Refactor common metrics importer

This refactors common metrics importer for two reasons. 1. To create a
new pattern that can be followed by future importers that will minimize
dependency collision and 2. To allow EE to more easily extend
dependencies.

5 files changed, 140 insertions, 105 deletions

diff --git a/db/importers/common_metrics.rb b/db/importers/common_metrics.rb
new file mode 100644
index 00000000000..411d366ef83
--- /dev/null
+++ b/db/importers/common_metrics.rb
@@ -0,0 +1,17 @@
+require_relative './common_metrics/importer'
+require_relative './common_metrics/prometheus_metric'
+require_relative './common_metrics/prometheus_metric_enums'
+
+require Rails.root.join('ee', 'db', 'importers', 'common_metrics') if Gitlab.ee?
+
+module Importers
+  module CommonMetrics
+  end
+
+  # Patch to preserve old CommonMetricsImporter api
+  module CommonMetricsImporter
+    def self.new(*args)
+      Importers::CommonMetrics::Importer.new(*args)
+    end
+  end
+end
diff --git a/db/importers/common_metrics/importer.rb b/db/importers/common_metrics/importer.rb
new file mode 100644
index 00000000000..24149fbbea6
--- /dev/null
+++ b/db/importers/common_metrics/importer.rb
@@ -0,0 +1,76 @@
+# frozen_string_literal: true
+
+module Importers
+  module CommonMetrics
+    class Importer
+      MissingQueryId = Class.new(StandardError)
+
+      attr_reader :content
+
+      def initialize(filename = 'common_metrics.yml')
+        @content = YAML.load_file(Rails.root.join('config', 'prometheus', filename))
+      end
+
+      def execute
+        PrometheusMetric.reset_column_information
+
+        process_content do |id, attributes|
+          find_or_build_metric!(id)
+            .update!(**attributes)
+        end
+      end
+
+      private
+
+      def process_content(&blk)
+        content['panel_groups'].map do |group|
+          process_group(group, &blk)
+        end
+      end
+
+      def process_group(group, &blk)
+        attributes = {
+          group: find_group_title_key(group['group'])
+        }
+
+        group['panels'].map do |panel|
+          process_panel(panel, attributes, &blk)
+        end
+      end
+
+      def process_panel(panel, attributes, &blk)
+        attributes = attributes.merge(
+          title: panel['title'],
+          y_label: panel['y_label'])
+
+        panel['metrics'].map do |metric_details|
+          process_metric_details(metric_details, attributes, &blk)
+        end
+      end
+
+      def process_metric_details(metric_details, attributes, &blk)
+        attributes = attributes.merge(
+          legend: metric_details['label'],
+          query: metric_details['query_range'],
+          unit: metric_details['unit'])
+
+        yield(metric_details['id'], attributes)
+      end
+
+      def find_or_build_metric!(id)
+        raise MissingQueryId unless id
+
+        PrometheusMetric.common.find_by(identifier: id) ||
+          PrometheusMetric.new(common: true, identifier: id)
+      end
+
+      def find_group_title_key(title)
+        PrometheusMetricEnums.groups[find_group_title(title)]
+      end
+
+      def find_group_title(title)
+        PrometheusMetricEnums.group_titles.invert[title]
+      end
+    end
+  end
+end
diff --git a/db/importers/common_metrics/prometheus_metric.rb b/db/importers/common_metrics/prometheus_metric.rb
new file mode 100644
index 00000000000..9149549c750
--- /dev/null
+++ b/db/importers/common_metrics/prometheus_metric.rb
@@ -0,0 +1,8 @@
+module Importers
+  module CommonMetrics
+    class PrometheusMetric < ActiveRecord::Base
+      enum group: PrometheusMetricEnums.groups
+      scope :common, -> { where(common: true) }
+    end
+  end
+end
diff --git a/db/importers/common_metrics/prometheus_metric_enums.rb b/db/importers/common_metrics/prometheus_metric_enums.rb
new file mode 100644
index 00000000000..50a1081a629
--- /dev/null
+++ b/db/importers/common_metrics/prometheus_metric_enums.rb
@@ -0,0 +1,36 @@
+module Importers
+  module CommonMetrics
+    module PrometheusMetricEnums
+      def self.groups
+        {
+          # built-in groups
