoint.label Buffers write when checkpoint occured\n";
  print "buffers_checkpoint.draw LINE\n";
  print "buffers_checkpoint.type DERIVE\n";
  print "buffers_checkpoint.min 0\n";
  print "buffers_checkpoint.graph_info Number of buffers written when checkpoint \n";

  print "buffers_clean.label Buffers write for cleaning\n";
  print "buffers_clean.draw LINE\n";
  print "buffers_clean.type DERIVE\n";
  print "buffers_clean.min 0\n";
  print "buffers_clean.graph_info Number of buffers written when cleaning\n";

  print "maxwritten_clean.label Times cleaning scan is stopped because exceed bgwriter_lru_maxpages\n";
  print "maxwritten_clean.draw LINE\n";
  print "maxwritten_clean.type DERIVE\n";
  print "maxwritten_clean.min 0\n";
  print "maxwritten_clean.graph_info Number of stop in cleaning\n";

  print "buffers_backend.label Number of buffers written by backends\n";
  print "buffers_backend.draw LINE\n";
  print "buffers_backend.type DERIVE\n";
  print "buffers_backend.min 0\n";
  print "buffers_backend.graph_info Number of buffers written by backends\n";

  print "buffers_alloc.label Total number of buffers allocated\n";
  print "buffers_alloc.draw LINE\n";
  print "buffers_alloc.type DERIVE\n";
  print "buffers_alloc.min 0\n";
  print "buffers_alloc.graph_info Total number of buffers allocated\n";
} else {
  print "# $dsn\n" if $debug;
  my $dbh = DBI->connect ($dsn,
                          $dbuser,
                          $dbpass,
                          {RaiseError =>1});
  die ("no Unable to access Database $dbname on host $dbhost as user $dbuser.\nError returned was: ". $DBI::errstr."\n")
  	unless($dbh);
  $pg_server_version = $dbh->{'pg_server_version'};

  my $sql = "select checkpoints_timed, checkpoints_req, ";
  $sql 	 .= "       buffers_checkpoint, buffers_clean, ";
  $sql 	 .= "       maxwritten_clean, buffers_backend, ";
  $sql 	 .= "       buffers_alloc ";
  $sql 	 .= "from pg_stat_bgwriter;";
  print "# $sql\n" if $debug;
  my $sth = $dbh->prepare($sql);
  $sth->execute();
  printf ("# Rows: %d\n",  $sth->rows) if $debug;
  if ($sth->rows > 0) {
    my ($checkpoints_timed, $checkpoints_req, $buffers_checkpoint, $buffers_clean, $maxwritten_clean, $buffers_backend, $buffers_alloc) = $sth->fetchrow_array();
    print "checkpoints_timed.value $checkpoints_timed\n";
    print "checkpoints_req.value $checkpoints_req\n";
    print "buffers_checkpoint.value $buffers_checkpoint\n";
    print "buffers_clean.value $buffers_clean\n";
    print "maxwritten_clean.value $maxwritten_clean\n";
    print "buffers_backend.value $buffers_backend\n";
    print "buffers_alloc.value $buffers_alloc\n";
	}
}

exit 0;