Merge branch 'new_metric_umlu' into 'master'

Introduce new New Service Ping metric - UMAU

See merge request gitlab-org/gitlab!88631

config/metrics/counts_28d/20220525231314_unique_monthly_active_users.yml

+---
+key_path: counts_monthly.unique_active_users
+name:
+description: Users that have a last_activity_on date within the past 28 days
+product_category:
+product_section: dev
+product_stage: manage
+product_group: group::manage
+value_type: number
+status: active
+milestone: "15.1"
+introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/88631
+time_frame: 28d
+data_source: database
+data_category: optional
+instrumentation_class: UniqueActiveUsersMetric
+distribution:
+- ce
+- ee
+tier:
+- free
+- premium
+- ultimate

lib/gitlab/usage/metrics/instrumentations/unique_active_users_metric.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module Usage
+    module Metrics
+      module Instrumentations
+        class UniqueActiveUsersMetric < DatabaseMetric
+          operation :count
+          relation { ::User.active }
+
+          metric_options do
+            {
+              batch_size: 10_000
+            }
+          end
+
+          def time_constraints
+            case time_frame
+            when '28d'
+              monthly_time_range_db_params(column: :last_activity_on)
+            else
+              super
+            end
+          end
+        end
+      end
+    end
+  end
+end

spec/lib/gitlab/usage/metrics/instrumentations/unique_active_users_metric_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Gitlab::Usage::Metrics::Instrumentations::UniqueActiveUsersMetric do
+  let_it_be(:user1) { create(:user, last_activity_on: 1.day.ago) }
+  let_it_be(:user2) { create(:user, last_activity_on: 5.days.ago) }
+  let_it_be(:user3) { create(:user, last_activity_on: 50.days.ago) }
+  let_it_be(:user4) { create(:user) }
+  let_it_be(:user5) { create(:user, user_type: 1, last_activity_on: 5.days.ago ) } # support bot
+  let_it_be(:user6) { create(:user, state: 'blocked') }
+
+  context '28d' do
+    let(:start) { 30.days.ago.to_date.to_s }
+    let(:finish) { 2.days.ago.to_date.to_s }
+    let(:expected_value) { 1 }
+    let(:expected_query) do
+      "SELECT COUNT(\"users\".\"id\") FROM \"users\" WHERE (\"users\".\"state\" IN ('active')) AND " \
+      "(\"users\".\"user_type\" IS NULL OR \"users\".\"user_type\" IN (6, 4)) AND \"users\".\"last_activity_on\" " \
+      "BETWEEN '#{start}' AND '#{finish}'"
+    end
+
+    it_behaves_like 'a correct instrumented metric value and query', { time_frame: '28d' }
+  end
+
+  context 'all' do
+    let(:expected_value) { 4 }
+
+    it_behaves_like 'a correct instrumented metric value', { time_frame: 'all' }
+  end
+end