diff --git a/.rubocop.yml b/.rubocop.yml
index 6852589b..727ed6a6 100644
--- a/.rubocop.yml
+++ b/.rubocop.yml
@@ -20,3 +20,9 @@ Style/Documentation:
   Enabled: false
 Layout/SpaceInsideHashLiteralBraces:
   EnforcedStyle: no_space
+RSpec/MultipleExpectations:
+  Max: 2
+Metrics/BlockLength:
+  Exclude:
+    - 'spec/**/*.rb'
+    - 'config/environments/*.rb'
diff --git a/Gemfile b/Gemfile
index 33d7e809..5c046280 100644
--- a/Gemfile
+++ b/Gemfile
@@ -21,6 +21,7 @@ gem 'nokogiri'
 gem 'pagedown-bootstrap-rails'
 gem 'pg'
 gem 'proforma', git: 'https://github.com/openHPI/proforma.git', tag: 'v0.5'
+gem 'prometheus_exporter'
 gem 'pry-byebug'
 gem 'puma'
 gem 'pundit'
diff --git a/Gemfile.lock b/Gemfile.lock
index 36ebb8cd..1da41ed4 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -248,6 +248,8 @@ GEM
       ast (~> 2.4.1)
     path_expander (1.1.0)
     pg (1.2.3)
+    prometheus_exporter (0.7.0)
+      webrick
     pry (0.13.1)
       coderay (~> 1.1)
       method_source (~> 1.0)
@@ -469,6 +471,7 @@ GEM
       rack-proxy (>= 0.6.1)
       railties (>= 5.2)
       semantic_range (>= 2.3.0)
+    webrick (1.7.0)
     websocket (1.2.9)
     websocket-driver (0.7.3)
       websocket-extensions (>= 0.1.0)
@@ -515,6 +518,7 @@ DEPENDENCIES
   pagedown-bootstrap-rails
   pg
   proforma!
+  prometheus_exporter
   pry-byebug
   pry-rails
   puma
diff --git a/README.md b/README.md
index 3e64dd31..3dda93c2 100644
--- a/README.md
+++ b/README.md
@@ -9,7 +9,7 @@ CodeOcean
 
 ## Introduction
 
-CodeOcean is an educational, web-based execution and development environment for practical programming exercises designed for the use in Massive Open Online Courses (MOOCs). 
+CodeOcean is an educational, web-based execution and development environment for practical programming exercises designed for the use in Massive Open Online Courses (MOOCs).
 
 The programming courses offered on openHPI include practical programming exercises that are provided on a web-based code execution platform called CodeOcean. The platform has many advantages for learners and teachers alike:
 
@@ -22,7 +22,7 @@ CodeOcean is mainly used in the context of MOOCs (such as those offered on openH
 
 ## Development Setup
 
-Please refer to the [Local Setup Guide](docs/LOCAL_SETUP.md) for more details. 
+Please refer to the [Local Setup Guide](docs/LOCAL_SETUP.md) for more details.
 
 ### Mandatory Steps
 
@@ -50,3 +50,9 @@ In order to execute code submissions using Docker, source code files are written
 
 - create production configuration files (*database.production.yml*, …)
 - customize *config/deploy/production.rb* if you want to deploy using [Capistrano](http://capistranorb.com/)
+
+## Monitoring
+- We use a [Prometheus Exporter](https://github.com/discourse/prometheus_exporter) and a [Telegraf Client](https://github.com/jgraichen/telegraf-ruby)
+- The Telegraf client collects the data from the Prometheus endpoint, adds its own datasets and forwards them to an InfluxDB
+- The Prometheus Exporter must be started separately **before** running the Rails server via `bundle exec prometheus_exporter`
+- The InfluxDB data can be visualized using Grafana, for example. There is also an adapted [dashboard](docs/grafana/prometheus_exporter_grafana_dashboard.json) for this purpose
\ No newline at end of file
diff --git a/Vagrantfile b/Vagrantfile
index 074ded8c..795f1cf9 100644
--- a/Vagrantfile
+++ b/Vagrantfile
@@ -1,14 +1,19 @@
+# frozen_string_literal: true
+
 # -*- mode: ruby -*-
 # vi: set ft=ruby :
 
 Vagrant.configure(2) do |config|
-  config.vm.box = "ubuntu/focal64"
-  config.vm.provider "virtualbox" do |v|
+  config.vm.box = 'ubuntu/focal64'
+  config.vm.provider 'virtualbox' do |v|
     v.memory = 4096
     v.cpus = 4
   end
-  config.vm.network "forwarded_port", host_ip: "127.0.0.1", host: 3000, guest: 3000
-  config.vm.synced_folder ".", "/home/vagrant/codeocean"
-  config.vm.synced_folder "../dockercontainerpool", "/home/vagrant/dockercontainerpool"
-  config.vm.provision "shell", path: "provision/provision.vagrant.sh", privileged: false
+  config.vm.network 'forwarded_port',
+                    host_ip: ENV['LISTEN_ADDRESS'] || '127.0.0.1',
+                    host: 3000,
+                    guest: 3000
+  config.vm.synced_folder '.', '/home/vagrant/codeocean'
+  config.vm.synced_folder '../dockercontainerpool', '/home/vagrant/dockercontainerpool'
+  config.vm.provision 'shell', path: 'provision/provision.vagrant.sh', privileged: false
 end
diff --git a/app/models/application_record.rb b/app/models/application_record.rb
index 10a4cba8..71fbba5b 100644
--- a/app/models/application_record.rb
+++ b/app/models/application_record.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class ApplicationRecord < ActiveRecord::Base
   self.abstract_class = true
 end
diff --git a/app/models/comment.rb b/app/models/comment.rb
index f1d3a559..7c4e7014 100644
--- a/app/models/comment.rb
+++ b/app/models/comment.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 class Comment < ApplicationRecord
   # inherit the creation module: encapsulates that this is a polymorphic user, offers some aliases and makes sure that all necessary attributes are set.
   include Creation
@@ -8,4 +10,12 @@ class Comment < ApplicationRecord
   belongs_to :file, class_name: 'CodeOcean::File'
   belongs_to :user, polymorphic: true
   # after_save :trigger_rfc_action_cable_from_comment
+
+  def request_for_comment
+    RequestForComment.find_by(submission_id: file.context.id)
+  end
+
+  def only_comment_for_rfc?
+    request_for_comment.comments.one?
+  end
 end
diff --git a/app/models/request_for_comment.rb b/app/models/request_for_comment.rb
index d96b0a76..6dfb1ae4 100644
--- a/app/models/request_for_comment.rb
+++ b/app/models/request_for_comment.rb
@@ -1,29 +1,27 @@
+# frozen_string_literal: true
+
 class RequestForComment < ApplicationRecord
   include Creation
   include ActionCableHelper
 
