#!/usr/bin/perl -w
# Plugin to monitor postgres locks.
#
# Copyright Dalibo <cedric.villemain@dalibo.com> 2007
# 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__locks \
#         /etc/munin/plugins/pg_<databasename>_locks
#       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-locks.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.
#
# The config variables need to be write like this :
# [pg_foobase*]
# user foouser
# env.dbname foobase
#
# Magic markers
#%# family=auto
#%# capabilities=autoconf

use strict;
use DBI;
use vars qw ( $debug $configure  );
use constant _PGMINI => 70400;

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 PostgresSQL locks for database $dbname\n";
	print "graph_info Show $dbname Postgresql locks\n";
	print "graph_vlabel Locks\n";
	print "graph_category Postgresql\n";
	print "graph_args --base 1000\n";

  print "accessshare.label Access Share Lock\n";
  print "accessshare.draw LINE\n";
	print "accessshare.type GAUGE\n";
  print "accessshare.min 0\n";
	print "accessshare.info Read only queries\n";

	print "rowshare.label Row Share Lock\n";
  print "rowshare.draw LINE\n";
	print "rowshare.type GAUGE\n";
  print "rowshare.min 0\n";
	print "rowshare.info SELECT FOR SHARE and SELECT FOR UPDATE locks\n";

	print "rowexclusive.label Row Exclusive Lock\n";
  print "rowexclusive.draw LINE\n";
	print "rowexclusive.type GAUGE\n";
  print "rowexclusive.min 0\n";
	print "rowexclusive.info Write queries locks\n";

	print "shareupdateexclusive.label Share Update Exclusive Lock\n";
  print "shareupdateexclusive.draw LINE\n";
	print "shareupdateexclusive.type GAUGE\n";
  print "shareupdateexclusive.min 0\n";
	print "shareupdateexclusive.info VACUUM, ANALYZE, CREATE INDEX CONCURRENTLY.\n";

	print "share.label Share Lock\n";
  print "share.draw LINE\n";
	print "share.type GAUGE\n";
  print "share.min 0\n";
	print "share.info CREATE INDEX.\n";

	print "sharerowexclusive.label Share Row Exclusive Lock\n";
  print "sharerowexclusive.draw LINE\n";
	print "sharerowexclusive.type GAUGE\n";
  print "sharerowexclusive.min 0\n";
	print "sharerowexclusive.info Locks from application.\n";

	print "exclusive.label Exclusive Lock\n";
  print "exclusive.draw LINE\n";
	print "exclusive.type GAUGE\n";
  print "exclusive.min 0\n";
  print "exclusive.info Locks from application or some operation on system catalogs.\n";

	print "accessexclusive.label Access Exclusive Lock\n";
  print "accessexclusive.draw LINE\n";
	print "accessexclusive.type GAUGE\n";
  print "accessexclusive.min 0\n";
	print "accessexclusive.info ALTER TABLE, DROP TABLE, TRUNCATE, REINDEX, CLUSTER, VACUUM FULL, LOCK TABLE.\n";
} else {
  print "# $dsn\n" if $debug;
  my $dbh = DBI->connect ($dsn,
                          $dbuser,
                          $dbpass,
                          {RaiseError =>1});
  unless($dbh) {
    die ("no Unable to access Database $dbname on host $dbhost as user $dbuser.\nError returned was: ". $DBI::errstr."\n");
  }
  my $sql="SELECT mode, count(mode) FROM pg_locks ";
  $sql  .="where database = (select oid from pg_database where datname = ?) ";
  $sql  .="group by mode";
  print "# $sql\n" if $debug;
  my $accessshare          = 0;
  my $rowshare             = 0;
  my $rowexclusive         = 0;
  my $shareupdateexclusive = 0;
  my $share                = 0;
  my $sharerowexclusive    = 0;
  my $exclusive            = 0;
  my $accessexclusive      = 0;
  my $sth = $dbh->prepare ($sql);
  $sth->execute ($dbname);
  printf ("# Rows: %d\n",  $sth->rows) if $debug;
  if ($sth->rows > 0) {
    while (my ($mode, $count) = $sth->fetchrow_array()) {
      if ($mode =~ /accesssharelock/i) {
        $accessshare += $count;
      } elsif ($mode =~ /rowsharelock/i){
        $rowshare += $count;
      } elsif ($mode =~ /rowexclusivelock/i){
        $rowexclusive += $count;
      } elsif ($mode =~ /shareupdateexclusivelock/i){
        $shareupdateexclusive += $count;
      } elsif ($mode =~ /sharelock/i){
        $share += $count;
      } elsif ($mode =~ /sharerowexclusivelock/i){
        $sharerowexclusive += $count;
      } elsif ($mode =~ /exclusivelock/i){
        $exclusive += $count;
      } elsif ($mode =~ /accessexclusivelock/i){
        $accessexclusive += $count;
      }
    }
	}
  print "accessshare.value $accessshare\n";
  print "rowshare.value $rowshare\n";
  print "rowexclusive.value $rowexclusive\n";
  print "shareupdateexclusive.value $shareupdateexclusive\n";
  print "share.value $share\n";
  print "sharerowexclusive.value $sharerowexclusive\n";
  print "exclusive.value $exclusive\n";
  print "accessexclusive.value $accessexclusive\n";
}
exit 0;