Find the total size of largest tables (#155)

* Find the total size of largest tables

* update changelog

* appease the cops

Co-authored-by: Ben Abrams <me@benabrams.it>

Author: phumpal

CHANGELOG.md

@@ -4,6 +4,8 @@ This project adheres to [Semantic Versioning](http://semver.org/).
 This CHANGELOG follows the format listed [here](https://github.com/sensu-plugins/community/blob/master/HOW_WE_CHANGELOG.md).
 
 ## [Unreleased]
+### Added
+- new `bin/metric-postgres-relation-size.rb` find largest tables (@phumpal)
 
 ## [4.1.0] - 2020-06-04
 ### Added

README.md

@@ -22,6 +22,7 @@
  * bin/metric-postgres-statsio.rb
  * bin/check-postgres-query.rb
  * bin/metrics-postgres-query.rb
+ * bin/metric-postgres-relation-size.rb
 
 ## Usage
 

bin/metric-postgres-relation-size.rb

@@ -0,0 +1,118 @@
+#! /usr/bin/env ruby
+# frozen_string_literal: false
+
+#  metrics-postgres-relation-size.rb
+# DESCRIPTION:
+#
+#   This plugin finds the total size of the largest tables.
+#
+#   https://www.postgresql.org/docs/current/functions-admin.html#FUNCTIONS-ADMIN-DBOBJECT
+#
+# OUTPUT:
+#   metric data
+#
+# PLATFORMS:
+#   Linux
+#
+# DEPENDENCIES:
+#   gem: sensu-plugin
+#   gem: pg
+#
+# USAGE:
+#   ./metric-postgres-relation-size.rb -u db_user -p db_pass -h db_host -d db
+#
+# NOTES:
+#
+# LICENSE:
+#   Copyright (c) 2020 Airbrake Technologies, Inc <support@airbrake.io>
+#   Author Patrick Humpal <patrick@netvilla.net>
+#   Released under the same terms as Sensu (the MIT license); see LICENSE
+#   for details.
+#
+
+require 'sensu-plugins-postgres/pgpass'
+require 'sensu-plugin/metric/cli'
+require 'pg'
+require 'socket'
+
+class PostgresStatsDBMetrics < Sensu::Plugin::Metric::CLI::Graphite
+  option :pgpass,
+         description: 'Pgpass file',
+         short: '-f FILE',
+         long: '--pgpass',
+         default: ENV['PGPASSFILE'] || "#{ENV['HOME']}/.pgpass"
+
+  option :user,
+         description: 'Postgres User',
+         short: '-u USER',
+         long: '--user USER'
+
+  option :password,
+         description: 'Postgres Password',
+         short: '-p PASS',
+         long: '--password PASS'
+
+  option :hostname,
+         description: 'Hostname to login to',
+         short: '-h HOST',
+         long: '--hostname HOST'
+
+  option :port,
+         description: 'Database port',
+         short: '-P PORT',
+         long: '--port PORT'
+
+  option :database,
+         description: 'Database name',
+         short: '-d DB',
+         long: '--db DB'
+
+  option :scheme,
+         description: 'Metric naming scheme, text to prepend to $queue_name.$metric',
+         long: '--scheme SCHEME',
+         default: "#{Socket.gethostname}.postgresql"
+
+  option :timeout,
+         description: 'Connection timeout (seconds)',
+         short: '-T TIMEOUT',
+         long: '--timeout TIMEOUT',
+         default: nil
+
+  option :limit,
+         description: 'Limit query to this many results',
+         short: '-L LIMIT',
+         login: '--limit LIMIT',
+         default: 25
+
+  include Pgpass
+
+  def run
+    timestamp = Time.now.to_i
+    pgpass
+    con = PG.connect(host: config[:hostname],
+                     dbname: config[:database],
+                     user: config[:user],
+                     password: config[:password],
+                     port: config[:port],
+                     connect_timeout: config[:timeout])
+
+    # https://wiki.postgresql.org/wiki/Disk_Usage
+    request = [
+      "SELECT nspname || '.' || relname AS relation,
+       pg_total_relation_size(C.oid) AS total_size
+       FROM pg_class C
+       LEFT JOIN pg_namespace N on (N.oid = C.relnamespace)
+       WHERE nspname NOT IN ('pg_catalog', 'information_schema')
+       ORDER BY pg_total_relation_size(C.oid) DESC
+       LIMIT '#{config[:limit]}'"
+    ]
+
+    con.exec(request.join(' ')) do |result|
+      result.each do |row|
+        output "#{config[:scheme]}.size.#{config[:database]}.#{row['relation']}", row['total_size'], timestamp
+      end
+    end
+
+    ok
+  end
+end