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contrib-munin/plugins/other/postgres_block_read_

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2006-10-12 14:45:20 +02:00
#!/usr/bin/perl
# Plugin to monitor Postgresql memory usage; gives number of blocks
# read from disk and from memory, showing how much of the database is
# served from Postgresql's memory buffer.
#
# PLEASE NOTE: This plugin may not present the whole truth - the truth
# may actually be even better than this plugin will show you! That is
# because Postgresql statistics only considers memory block reads from
# its own allocated memory. When Postgresql reads from disk, it may
# actually still be read from memory, but from the _kernel_'s
# memory. Summarily, your database server may run even better than
# this plugin will indicate. See
# http://www.postgresql.org/docs/7.4/interactive/monitoring-stats.html
# for a (short) description.
#
# Copyright Bj<42>rn Ruberg <bjorn@linpro.no> 2006
#
# 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/postgres_block_read_ \
# /etc/munin/plugins/postgres_block_read_SomeDatabase
# 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'.
# 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 suggest
use strict;
use DBI;
use Data::Dumper;
use vars qw ( $debug $suggest $configure $dbh );
# Need these variables at an early stage to enable
# autoconf and suggest
my $dbhost = $ENV{'dbhost'} || ''; # Connect to localhost by default
my $dbname = $ENV{'dbname'} || 'template1';
my $dbuser = $ENV{'dbuser'} || 'postgres';
my $dbpass = $ENV{'dbpass'} || '';
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;
}
# Then we try to detect Postgres presence by connecting to
# 'template1'.
my $dsn = "dbi:Pg:dbname=template1";
$dsn .= ";host=$dbhost" if $dbhost;
my $tempdbh = DBI->connect ($dsn, $dbuser, $dbpass);
if ($tempdbh) {
print "yes\n";
exit 0;
} else {
print "no (Can't connect to given host, please check environment settings)\n";
exit 1;
}
} elsif ($ARGV[0] eq 'debug') {
# Set debug flag
$debug = 1;
} elsif ($ARGV[0] eq 'config') {
# Set config flag
$configure = 1;
} elsif ($ARGV[0] eq 'suggest') {
# doesn't always work
my @datasources = DBI->data_sources ('Pg');
foreach my $dsn (grep !/\=template\d$/, @datasources) {
(my $db = $dsn) =~ s/^.*=//;
print "$db\n";
}
exit 0;
}
}
# Must do this here, after checking for autoconf/suggest/etc, because the
# plugin must be able to run before it is linked to the databases.
my (undef, undef, undef, $dbname) = split (/_/, $0, 4);
die "No dbname configured (did you make the proper symlink?)" unless $dbname;
my @datasources = DBI->data_sources ('Pg')
or die ("Can't read any possible data sources: $?");
my $dsn = "DBI:Pg:dbname=$dbname";
$dsn .= ";host=$dbhost" if $dbhost;
print "#$dsn\n" if $debug;
my $dbh = DBI->connect ($dsn, $dbuser, $dbpass, {RaiseError =>1});
unless($dbh) {
die("Database $dbname\@$dbhost (". $DBI::errstr .")\n");
}
if ($configure) {
print <<EOF;
graph_title Postgres data reads from $dbname
graph_args --base 1000
graph_vlabel Blocks read per \${graph_period}
graph_category Postgresql
graph_info Shows number of blocks read from disk and from memory
from_disk.label Read from disk
from_disk.info Read from disk
from_disk.type DERIVE
from_disk.min 0
from_disk.draw AREA
from_memory.label Cached in memory
from_memory.info Cached in memory
from_memory.type DERIVE
from_memory.min 0
from_memory.draw STACK
EOF
} else {
my $sql = "SELECT (SUM (heap_blks_read) + SUM (idx_blks_read) + ";
$sql .= "SUM (toast_blks_read) + SUM (tidx_blks_read)) AS disk, ";
$sql .= "(SUM (heap_blks_hit) +SUM (idx_blks_hit) + ";
$sql .= "SUM (toast_blks_hit) + SUM (tidx_blks_hit)) AS mem ";
$sql .= "from pg_statio_user_tables ";
print "# $sql\n" if $debug;
my $sth = $dbh->prepare ($sql);
$sth->execute();
if ($sth->rows > 0) {
printf ("# Rows: %d\n", $sth->rows) if $debug;
my ($disk, $mem) = $sth->fetchrow_array();
print "from_disk.value $disk\n";
print "from_memory.value $mem\n";
}
}