+  # SOLVED:      The author explicitly marked the RfC as solved.
+  # SOFT_SOLVED: The author did not mark the RfC as solved but reached the maximum score in the corresponding exercise at any time.
+  # ONGOING:     The author did not mark the RfC as solved and did not reach the maximum score in the corresponding exercise yet.
+  STATE = [SOLVED = :solved, SOFT_SOLVED = :soft_solved, ONGOING = :unsolved].freeze
+
   belongs_to :submission
   belongs_to :exercise
   belongs_to :file, class_name: 'CodeOcean::File'
 
   has_many :comments, through: :submission
-  has_many :subscriptions
+  has_many :subscriptions, dependent: :destroy
 
   scope :unsolved, -> { where(solved: [false, nil]) }
-  scope :in_range, -> (from, to) { where(created_at: from..to) }
+  scope :in_range, ->(from, to) { where(created_at: from..to) }
+  scope :with_comments, -> { select { |rfc| rfc.comments.any? } }
 
   # after_save :trigger_rfc_action_cable
 
-    def self.last_per_user(n = 5)
-      from("(#{row_number_user_sql}) as request_for_comments")
-          .where("row_number <= ?", n)
-          .group('request_for_comments.id, request_for_comments.user_id, request_for_comments.user_type,
-                  request_for_comments.exercise_id, request_for_comments.file_id, request_for_comments.question,
-                request_for_comments.created_at, request_for_comments.updated_at, request_for_comments.solved,
-                request_for_comments.full_score_reached, request_for_comments.submission_id, request_for_comments.row_number')
-        # ugly, but necessary
-  end
-
   # not used right now, finds the last submission for the respective user and exercise.
   # might be helpful to check whether the exercise has been solved in the meantime.
   def last_submission
@@ -46,27 +44,64 @@ class RequestForComment < ApplicationRecord
   end
 
   def comments_count
-    submission.files.map { |file| file.comments.size}.sum
+    submission.files.map { |file| file.comments.size }.sum
   end
 
   def commenters
     comments.map(&:user).uniq
   end
 
-  def self.with_last_activity
-    self.joins('join "submissions" s on s.id = request_for_comments.submission_id
+  def comments?
+    comments.any?
+  end
+
+  def to_s
+    "RFC-#{id}"
+  end
+
+  def current_state
+    state(solved, full_score_reached)
+  end
+
+  def old_state
+    state(solved_before_last_save, full_score_reached_before_last_save)
+  end
+
+  private
+
+  def state(solved, full_score_reached)
+    if solved
+      SOLVED
+    elsif full_score_reached
+      SOFT_SOLVED
+    else
+      ONGOING
+    end
+  end
+
+  class << self
+    def with_last_activity
+      joins('join "submissions" s on s.id = request_for_comments.submission_id
                 left outer join "files" f on f.context_id = s.id
                 left outer join "comments" c on c.file_id = f.id')
         .group('request_for_comments.id')
         .select('request_for_comments.*, max(c.updated_at) as last_comment')
-  end
+    end
 
-  def to_s
-    "RFC-" + self.id.to_s
-  end
+    def last_per_user(count = 5)
+      from("(#{row_number_user_sql}) as request_for_comments")
+        .where('row_number <= ?', count)
+        .group('request_for_comments.id, request_for_comments.user_id, request_for_comments.user_type,
+                  request_for_comments.exercise_id, request_for_comments.file_id, request_for_comments.question,
+                request_for_comments.created_at, request_for_comments.updated_at, request_for_comments.solved,
+                request_for_comments.full_score_reached, request_for_comments.submission_id, request_for_comments.row_number')
+      # ugly, but necessary
+    end
 
     private
-    def self.row_number_user_sql
-      select("id, user_id, user_type, exercise_id, file_id, question, created_at, updated_at, solved, full_score_reached, submission_id, row_number() OVER (PARTITION BY user_id, user_type ORDER BY created_at DESC) as row_number").to_sql
+
+    def row_number_user_sql
+      select('id, user_id, user_type, exercise_id, file_id, question, created_at, updated_at, solved, full_score_reached, submission_id, row_number() OVER (PARTITION BY user_id, user_type ORDER BY created_at DESC) as row_number').to_sql
     end
+  end
 end
diff --git a/config/code_ocean.yml.ci b/config/code_ocean.yml.ci
index acb6f808..5b15067e 100644
--- a/config/code_ocean.yml.ci
+++ b/config/code_ocean.yml.ci
@@ -7,3 +7,5 @@ test:
     enabled: false
   codeocean_events:
     enabled: false
+  prometheus_exporter:
+    enabled: false
diff --git a/config/code_ocean.yml.example b/config/code_ocean.yml.example
index 78c705a5..72f7ed84 100644
--- a/config/code_ocean.yml.example
+++ b/config/code_ocean.yml.example
@@ -19,9 +19,15 @@ development:
   codeharbor:
     enabled: true
     url: https://codeharbor.openhpi.de
+  prometheus_exporter:
+    enabled: false
 
