Initial version

plugins/other/postgres_block_read_

@@ -0,0 +1,159 @@
+#!/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 Bjørn 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";
+    }
+}