#46 Add Prometheus exporter

spec/factories/request_for_comment.rb

@@ -1,5 +1,7 @@
+# frozen_string_literal: true
+
 FactoryBot.define do
-  factory :rfc, class: RequestForComment do
+  factory :rfc, class: 'RequestForComment' do
     association :user, factory: :external_user
     association :submission
     association :exercise, factory: :dummy
@@ -7,5 +9,12 @@ FactoryBot.define do
     sequence :question do |n|
       "test question #{n}"
     end
+
+    factory :rfc_with_comment, class: 'RequestForComment' do
+      after(:create) do |rfc|
+        rfc.file = rfc.submission.files.first
+        Comment.create(file: rfc.file, user: rfc.user, text: "comment for rfc #{rfc.question}")
+      end
+    end
   end
 end

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

spec/models/request_for_comment_spec.rb

@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+describe RequestForComment do
+  let!(:rfc) { FactoryBot.create(:rfc) }
+
+  describe 'scope with_comments' do
+    let!(:rfc2) { FactoryBot.create(:rfc_with_comment) }
+
+    it 'includes all RfCs with comments' do
+      expect(described_class.with_comments).to include(rfc2)
+    end
+
+    it 'does not include any RfC without a comment' do
+      expect(described_class.with_comments).not_to include(rfc)
+    end
+  end
+end

spec/rails_helper.rb

@@ -1,7 +1,10 @@
+# frozen_string_literal: true
+
 # This file is copied to spec/ when you run 'rails generate rspec:install'
 ENV['RAILS_ENV'] ||= 'test'
 require 'spec_helper'
-require File.expand_path('../../config/environment', __FILE__)
+require 'support/prometheus_client_stub'
+require File.expand_path('../config/environment', __dir__)
 require 'rspec/rails'
 require 'pundit/rspec'
 
@@ -12,7 +15,7 @@ require 'pundit/rspec'
 # run twice. It is recommended that you do not name files matching this glob to
 # end with _spec.rb. You can configure this pattern with with the --pattern
 # option on the command line or in ~/.rspec, .rspec or `.rspec-local`.
-Dir[Rails.root.join('spec/support/**/*.rb')].each { |f| require f }
+Dir[Rails.root.join('spec/support/**/*.rb')].sort.each { |f| require f }
 
 # Checks for pending migrations before tests are run.
 # If you are not using ActiveRecord, you can remove this line.

spec/support/prometheus_client_stub.rb

@@ -0,0 +1,15 @@
+# frozen_string_literal: true
+
+require 'prometheus_exporter/client'
+require 'rails_helper'
+
+module Prometheus
+  # A stub to disable server functionality in the specs and stub all registered metrics
+  module StubClient
+    def send(str)
+      # Do nothing
+    end
+  end
+
+  PrometheusExporter::Client.prepend StubClient
+end