 production:
   <<: *default
+  prometheus_exporter:
+    enabled: true
 
 test:
   <<: *default
+  prometheus_exporter:
+    enabled: false
diff --git a/config/environments/development.rb b/config/environments/development.rb
index b91a19b5..4ed50f91 100644
--- a/config/environments/development.rb
+++ b/config/environments/development.rb
@@ -1,24 +1,26 @@
+# frozen_string_literal: true
+
 Rails.application.configure do
   # Verifies that versions and hashed value of the package contents in the project's package.json
   config.webpacker.check_yarn_integrity = true
   # Settings specified here will take precedence over those in config/application.rb.
 
-  config.web_console.whitelisted_ips = '192.168.0.0/16'  
-  
+  config.web_console.whitelisted_ips = '192.168.0.0/16'
+
   # In the development environment your application's code is reloaded on
   # every request. This slows down response time but is perfect for development
   # since you don't have to restart the web server when you make code changes.
   config.cache_classes = false
 
-  # Do not eager load code on boot.
-  config.eager_load = false
+  # Eager load code for prometheus exporter
+  config.eager_load = true
 
   # Show full error reports.
   config.consider_all_requests_local = true
 
   # Enable/disable caching. By default caching is disabled.
   # Run rails dev:cache to toggle caching.
-  if Rails.root.join('tmp', 'caching-dev.txt').exist?
+  if Rails.root.join('tmp/caching-dev.txt').exist?
     config.action_controller.perform_caching = true
 
     config.cache_store = :memory_store
diff --git a/config/environments/production.rb b/config/environments/production.rb
index 86b0fac5..fd72163c 100644
--- a/config/environments/production.rb
+++ b/config/environments/production.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 Rails.application.configure do
   # Verifies that versions and hashed value of the package contents in the project's package.json
   config.webpacker.check_yarn_integrity = false
@@ -10,6 +12,7 @@ Rails.application.configure do
   # your application in memory, allowing both threaded web servers
   # and those relying on copy on write to perform better.
   # Rake tasks automatically ignore this option for performance.
+  # Eager load is also required for the prometheus exporter
   config.eager_load = true
 
   # Full error reports are disabled and caching is turned on.
@@ -90,8 +93,8 @@ Rails.application.configure do
   # require 'syslog/logger'
   # config.logger = ActiveSupport::TaggedLogging.new(Syslog::Logger.new 'app-name')
 
-  if ENV["RAILS_LOG_TO_STDOUT"].present?
-    logger           = ActiveSupport::Logger.new(STDOUT)
+  if ENV['RAILS_LOG_TO_STDOUT'].present?
+    logger           = ActiveSupport::Logger.new($stdout)
     logger.formatter = config.log_formatter
     config.logger    = ActiveSupport::TaggedLogging.new(logger)
   end
diff --git a/config/environments/staging.rb b/config/environments/staging.rb
index f9b09b3c..41a7e30a 100644
--- a/config/environments/staging.rb
+++ b/config/environments/staging.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 Rails.application.configure do
   # Settings specified here will take precedence over those in config/application.rb.
 
@@ -11,9 +13,10 @@ Rails.application.configure do
   #       your application in memory, allowing both threaded web servers
   #       and those relying on copy on write to perform better.
   #       Rake tasks automatically ignore this option for performance.
-  config.eager_load = false
+  # Eager load code for prometheus exporter
+  config.eager_load = true
 
-  #enable web console in staging
+  # enable web console in staging
   config.web_console.development_only = false
 
   # Show full error reports and disable caching.
diff --git a/config/environments/test.rb b/config/environments/test.rb
index 5d112d40..c23bcbf2 100644
--- a/config/environments/test.rb
+++ b/config/environments/test.rb
@@ -1,3 +1,5 @@
+# frozen_string_literal: true
+
 Rails.application.configure do
   # Settings specified here will take precedence over those in config/application.rb.
 
@@ -10,7 +12,8 @@ Rails.application.configure do
   # Do not eager load code on boot. This avoids loading your whole application
   # just for the purpose of running a single test. If you are using a tool that
   # preloads Rails for running tests, you may have to set it to true.
-  config.eager_load = false
+  # Eager load code for prometheus exporter
+  config.eager_load = true
 
   # Configure public file server for tests with Cache-Control for performance.
   config.public_file_server.enabled = true
@@ -47,7 +50,7 @@ Rails.application.configure do
   # Raises error for missing translations
   # config.action_view.raise_on_missing_translations = true
 
-  #config.logger = Logger.new(STDOUT)
+  # config.logger = Logger.new($stdout)
   # Set log level
-  #config.log_level = :DEBUG
+  # config.log_level = :DEBUG
 end
diff --git a/config/initializers/prometheus.rb b/config/initializers/prometheus.rb
new file mode 100644
index 00000000..c9c3aa7b
--- /dev/null
+++ b/config/initializers/prometheus.rb
@@ -0,0 +1,10 @@
+# frozen_string_literal: true
+
+return unless CodeOcean::Config.new(:code_ocean).read[:prometheus_exporter][:enabled]
+return if Rake.application.top_level_tasks.to_s.include?('db:')
+
+# Add metric callbacks to all models
+ApplicationRecord.include Prometheus::Record
+
+# Initialize the counters according to the db
+Prometheus::Controller.initialize_metrics
diff --git a/db/seeds/hello_world/exercise_spec.rb b/db/seeds/hello_world/exercise_spec.rb
index d5419b13..e7e53ab4 100644
--- a/db/seeds/hello_world/exercise_spec.rb
+++ b/db/seeds/hello_world/exercise_spec.rb
@@ -1,6 +1,6 @@
 describe 'Exercise' do
   it "outputs 'Hello World" do
-    expect(STDOUT).to receive(:puts).with('Hello World')
+    expect($stdout).to receive(:puts).with('Hello World')
     require './exercise'
   end
 end
diff --git a/docs/LOCAL_SETUP.md b/docs/LOCAL_SETUP.md
index e8cda783..627c81c5 100644
--- a/docs/LOCAL_SETUP.md
+++ b/docs/LOCAL_SETUP.md
@@ -47,6 +47,14 @@ The default credentials for the administrator are:
 - email: `admin@example.org`
 - password: `admin`
 
