Monitor dead tuples per table

Gemfile.lock

+PATH
+  remote: .
+  specs:
+    gitlab-monitor (0.0.1)
+      pg (~> 0.18.4)
+
 GEM
   remote: https://rubygems.org/
   specs:
@@ -5,6 +11,7 @@ GEM
     diff-lcs (1.2.5)
     parser (2.3.1.2)
       ast (~> 2.2)
+    pg (0.18.4)
     powerpack (0.1.1)
     rainbow (2.1.0)
     rspec (3.5.0)
@@ -33,6 +40,7 @@ PLATFORMS
   ruby
 
 DEPENDENCIES
+  gitlab-monitor!
   rspec (~> 3.5)
   rubocop (~> 0.42)
 

bin/gitlab-mon

 #!/usr/bin/env ruby
 
+$LOAD_PATH.unshift File.expand_path("../../lib", __FILE__)
+
 require "optparse"
 require "gitlab_monitor"
 

gitlab-monitor.gemspec

@@ -20,5 +20,7 @@ Gem::Specification.new do |s|
   s.homepage      = "http://gitlab.com"
   s.license       = "MIT"
 
+  s.add_runtime_dependency "pg", "~> 0.18.4"
+
   s.add_development_dependency "rspec", "~> 3.3"
 end

lib/gitlab_monitor.rb

@@ -6,5 +6,6 @@ module GitLab
     autoload :PrometheusMetrics, "gitlab_monitor/prometheus"
     autoload :Git,               "gitlab_monitor/git"
     autoload :GitProber,         "gitlab_monitor/git"
+    autoload :DatabaseDeadTuplesCollector, "gitlab_monitor/database_dead_tuples_collector"
   end
 end

lib/gitlab_monitor/cli.rb

@@ -74,8 +74,63 @@ module GitLab
         end
       end
 
+      class DatabaseDeadTuples
+        COMMAND_NAME = "db-dead-tuples".freeze
+
+        def initialize(args)
+          @options = options(args)
+          @options.parse!
+        end
+
+        def options(args)
+          args.options do |opts|
+            opts.banner = "Usage: #{EXECUTABLE_NAME} #{COMMAND_NAME} [options]"
+            opts.on(
+              "-i", "--interval [NUMBER]", Numeric, "Interval (in seconds) at which data is collected. Default is 60."
+            ) do |val|
+              @interval = val || 60
+            end
+            opts.on("--db-conn=\"dbname=test port=5432\"", "Database connection string") do |val|
+              @db_connection_string = val
+            end
+          end
+        end
+
+        def help
+          @options.help
+        end
+
+        def run
+          validate!
+          run_loop
+        end
+
+        private
+
+        def validate!
+          fail InvalidCLICommand.new(help) unless @db_connection_string
+        end
+
+        def run_loop
+          collector = ::GitLab::Monitor::DatabaseDeadTuplesCollector.new(connection_string: @db_connection_string)
+          metrics   = PrometheusMetrics.new
+
+          loop do
+            result = collector.run
+
+            result.each do |table_name, dead_tuples_count|
+              metrics.add("#{table_name}_dead_tuples", dead_tuples_count)
+            end
+
+            puts metrics.to_s
+
+            sleep @interval
+          end
+        end
+      end
+
       def self.commands
-        [GIT].each_with_object({}) do |command_class, commands|
+        [GIT, DatabaseDeadTuples].each_with_object({}) do |command_class, commands|
           commands[command_class::COMMAND_NAME] = command_class
           commands
         end

lib/gitlab_monitor/database_dead_tuples_collector.rb

+require "pg"
+
+module GitLab
+  module Monitor
+    class DatabaseDeadTuplesCollector
+      attr_reader :result
+
+      def initialize(args)
+        @connection_string = args[:connection_string]
+      end
+
+      def run
+        table_names = connection.exec("SELECT tablename FROM pg_tables WHERE tableowner <> 'postgres'").values.flatten
+        stats       = {}
+
+        table_names.each do |table_name|
+          result = connection.exec("SELECT n_dead_tup FROM pg_stat_user_tables WHERE relname = '#{table_name}'")
+          stats[table_name] = result[0]["n_dead_tup"].to_i
+        end
+
+        stats
+      end
+
+      private
+
+      def connection
+        @connection ||= PG.connect(@connection_string)
+      end
+    end
+  end
+end