#!/usr/bin/perl -w
# Plugin for monitor postgres connections without DBI.
#
# 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__connections \
#         /etc/munin/plugins/pg_<databasename>_connections
#       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/7.4/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;

my $psql   = $ENV{'psql'} || '/usr/bin/psql';
my $dbhost = $ENV{'dbhost'} || '127.0.0.1';
my $dbname = $ENV{'dbname'} || 'template1';
my $dbuser = $ENV{'dbuser'} || 'munin';
#my $dbuserx = $ENV{'dbuserx'} || '';
my $dbport = $ENV{'dbport'} || '5432';
my $dbpass = $ENV{'dbpass'} || 'munin';

my $COMMAND = "PGPASSWORD='$dbpass' '$psql' '$dbname' -h '$dbhost' -U '$dbuser' -p '$dbport' -A -F, -t ";

if (exists $ARGV[0]) {
    if ($ARGV[0] eq "config") {
		my $sqlCommand = "$COMMAND -c 'SHOW max_connections;'";
		my ($max_connections) = `$sqlCommand`;
		my $warning = int ($max_connections * 0.7);
		my $critical = int ($max_connections * 0.8);
		print "graph_title PostgresSQL active connections\n";
		print "graph_args -l 0 --base 1000\n";
		print "graph_vlabel Connections\n";
		print "graph_category db\n";
		print "graph_info Shows active Postgresql connections from $dbname\n";


		$sqlCommand = "$COMMAND -c 'select datname, count(*) from pg_stat_activity group by datname;'";
		open(SERVICE, "$sqlCommand |")
			or die("Could not execute '$sqlCommand': $!");

		my $setarea = "yes";
		while (<SERVICE>) {
			my ($datname, $curr_conn) = (m/(\w+).*?(\d+(?:\.\d+)?)/);

			print "$datname.label $datname active connections\n";
			print "$datname.info $datname active connections\n";
			print "$datname.type GAUGE\n";
			if ($setarea eq "yes") {
        		print "$datname.draw AREA\n";
				$setarea="";
        	} else {
				print "$datname.draw STACK\n";
			}
		}

		print "max_connections.label Max. connections\n";
		print "max_connections.info Max. connections\n";
		print "max_connections.type GAUGE\n";

		print "warning $warning\n";
		print "critical $critical\n";
		exit 0;
    }
}

# select datname, count(*) from pg_stat_activity group by datname
my $sqlCommand = "$COMMAND -c 'SHOW max_connections;'";
my ($max_connections) = `$sqlCommand`;

$sqlCommand = "$COMMAND -c 'select datname, count(*) from pg_stat_activity group by datname;'";
open(SERVICE, "$sqlCommand |")
	or die("Could not execute '$sqlCommand': $!");

while (<SERVICE>) {
	my ($datname, $curr_conn) = (m/(\w+).*?(\d+(?:\.\d+)?)/);
	print "$datname.value $curr_conn\n";
}
print "max_connections.value $max_connections\n";