+For exporting metrics, start the prometeus exporter by running
+
+```bash
+bundle exec prometheus_exporter
+```
+
+in the CodeOcean folder before starting CodeOcean.
+
 ## Execution Environments
 
 Every exercise is executed in an execution environment which is based on a docker image. In order to install a new image, have a look at the container of the openHPI team on [DockerHub](https://hub.docker.com/u/openhpi). For example you can add an [image for ruby](https://hub.docker.com/layers/openhpi/co_execenv_ruby/latest/images/sha256-70f597320567678bf8d0146d93fb1bd98457abe61c3b642e832d4e4fbe7f4526) by executing `docker pull openhpi/co_execenv_ruby:latest`.  
diff --git a/docs/grafana/prometheus_exporter_grafana_dashboard.json b/docs/grafana/prometheus_exporter_grafana_dashboard.json
new file mode 100644
index 00000000..f2266277
--- /dev/null
+++ b/docs/grafana/prometheus_exporter_grafana_dashboard.json
@@ -0,0 +1,1693 @@
+{
+  "annotations": {
+    "list": [
+      {
+        "builtIn": 1,
+        "datasource": "-- Grafana --",
+        "enable": true,
+        "hide": true,
+        "iconColor": "rgba(0, 211, 255, 1)",
+        "name": "Annotations & Alerts",
+        "type": "dashboard"
+      }
+    ]
+  },
+  "editable": true,
+  "gnetId": null,
+  "graphTooltip": 0,
+  "id": 6,
+  "iteration": 1612278241744,
+  "links": [],
+  "panels": [
+    {
+      "aliasColors": {},
+      "bars": false,
+      "dashLength": 10,
+      "dashes": false,
+      "datasource": null,
+      "fieldConfig": {
+        "defaults": {
+          "custom": {
+            "align": null,
+            "filterable": false
+          },
+          "mappings": [],
+          "thresholds": {
+            "mode": "absolute",
+            "steps": [
+              {
+                "color": "green",
+                "value": null
+              },
+              {
+                "color": "red",
+                "value": 80
+              }
+            ]
+          }
+        },
+        "overrides": []
+      },
+      "fill": 1,
+      "fillGradient": 0,
+      "gridPos": {
+        "h": 8,
+        "w": 12,
+        "x": 0,
+        "y": 0
+      },
+      "hiddenSeries": false,
+      "id": 2,
+      "legend": {
+        "avg": false,
+        "current": false,
+        "max": false,
+        "min": false,
+        "show": false,
+        "total": false,
+        "values": false
+      },
+      "lines": true,
+      "linewidth": 1,
+      "nullPointMode": "null",
+      "options": {
+        "alertThreshold": true
+      },
+      "percentage": false,
+      "pluginVersion": "7.3.6",
+      "pointradius": 2,
+      "points": false,
+      "renderer": "flot",
+      "seriesOverrides": [],
+      "spaceLength": 10,
+      "stack": false,
+      "steppedLine": false,
+      "targets": [
+        {
+          "groupBy": [
+            {
+              "params": [
+                "$__interval"
+              ],
+              "type": "time"
+            },
+            {
+              "params": [
+                "null"
+              ],
+              "type": "fill"
+            }
+          ],
+          "orderByTime": "ASC",
+          "policy": "default",
+          "query": "from(bucket: \"${bucket}\")\n  |> range(start: v.timeRangeStart, stop:v.timeRangeStop)\n  |> filter(fn: (r) =>\n    r._measurement == \"prometheus\" and\n    r._field == \"instance_count\" and\n    r.class == \"Submission\"\n  )\n  |> aggregateWindow(every: v.windowPeriod, fn: last)\n  |> map(fn: (r) => ({_value:r._value, _time:r._time, _field:r.class}))",
+          "refId": "A",
+          "resultFormat": "time_series",
+          "select": [
+            [
+              {
+                "params": [
+                  "value"
+                ],
+                "type": "field"
+              },
+              {
+                "params": [],
+                "type": "mean"
+              }
+            ]
+          ],
+          "tags": []
+        }
+      ],
+      "thresholds": [],
+      "timeFrom": null,
+      "timeRegions": [],
+      "timeShift": null,
+      "title": "Amount of Submissions",
+      "tooltip": {
+        "shared": true,
+        "sort": 0,
+        "value_type": "individual"
+      },
+      "type": "graph",
+      "xaxis": {
+        "buckets": null,
+        "mode": "time",
+        "name": null,
+        "show": true,
+        "values": []
+      },
+      "yaxes": [
+        {
+          "$$hashKey": "object:73",
+          "format": "short",
+          "label": null,
+          "logBase": 1,
+          "max": null,
+          "min": null,
+          "show": true
+        },
+        {
+          "$$hashKey": "object:74",
+          "format": "short",
+          "label": null,
+          "logBase": 1,
+          "max": null,
+          "min": null,
+          "show": true
+        }
+      ],
+      "yaxis": {
+        "align": false,
+        "alignLevel": null
+      }
+    },
+    {
+      "collapsed": false,
+      "datasource": null,
+      "gridPos": {
+        "h": 1,
+        "w": 24,
+        "x": 0,
+        "y": 8
+      },
+      "id": 12,
+      "panels": [],
+      "title": "Users",
+      "type": "row"
+    },
+    {
+      "datasource": null,
+      "fieldConfig": {
+        "defaults": {
+          "custom": {},
+          "mappings": [],
+          "thresholds": {
+            "mode": "absolute",
+            "steps": [
+              {
+                "color": "green",
+                "value": null
+              },
+              {
+                "color": "red",
+                "value": 80
+              }
+            ]
+          }
+        },
+        "overrides": []
+      },