+          nginx_ingress_vts: -1,
+          ha_proxy: -2,
+          aws_elb: -3,
+          nginx: -4,
+          kubernetes: -5,
+          nginx_ingress: -6,
+
+          # custom groups
+          business: 0,
+          response: 1,
+          system: 2
+        }
+      end
+
+      def self.group_titles
+        {
+          business: _('Business metrics (Custom)'),
+          response: _('Response metrics (Custom)'),
+          system: _('System metrics (Custom)'),
+          nginx_ingress_vts: _('Response metrics (NGINX Ingress VTS)'),
+          nginx_ingress: _('Response metrics (NGINX Ingress)'),
+          ha_proxy: _('Response metrics (HA Proxy)'),
+          aws_elb: _('Response metrics (AWS ELB)'),
+          nginx: _('Response metrics (NGINX)'),
+          kubernetes: _('System metrics (Kubernetes)')
+        }
+      end
+    end
+  end
+end
diff --git a/db/importers/common_metrics_importer.rb b/db/importers/common_metrics_importer.rb
index 195bde8f34a..cf5f5e181de 100644
--- a/db/importers/common_metrics_importer.rb
+++ b/db/importers/common_metrics_importer.rb
@@ -1,105 +1,3 @@
-# frozen_string_literal: true
-
-module Importers
-  class PrometheusMetric < ActiveRecord::Base
-    enum group: {
-      # built-in groups
-      nginx_ingress_vts: -1,
-      ha_proxy: -2,
-      aws_elb: -3,
-      nginx: -4,
-      kubernetes: -5,
-      nginx_ingress: -6,
-
-      # custom groups
-      business: 0,
-      response: 1,
-      system: 2
-    }
-
-    scope :common, -> { where(common: true) }
-
-    GROUP_TITLES = {
-      business: _('Business metrics (Custom)'),
-      response: _('Response metrics (Custom)'),
-      system: _('System metrics (Custom)'),
-      nginx_ingress_vts: _('Response metrics (NGINX Ingress VTS)'),
-      nginx_ingress: _('Response metrics (NGINX Ingress)'),
-      ha_proxy: _('Response metrics (HA Proxy)'),
-      aws_elb: _('Response metrics (AWS ELB)'),
-      nginx: _('Response metrics (NGINX)'),
-      kubernetes: _('System metrics (Kubernetes)')
-    }.freeze
-  end
-
-  class CommonMetricsImporter
-    MissingQueryId = Class.new(StandardError)
-
-    attr_reader :content
-
-    def initialize(filename = 'common_metrics.yml')
-      @content = YAML.load_file(Rails.root.join('config', 'prometheus', filename))
-    end
-
-    def execute
-      PrometheusMetric.reset_column_information
-
-      process_content do |id, attributes|
-        find_or_build_metric!(id)
-          .update!(**attributes)
-      end
-    end
-
-    private
-
-    def process_content(&blk)
-      content['panel_groups'].map do |group|
-        process_group(group, &blk)
-      end
-    end
-
-    def process_group(group, &blk)
-      attributes = {
-        group: find_group_title_key(group['group'])
-      }
-
-      group['panels'].map do |panel|
-        process_panel(panel, attributes, &blk)
-      end
-    end
-
-    def process_panel(panel, attributes, &blk)
-      attributes = attributes.merge(
-        title: panel['title'],
-        y_label: panel['y_label'])
-
-      panel['metrics'].map do |metric_details|
-        process_metric_details(metric_details, attributes, &blk)
-      end
-    end
-
-    def process_metric_details(metric_details, attributes, &blk)
-      attributes = attributes.merge(
-        legend: metric_details['label'],
-        query: metric_details['query_range'],
-        unit: metric_details['unit'])
-
-      yield(metric_details['id'], attributes)
-    end
-
-    def find_or_build_metric!(id)
-      raise MissingQueryId unless id
-
-      PrometheusMetric.common.find_by(identifier: id) ||
-        PrometheusMetric.new(common: true, identifier: id)
-    end
-
-    def find_group_title_key(title)
-      PrometheusMetric.groups[find_group_title(title)]
-    end
-
-    def find_group_title(title)
-      PrometheusMetric::GROUP_TITLES.invert[title]
-    end
-  end
-end
+# This functionality has been moved to the common_metrics module.
+# This is here only to preserve existing ::Importers::CommonMetricsImporter api
+require_relative './common_metrics'