Add prometheus text formatter

 + rename controler method to #index from #metrics
 + remove assertion from nullMetric

app/services/metrics_service.rb

@@ -24,11 +24,11 @@ class MetricsService
   private
 
   def formatter
-    @formatter ||= PrometheusText.new
+    @formatter ||= Gitlab::HealthChecks::PrometheusTextFormat.new
   end
 
   def multiprocess_metrics_path
-    @multiprocess_metrics_path ||= Rails.root.join(ENV['prometheus_multiproc_dir'])
+    @multiprocess_metrics_path ||= Rails.root.join(ENV['prometheus_multiproc_dir']).freeze
   end
 
   def metric_to_prom_line(metric)

config/routes.rb

@@ -41,7 +41,7 @@ Rails.application.routes.draw do
   scope path: '-' do
     get 'liveness' => 'health#liveness'
     get 'readiness' => 'health#readiness'
-    get 'metrics' => 'metrics#metrics'
+    resources :metrics, only: [:index]
   end
 
   # Koding route

lib/gitlab/health_checks/prometheus_text.rb → lib/gitlab/health_checks/prometheus_text_format.rb

 module Gitlab::HealthChecks
-  class PrometheusText
+  class PrometheusTextFormat
     def marshal(metrics)
       metrics_with_type_declarations(metrics).join("\n")
     end

lib/gitlab/metrics/null_metric.rb

@@ -5,15 +5,6 @@ module Gitlab
       def method_missing(name, *args, &block)
         nil
       end
-
-      # these methods shouldn't be called when metrics are disabled
-      def get(*args)
-        raise NotImplementedError
-      end
-
-      def values(*args)
-        raise NotImplementedError
-      end
     end
   end
 end

spec/controllers/metrics_controller_spec.rb

@@ -19,14 +19,14 @@ describe MetricsController do
     allow(Gitlab::Metrics).to receive(:prometheus_metrics_enabled?).and_return(true)
   end
 
-  describe '#metrics' do
+  describe '#index' do
     context 'authorization token provided' do
       before do
         request.headers['TOKEN'] = token
       end
 
       it 'returns DB ping metrics' do
-        get :metrics
+        get :index
 
         expect(response.body).to match(/^db_ping_timeout 0$/)
         expect(response.body).to match(/^db_ping_success 1$/)
@@ -34,7 +34,7 @@ describe MetricsController do
       end
 
       it 'returns Redis ping metrics' do
-        get :metrics
+        get :index
 
         expect(response.body).to match(/^redis_ping_timeout 0$/)
         expect(response.body).to match(/^redis_ping_success 1$/)
@@ -42,7 +42,7 @@ describe MetricsController do
       end
 
       it 'returns file system check metrics' do
-        get :metrics
+        get :index
 
         expect(response.body).to match(/^filesystem_access_latency{shard="default"} [0-9\.]+$/)
         expect(response.body).to match(/^filesystem_accessible{shard="default"} 1$/)
@@ -58,7 +58,7 @@ describe MetricsController do
         end
 
         it 'returns proper response' do
-          get :metrics
+          get :index
 
           expect(response.status).to eq(404)
         end
@@ -67,7 +67,7 @@ describe MetricsController do
 
     context 'without authorization token' do
       it 'returns proper response' do
-        get :metrics
+        get :index
 
         expect(response.status).to eq(404)
       end

spec/lib/gitlab/health_checks/prometheus_text_format_spec.rb

+describe Gitlab::HealthChecks::PrometheusTextFormat do
+  let(:metric_class) { Gitlab::HealthChecks::Metric }
+  subject { described_class.new }
+
+  describe '#marshal' do
+    let(:sample_metrics) do
+      [
+        metric_class.new('metric1', 1),
+        metric_class.new('metric2', 2)
+      ]
+    end
+
+    it 'marshal to text with non repeating type definition' do
+      expected = <<-EXPECTED
+# TYPE metric1 gauge
+metric1 1
+# TYPE metric2 gauge
+metric2 2
+EXPECTED
+      expect(subject.marshal(sample_metrics)).to eq(expected.chomp)
+    end
+
+    context 'metrics where name repeats' do
+      let(:sample_metrics) do
+        [
+          metric_class.new('metric1', 1),
+          metric_class.new('metric1', 2),
+          metric_class.new('metric2', 3)
+        ]
+      end
+
+      it 'marshal to text with non repeating type definition' do
+        expected = <<-EXPECTED
+# TYPE metric1 gauge
+metric1 1
+metric1 2
+# TYPE metric2 gauge
+metric2 3
+        EXPECTED
+        expect(subject.marshal(sample_metrics)).to eq(expected.chomp)
+      end
+    end
+  end
+end