+      "gridPos": {
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+          "orderByTime": "ASC",
+          "policy": "default",
+          "query": "from(bucket: \"codemoon\")\n  |> range(start: v.timeRangeStart, stop:v.timeRangeStop)\n  |> filter(fn: (r) =>\n    r._measurement == \"prometheus\" and\n    r._field == \"instance_count\" and\n    r.class == \"Testrun\"\n  )\n  |> aggregateWindow(every: 1m, fn: last)\n  |> difference(columns: [\"_value\"], nonNegative: true)\n  |> map(fn: (r) => ({_value:r._value, _time:r._time, _field:\"Container Requests\"}))\n",
+          "refId": "A",
+          "resultFormat": "time_series",
+          "select": [
+            [
+              {
+                "params": [
+                  "value"
+                ],
+                "type": "field"
+              },
+              {
+                "params": [],
+                "type": "mean"
+              }
+            ]
+          ],
+          "tags": []
+        }
+      ],
+      "thresholds": [],
+      "timeFrom": null,
+      "timeRegions": [],
+      "timeShift": null,
+      "title": "Container Requests per minute",
+      "tooltip": {
+        "shared": true,
+        "sort": 0,
+        "value_type": "individual"
+      },
+      "type": "graph",
+      "xaxis": {
+        "buckets": null,
+        "mode": "time",
+        "name": null,
+        "show": true,
+        "values": []
+      },
+      "yaxes": [
+        {
+          "$$hashKey": "object:1017",
+          "format": "short",
+          "label": null,
+          "logBase": 1,
+          "max": null,
+          "min": null,
+          "show": true
+        },
+        {
+          "$$hashKey": "object:1018",
+          "format": "short",
+          "label": null,
+          "logBase": 1,
+          "max": null,
+          "min": null,
+          "show": true
+        }
+      ],
+      "yaxis": {
+        "align": false,
+        "alignLevel": null
+      }
+    },
+    {
+      "collapsed": false,
+      "datasource": null,
+      "gridPos": {
+        "h": 1,
+        "w": 24,
+        "x": 0,
+        "y": 26
+      },
+      "id": 14,
+      "panels": [],
+      "title": "Request For Comments",
+      "type": "row"
+    },
+    {
+      "datasource": null,
+      "fieldConfig": {
+        "defaults": {
+          "custom": {},
+          "mappings": [],
+          "thresholds": {
+            "mode": "absolute",
+            "steps": [
+              {
+                "color": "green",
+                "value": null
+              },
+              {
+                "color": "red",
+                "value": 80
+              }
+            ]
+          }
+        },
+        "overrides": []
+      },
+      "gridPos": {
+        "h": 3,
+        "w": 5,
+        "x": 0,
+        "y": 27
+      },
+      "id": 26,
+      "options": {
+        "colorMode": "value",
+        "graphMode": "none",
+        "justifyMode": "auto",
+        "orientation": "auto",
+        "reduceOptions": {
+          "calcs": [
+            "last"
+          ],
+          "fields": "",
+          "values": false
+        },
+        "textMode": "auto"
+      },
+      "pluginVersion": "7.3.6",
+      "targets": [
+        {
+          "groupBy": [
+            {
+              "params": [
+                "$__interval"
+              ],
+              "type": "time"
+            },
+            {
+              "params": [
+                "null"
+              ],
+              "type": "fill"
+            }
+          ],
+          "orderByTime": "ASC",
+          "policy": "default",
+          "query": "from(bucket: \"${bucket}\")\n  |> range(start: v.timeRangeStart, stop:v.timeRangeStop)\n  |> filter(fn: (r) =>\n    r._measurement == \"prometheus\" and\n    r._field == \"instance_count\" and\n    r.class == \"Comment\"\n  )\n  |> last()\n",
+          "refId": "A",
+          "resultFormat": "time_series",
+          "select": [
+            [
+              {
+                "params": [
+                  "value"
+                ],
+                "type": "field"
+              },
+              {
+                "params": [],
+                "type": "mean"
+              }
+            ]
+          ],
+          "tags": []
+        }
+      ],
+      "timeFrom": null,
+      "timeShift": null,
+      "title": "Comments",
+      "transformations": [
+        {
+          "id": "organize",
+          "options": {
+            "excludeByName": {},
+            "indexByName": {},
+            "renameByName": {
+              "instance_count {class=\"ExternalUser\", environment=\"production\", fqdn=\"codeocean.internal-codemoon.xopic.de\", host=\"codeocean\", platform=\"codeocean\", site=\"codeocean\", url=\"unix:///var/www/app/shared/tmp/sockets/puma.sock\"}": "ExternalUser",
+              "instance_count {class=\"InternalUser\", environment=\"production\", fqdn=\"codeocean.internal-codemoon.xopic.de\", host=\"codeocean\", platform=\"codeocean\", site=\"codeocean\", url=\"unix:///var/www/app/shared/tmp/sockets/puma.sock\"}": "InternalUser"
+            }
+          }
+        }
+      ],
+      "type": "stat"
+    },
+    {
+      "aliasColors": {},
+      "breakPoint": "50%",
+      "cacheTimeout": null,
+      "combine": {
+        "label": "Others",
+        "threshold": 0
+      },
+      "datasource": null,
+      "fieldConfig": {
+        "defaults": {
+          "custom": {}
+        },
+        "overrides": []
+      },
+      "fontSize": "100%",
+      "format": "short",
+      "gridPos": {
+        "h": 9,
+        "w": 10,
+        "x": 5,
+        "y": 27
+      },
+      "id": 29,
+      "interval": null,
+      "legend": {
