#46 Add Prometheus exporter

spec/features/prometheus/controller_spec.rb

@@ -0,0 +1,101 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+describe Prometheus::Controller do
+  def stub_metrics
+    %i[increment decrement observe].each do |method|
+      %i[@instance_count @rfc_count @rfc_commented_count].each do |metric|
+        allow(described_class.instance_variable_get(metric)).to receive(method)
+      end
+    end
+  end
+
+  before do
+    ApplicationRecord.include Prometheus::Record
+    described_class.initialize_metrics
+    stub_metrics
+  end
+
+  describe 'instance count' do
+    it 'initializes the metrics with the current database entries' do
+      FactoryBot.create_list(:proxy_exercise, 3)
+      described_class.register_metrics
+      stub_metrics
+      described_class.initialize_instance_count
+      expect(described_class.instance_variable_get(:@instance_count)).to(have_received(:observe).with(ProxyExercise.count, class: ProxyExercise.name).once)
+    end
+
+    it 'gets notified when an object is created' do
+      allow(described_class).to receive(:create_notification)
+      proxy_exercise = FactoryBot.create(:proxy_exercise)
+      expect(described_class).to have_received(:create_notification).with(proxy_exercise).once
+    end
+
+    it 'gets notified when an object is destroyed' do
+      allow(described_class).to receive(:destroy_notification)
+      proxy_exercise = FactoryBot.create(:proxy_exercise).destroy
+      expect(described_class).to have_received(:destroy_notification).with(proxy_exercise).once
+    end
+
+    it 'increments gauge when creating a new instance' do
+      FactoryBot.create(:proxy_exercise)
+      expect(described_class.instance_variable_get(:@instance_count)).to(
+        have_received(:increment).with(class: ProxyExercise.name).once
+      )
+    end
+
+    it 'decrements gauge when deleting an object' do
+      FactoryBot.create(:proxy_exercise).destroy
+      expect(described_class.instance_variable_get(:@instance_count)).to(
+        have_received(:decrement).with(class: ProxyExercise.name).once
+      )
+    end
+  end
+
+  describe 'rfc count' do
+    context 'when initializing an rfc' do
+      it 'updates rfc count when creating an ongoing rfc' do
+        FactoryBot.create(:rfc)
+        expect(described_class.instance_variable_get(:@rfc_count)).to(
+          have_received(:increment).with(state: RequestForComment::ONGOING).once
+        )
+      end
+    end
+
+    context 'when changing the state of an rfc' do
+      let(:rfc) { FactoryBot.create(:rfc) }
+
+      it 'updates rfc count when soft-solving an rfc' do
+        rfc.full_score_reached = true
+        rfc.save
+        expect(described_class.instance_variable_get(:@rfc_count)).to(have_received(:increment).with(state: RequestForComment::SOFT_SOLVED).once)
+        expect(described_class.instance_variable_get(:@rfc_count)).to(have_received(:decrement).with(state: RequestForComment::ONGOING).once)
+      end
+
+      it 'updates rfc count when solving an rfc' do
+        rfc.solved = true
+        rfc.save
+        expect(described_class.instance_variable_get(:@rfc_count)).to(have_received(:increment).with(state: RequestForComment::SOLVED).once)
+        expect(described_class.instance_variable_get(:@rfc_count)).to(have_received(:decrement).with(state: RequestForComment::ONGOING).once)
+      end
+    end
+
+    context 'when commenting an rfc' do
+      it 'updates comment metric when commenting an rfc' do
+        FactoryBot.create(:rfc_with_comment)
+        expect(described_class.instance_variable_get(:@rfc_commented_count)).to have_received(:increment)
+      end
+
+      it 'does not update comment metric when commenting an rfc that already has a comment' do
+        rfc = FactoryBot.create(:rfc_with_comment)
+        expect(described_class.instance_variable_get(:@rfc_commented_count)).to have_received(:increment).once
+
+        Comment.create(file: rfc.file, user: rfc.user, text: "comment a for rfc #{rfc.question}")
+        Comment.create(file: rfc.file, user: rfc.user, text: "comment b for rfc #{rfc.question}")
+        # instance count has only been updated for the creation of the commented rfc and not for additional comments
+        expect(described_class.instance_variable_get(:@rfc_commented_count)).to have_received(:increment).once
+      end
+    end
+  end
+end