Post custom metrics(table count, column count, and comment count) to mackerei.io

mackerel.rake

require 'mackerel/client'

namespace :mackerel do
  namespace :service_metric do
    namespace :database do
      desc 'Post table count, column count, and comment count to mackerel.'
      task post: :environment do
        client = Mackerel::Client.new(mackerel_api_key: ENV['MACKEREL_API_KEY'])
        service_name = ENV['MACKEREL_SERVICE_NAME']
        time = Time.zone.now.to_i
        system_view_names = %w(
          pg_stat_statements
          geography_columns
          geometry_columns
          raster_columns
          raster_overviews
        )
        tables = ApplicationRecord.connection.tables
        views = ApplicationRecord.connection.views - system_view_names
        columns = (tables + views).map { |table| ApplicationRecord.connection.columns(table) }.flatten
        comments = columns.reject { |column| column.comment.nil? }
        metrics = [
          {
            name: 'database.tables',
            time: time,
            value: tables.count + views.count,
          },
          {
            name: 'database.columns',
            time: time,
            value: columns.count,
          },
          {
            name: 'database.comments',
            time: time,
            value: comments.count,
          },
        ]
        # 通信ができない場合やMackerel API Keyがない場合に例外が起きても無視する
        begin
          client.post_service_metrics(service_name, metrics)
        rescue
          nil
        end
      end
    end
  end
end

# マイグレーションタスクを実行されたら、Mackerelに送る。実装はannotateを参考にした。
# see https://github.com/ctran/annotate_models/blob/516ed58e5662e32fca5114c6dbe20be93a4e5507/lib/tasks/annotate_models_migrate.rake
migration_tasks = %w(db:migrate db:migrate:up db:migrate:down db:migrate:reset db:migrate:redo db:rollback)
if defined?(Rails::Application) && Rails.version.split('.').first.to_i >= 6
  require 'active_record'

  databases = ActiveRecord::Tasks::DatabaseTasks.setup_initial_database_yaml

  ActiveRecord::Tasks::DatabaseTasks.for_each(databases) do |spec_name|
    migration_tasks.concat(%w(db:migrate db:migrate:up db:migrate:down).map { |task| "#{task}:#{spec_name}" })
  end
end

migration_tasks.each do |task|
  next unless Rake::Task.task_defined?(task)

  Rake::Task[task].enhance do
    Rake::Task[Rake.application.top_level_tasks.last].enhance do
      Rake::Task['mackerel:service_metric:database:post'].invoke if Rails.env.development?
    end
  end
end