+        "percentage": true,
+        "show": true,
+        "values": true
+      },
+      "legendType": "Right side",
+      "links": [],
+      "nullPointMode": "connected",
+      "pieType": "pie",
+      "pluginVersion": "7.3.6",
+      "strokeWidth": 1,
+      "targets": [
+        {
+          "groupBy": [
+            {
+              "params": [
+                "$__interval"
+              ],
+              "type": "time"
+            },
+            {
+              "params": [
+                "null"
+              ],
+              "type": "fill"
+            }
+          ],
+          "orderByTime": "ASC",
+          "policy": "default",
+          "query": "from(bucket: \"codemoon\")\n  |> range(start: v.timeRangeStart, stop: v.timeRangeStop)\n  |> filter(fn: (r) => r[\"_measurement\"] == \"prometheus\")\n  |> filter(fn: (r) => r[\"_field\"] == \"rfc_count\")\n  |> aggregateWindow(every: v.windowPeriod, fn: last)\n  |> map(fn: (r) => ({_value:r._value, _time:r._time, _field:r.state}))",
+          "refId": "A",
+          "resultFormat": "time_series",
+          "select": [
+            [
+              {
+                "params": [
+                  "value"
+                ],
+                "type": "field"
+              },
+              {
+                "params": [],
+                "type": "mean"
+              }
+            ]
+          ],
+          "tags": []
+        }
+      ],
+      "timeFrom": null,
+      "timeShift": null,
+      "title": "Request For Comments Ratio",
+      "type": "grafana-piechart-panel",
+      "valueName": "current"
+    },
+    {
+      "aliasColors": {},
+      "bars": false,
+      "dashLength": 10,
+      "dashes": false,
+      "datasource": null,
+      "fieldConfig": {
+        "defaults": {
+          "custom": {}
+        },
+        "overrides": []
+      },
+      "fill": 1,
+      "fillGradient": 0,
+      "gridPos": {
+        "h": 9,
+        "w": 9,
+        "x": 15,
+        "y": 27
+      },
+      "hiddenSeries": false,
+      "id": 32,
+      "legend": {
+        "avg": false,
+        "current": false,
+        "max": false,
+        "min": false,
+        "show": true,
+        "total": false,
+        "values": false
+      },
+      "lines": true,
+      "linewidth": 1,
+      "nullPointMode": "null",
+      "options": {
+        "alertThreshold": true
+      },
+      "percentage": false,
+      "pluginVersion": "7.3.6",
+      "pointradius": 2,
+      "points": false,
+      "renderer": "flot",
+      "seriesOverrides": [
+        {
+          "$$hashKey": "object:529"
+        },
+        {
+          "alias": "unsolved",
+          "yaxis": 1
+        }
+      ],
+      "spaceLength": 10,
+      "stack": true,
+      "steppedLine": false,
+      "targets": [
+        {
+          "groupBy": [
+            {
+              "params": [
+                "$__interval"
+              ],
+              "type": "time"
+            },
+            {
+              "params": [
+                "null"
+              ],
+              "type": "fill"
+            }
+          ],
+          "orderByTime": "ASC",
+          "policy": "default",
+          "query": "from(bucket: \"codemoon\")\n  |> range(start: v.timeRangeStart, stop:v.timeRangeStop)\n  |> filter(fn: (r) =>\n    r._measurement == \"prometheus\" and\n    r._field == \"rfc_count\"\n  )\n  |> aggregateWindow(every: v.windowPeriod, fn: last)\n  |> map(fn: (r) => ({_value:r._value, _time:r._time, _field:r.state}))\n",
+          "refId": "A",
+          "resultFormat": "time_series",
+          "select": [
+            [
+              {
+                "params": [
+                  "value"
+                ],
+                "type": "field"
+              },
+              {
+                "params": [],
+                "type": "mean"
+              }
+            ]
+          ],
+          "tags": []
+        }
+      ],
+      "thresholds": [],
+      "timeFrom": null,
+      "timeRegions": [],
+      "timeShift": null,
+      "title": "RFC count ",
+      "tooltip": {
+        "shared": true,
+        "sort": 2,
+        "value_type": "individual"
+      },
+      "type": "graph",
+      "xaxis": {
+        "buckets": null,
+        "mode": "time",
+        "name": null,
+        "show": true,
+        "values": []
+      },
+      "yaxes": [
+        {
+          "$$hashKey": "object:663",
+          "format": "short",
+          "label": null,
+          "logBase": 1,
+          "max": null,
+          "min": null,
+          "show": true
+        },
+        {
+          "$$hashKey": "object:664",
+          "format": "short",
+          "label": null,
+          "logBase": 1,
+          "max": null,
+          "min": null,
+          "show": true
+        }
+      ],
+      "yaxis": {
+        "align": false,
+        "alignLevel": null
+      }
+    },
+    {
+      "datasource": null,
+      "fieldConfig": {
+        "defaults": {
+          "custom": {},
+          "mappings": [],
+          "thresholds": {
+            "mode": "absolute",
+            "steps": [
+              {
+                "color": "green",
+                "value": null
+              },
+              {
+                "color": "red",
+                "value": 80
+              }
+            ]
+          }
+        },
+        "overrides": []
+      },
+      "gridPos": {
+        "h": 3,
+        "w": 5,
+        "x": 0,
+        "y": 30
+      },
+      "id": 27,
+      "options": {
+        "colorMode": "value",
+        "graphMode": "none",
+        "justifyMode": "auto",
+        "orientation": "auto",
+        "reduceOptions": {
+          "calcs": [
+            "last"
