Refactor DeploymentMetric to reuse code

Re-use shared Prometheus::Adapter code. Move that code out of
app/services to lib/gitlab as it's generic PORO code, not a service.

app/controllers/projects/prometheus/metrics_controller.rb

@@ -23,7 +23,7 @@ module Projects
       private
 
       def prometheus_adapter
-        @prometheus_adapter ||= ::Prometheus::AdapterService.new(project, project.deployment_platform&.cluster).prometheus_adapter
+        @prometheus_adapter ||= ::Gitlab::Prometheus::Adapter.new(project, project.deployment_platform&.cluster).prometheus_adapter
       end
 
       def require_prometheus_metrics!

app/models/deployment_metrics.rb

@@ -34,20 +34,10 @@ class DeploymentMetrics
 
   def prometheus_adapter
     strong_memoize(:prometheus_adapter) do
-      service = project.find_or_initialize_service('prometheus')
-
-      if service.can_query?
-        service
-      else
-        cluster_prometheus
-      end
+      Gitlab::Prometheus::Adapter.new(project, cluster).prometheus_adapter
     end
   end
 
-  def cluster_prometheus
-    cluster.application_prometheus if cluster&.application_prometheus_available?
-  end
-
   def has_metrics_and_can_query?
     has_metrics? && prometheus_adapter.can_query?
   end

app/models/environment.rb

@@ -225,11 +225,9 @@ class Environment < ApplicationRecord
     prometheus_adapter.query(:additional_metrics_environment, self, *args.map(&:to_f))
   end
 
-  # rubocop: disable CodeReuse/ServiceClass
   def prometheus_adapter
-    @prometheus_adapter ||= Prometheus::AdapterService.new(project, deployment_platform&.cluster).prometheus_adapter
+    @prometheus_adapter ||= Gitlab::Prometheus::Adapter.new(project, deployment_platform&.cluster).prometheus_adapter
   end
-  # rubocop: enable CodeReuse/ServiceClass
 
   def slug
     super.presence || generate_slug

app/services/prometheus/adapter_service.rb

-# frozen_string_literal: true
-
-module Prometheus
-  class AdapterService
-    attr_reader :project, :cluster
-
-    def initialize(project, cluster)
-      @project = project
-      @cluster = cluster
-    end
-
-    def prometheus_adapter
-      @prometheus_adapter ||= if service_prometheus_adapter.can_query?
-                                service_prometheus_adapter
-                              else
-                                cluster_prometheus_adapter
-                              end
-    end
-
-    def service_prometheus_adapter
-      project.find_or_initialize_service('prometheus')
-    end
-
-    def cluster_prometheus_adapter
-      application = cluster&.application_prometheus
-
-      application if application&.available?
-    end
-  end
-end

ee/app/models/ee/environment.rb

@@ -81,7 +81,7 @@ module EE
     end
 
     def cluster_prometheus_adapter
-      @cluster_prometheus_adapter ||= Prometheus::AdapterService.new(project, deployment_platform&.cluster).cluster_prometheus_adapter
+      @cluster_prometheus_adapter ||= ::Gitlab::Prometheus::Adapter.new(project, deployment_platform&.cluster).cluster_prometheus_adapter
     end
 
     def protected?

lib/gitlab/prometheus/adapter.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module Prometheus
+    class Adapter
+      attr_reader :project, :cluster
+
+      def initialize(project, cluster)
+        @project = project
+        @cluster = cluster
+      end
+
+      def prometheus_adapter
+        @prometheus_adapter ||= if service_prometheus_adapter.can_query?
+                                  service_prometheus_adapter
+                                else
+                                  cluster_prometheus_adapter
+                                end
+      end
+
+      def cluster_prometheus_adapter
+        application = cluster&.application_prometheus
+
+        application if application&.available?
+      end
+
+      private
+
+      def service_prometheus_adapter
+        project.find_or_initialize_service('prometheus')
+      end
+    end
+  end
+end

spec/controllers/projects/prometheus/metrics_controller_spec.rb

@@ -85,7 +85,7 @@ describe Projects::Prometheus::MetricsController do
     end
 
     it 'calls prometheus adapter service' do
-      expect_next_instance_of(::Prometheus::AdapterService) do |instance|
+      expect_next_instance_of(::Gitlab::Prometheus::Adapter) do |instance|
         expect(instance).to receive(:prometheus_adapter)
       end
 

spec/finders/projects/serverless/functions_finder_spec.rb

@@ -108,7 +108,7 @@ describe Projects::Serverless::FunctionsFinder do
       let(:finder) { described_class.new(project) }
 
       before do
-        allow(Prometheus::AdapterService).to receive(:new).and_return(double(prometheus_adapter: prometheus_adapter))
+        allow(Gitlab::Prometheus::Adapter).to receive(:new).and_return(double(prometheus_adapter: prometheus_adapter))
         allow(prometheus_adapter).to receive(:query).and_return(prometheus_empty_body('matrix'))
       end
 

spec/services/prometheus/adapter_service_spec.rb → spec/lib/gitlab/prometheus/adapter_spec.rb

@@ -2,7 +2,7 @@
 
 require 'spec_helper'
 
-describe Prometheus::AdapterService do
+describe Gitlab::Prometheus::Adapter do
   let_it_be(:project) { create(:project) }
   let_it_be(:cluster, reload: true) { create(:cluster, :provided_by_user, environment_scope: '*', projects: [project]) }
 

spec/models/environment_spec.rb

@@ -1112,7 +1112,7 @@ describe Environment, :use_clean_rails_memory_store_caching do
 
   describe '#prometheus_adapter' do
     it 'calls prometheus adapter service' do
-      expect_next_instance_of(Prometheus::AdapterService) do |instance|
+      expect_next_instance_of(Gitlab::Prometheus::Adapter) do |instance|
         expect(instance).to receive(:prometheus_adapter)
       end