+          ],
+          "fields": "",
+          "values": false
+        },
+        "textMode": "auto"
+      },
+      "pluginVersion": "7.3.6",
+      "targets": [
+        {
+          "groupBy": [
+            {
+              "params": [
+                "$__interval"
+              ],
+              "type": "time"
+            },
+            {
+              "params": [
+                "null"
+              ],
+              "type": "fill"
+            }
+          ],
+          "orderByTime": "ASC",
+          "policy": "default",
+          "query": "from(bucket: \"${bucket}\")\n  |> range(start: v.timeRangeStart, stop:v.timeRangeStop)\n  |> filter(fn: (r) =>\n    r._measurement == \"prometheus\" and\n    r._field == \"instance_count\" and\n    r.class == \"RequestForComment\"\n  )\n  |> last()\n",
+          "refId": "A",
+          "resultFormat": "time_series",
+          "select": [
+            [
+              {
+                "params": [
+                  "value"
+                ],
+                "type": "field"
+              },
+              {
+                "params": [],
+                "type": "mean"
+              }
+            ]
+          ],
+          "tags": []
+        }
+      ],
+      "timeFrom": null,
+      "timeShift": null,
+      "title": "Request For Comments",
+      "transformations": [
+        {
+          "id": "organize",
+          "options": {
+            "excludeByName": {},
+            "indexByName": {},
+            "renameByName": {
+              "instance_count {class=\"ExternalUser\", environment=\"production\", fqdn=\"codeocean.internal-codemoon.xopic.de\", host=\"codeocean\", platform=\"codeocean\", site=\"codeocean\", url=\"unix:///var/www/app/shared/tmp/sockets/puma.sock\"}": "ExternalUser",
+              "instance_count {class=\"InternalUser\", environment=\"production\", fqdn=\"codeocean.internal-codemoon.xopic.de\", host=\"codeocean\", platform=\"codeocean\", site=\"codeocean\", url=\"unix:///var/www/app/shared/tmp/sockets/puma.sock\"}": "InternalUser"
+            }
+          }
+        }
+      ],
+      "type": "stat"
+    },
+    {
+      "datasource": null,
+      "fieldConfig": {
+        "defaults": {
+          "custom": {},
+          "mappings": [],
+          "thresholds": {
+            "mode": "absolute",
+            "steps": [
+              {
+                "color": "green",
+                "value": null
+              },
+              {
+                "color": "red",
+                "value": 80
+              }
+            ]
+          }
+        },
+        "overrides": []
+      },
+      "gridPos": {
+        "h": 3,
+        "w": 5,
+        "x": 0,
+        "y": 33
+      },
+      "id": 30,
+      "options": {
+        "colorMode": "value",
+        "graphMode": "none",
+        "justifyMode": "auto",
+        "orientation": "auto",
+        "reduceOptions": {
+          "calcs": [
+            "last"
+          ],
+          "fields": "",
+          "values": false
+        },
+        "textMode": "auto"
+      },
+      "pluginVersion": "7.3.6",
+      "targets": [
+        {
+          "groupBy": [
+            {
+              "params": [
+                "$__interval"
+              ],
+              "type": "time"
+            },
+            {
+              "params": [
+                "null"
+              ],
+              "type": "fill"
+            }
+          ],
+          "orderByTime": "ASC",
+          "policy": "default",
+          "query": "from(bucket: \"${bucket}\")\n  |> range(start: v.timeRangeStart, stop:v.timeRangeStop)\n  |> filter(fn: (r) =>\n    r._measurement == \"prometheus\" and\n    r._field == \"rfc_commented_count\"\n  )\n  |> last()\n",
+          "refId": "A",
+          "resultFormat": "time_series",
+          "select": [
+            [
+              {
+                "params": [
+                  "value"
+                ],
+                "type": "field"
+              },
+              {
+                "params": [],
+                "type": "mean"
+              }
+            ]
+          ],
+          "tags": []
+        }
+      ],
+      "timeFrom": null,
+      "timeShift": null,
+      "title": "RFCs with Comments",
+      "transformations": [
+        {
+          "id": "organize",
+          "options": {
+            "excludeByName": {},
+            "indexByName": {},
+            "renameByName": {
+              "instance_count {class=\"ExternalUser\", environment=\"production\", fqdn=\"codeocean.internal-codemoon.xopic.de\", host=\"codeocean\", platform=\"codeocean\", site=\"codeocean\", url=\"unix:///var/www/app/shared/tmp/sockets/puma.sock\"}": "ExternalUser",
+              "instance_count {class=\"InternalUser\", environment=\"production\", fqdn=\"codeocean.internal-codemoon.xopic.de\", host=\"codeocean\", platform=\"codeocean\", site=\"codeocean\", url=\"unix:///var/www/app/shared/tmp/sockets/puma.sock\"}": "InternalUser"
+            }
+          }
+        }
+      ],
+      "type": "stat"
+    }
+  ],
+  "refresh": false,
+  "schemaVersion": 26,
+  "style": "dark",
+  "tags": [],
+  "templating": {
+    "list": [
+      {
+        "current": {
+          "selected": false,
+          "text": "codemoon",
+          "value": "codemoon"
+        },
+        "error": null,
+        "hide": 2,
+        "label": null,
+        "name": "bucket",
+        "options": [
+          {
+            "selected": true,
+            "text": "codemoon",
+            "value": "codemoon"
+          }
+        ],
+        "query": "codemoon",
+        "skipUrlSync": false,
+        "type": "constant"
+      }
+    ]
+  },
+  "time": {
+    "from": "now-6h",
+    "to": "now"
+  },
+  "timepicker": {},
+  "timezone": "",
+  "title": "CodeOcean Exporter",
+  "uid": "H3jZcSLGk",
+  "version": 32
+}
\ No newline at end of file
diff --git a/lib/prometheus.rb b/lib/prometheus.rb
new file mode 100644
index 00000000..eaad2831
--- /dev/null
+++ b/lib/prometheus.rb
@@ -0,0 +1,3 @@
+# frozen_string_literal: true
+
+module Prometheus; end
diff --git a/lib/prometheus/controller.rb b/lib/prometheus/controller.rb
new file mode 100644
index 00000000..d2d85767
--- /dev/null
+++ b/lib/prometheus/controller.rb
@@ -0,0 +1,100 @@
+# frozen_string_literal: true
+
+require 'prometheus_exporter/client'
+
+module Prometheus
+  module Controller
+    # TODO: currently active users - as Event
+    # TODO: active_in_last_hour
+    # TODO: autosaves_per_minute
+
+    class << self
+      def initialize_metrics
+        register_metrics
+        initialize_instance_count
+        initialize_rfc_metrics
+      end
+
+      def register_metrics
+        prometheus = PrometheusExporter::Client.default
+
+        @instance_count = prometheus.register(:gauge, :instance_count, help: 'Instance count')
+        # counts solved, soft_solved, ongoing
+        @rfc_count = prometheus.register(:gauge, :rfc_count, help: 'Count of RfCs in each state')
+        # counts commented
+        @rfc_commented_count = prometheus.register(:gauge, :rfc_commented_count, help: 'Count of commented RfCs')
+      end
+
+      def initialize_instance_count
+        ApplicationRecord.descendants.reject(&:abstract_class).each do |each|
+          @instance_count.observe(each.count, class: each.name)
+        end
+      end
+
+      def initialize_rfc_metrics
+        # Initialize rfc metric
+        @rfc_count.observe(RequestForComment.unsolved.where(full_score_reached: false).count,
+                           state: RequestForComment::ONGOING)
+        @rfc_count.observe(RequestForComment.unsolved.where(full_score_reached: true).count,
+                           state: RequestForComment::SOFT_SOLVED)
+        @rfc_count.observe(RequestForComment.where(solved: true).count,
+                           state: RequestForComment::SOLVED)
+
+        # count of rfcs with comments
+        @rfc_commented_count.observe(RequestForComment.with_comments.count)
+      end
+
+      def update_notification(object)
+        Rails.logger.debug("Prometheus metric updated for #{object.class.name}")
+
+        case object
+        when RequestForComment
+          update_rfc(object)
+        end
+      end
+
+      def create_notification(object)
+        @instance_count.increment(class: object.class.name)
+        Rails.logger.debug("Prometheus instance count increased for #{object.class.name}")
+
+        case object
+        when RequestForComment
+          create_rfc(object)
+        when Comment
+          create_comment(object)
+        end
+      end
+
+      def destroy_notification(object)
+        @instance_count.decrement(class: object.class.name)
+        Rails.logger.debug("Prometheus instance count decreased for #{object.class.name}")
+
+        case object
+        when Comment
+          destroy_comment(object)
+        end
+      end
+
+      def create_rfc(rfc)
+        @rfc_count.increment(state: rfc.current_state)
+      end
+
+      def update_rfc(rfc)
+        @rfc_count.decrement(state: rfc.old_state)
+        # If the metrics are scraped when the execution is exactly at the place of this comment,
+        # the old state is already decremented while the new state is not yet incremented and
+        # the metric is therefore inconsistent. As this is only a temporarily off by one error
+        # in the metric and a solution (e.g. a mutex) would be complex, this is acceptable.
+        @rfc_count.increment(state: rfc.current_state)
+      end
+
+      def create_comment(comment)
+        @rfc_commented_count.increment if comment.only_comment_for_rfc?
+      end
+
+      def destroy_comment(comment)
+        @rfc_commented_count.decrement unless comment.request_for_comment.comments?
+      end
+    end
+  end
+end
diff --git a/lib/prometheus/record.rb b/lib/prometheus/record.rb
new file mode 100644
index 00000000..ad7631e4
--- /dev/null
+++ b/lib/prometheus/record.rb
@@ -0,0 +1,27 @@
+# frozen_string_literal: true
+
+module Prometheus
+  module Record
+    extend ActiveSupport::Concern
+
+    included do
+      after_create_commit :create_notification
+      after_destroy_commit :destroy_notification
+      after_update_commit :update_notification
+    end
+
+    private
+
+    def create_notification
+      Prometheus::Controller.create_notification self
+    end
+
+    def destroy_notification
+      Prometheus::Controller.destroy_notification self
+    end
+
+    def update_notification
+      Prometheus::Controller.update_notification self
+    end
+  end
+end
diff --git a/spec/factories/request_for_comment.rb b/spec/factories/request_for_comment.rb
index 30d40330..169632a5 100644
--- a/spec/factories/request_for_comment.rb
+++ b/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
diff --git a/spec/features/prometheus/controller_spec.rb b/spec/features/prometheus/controller_spec.rb
new file mode 100644
index 00000000..a3ab68a6
--- /dev/null
+++ b/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
diff --git a/spec/models/request_for_comment_spec.rb b/spec/models/request_for_comment_spec.rb
new file mode 100644
index 00000000..f4038841
--- /dev/null
+++ b/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
diff --git a/spec/rails_helper.rb b/spec/rails_helper.rb
index 8de4fc82..e450dad2 100644
--- a/spec/rails_helper.rb
+++ b/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.
diff --git a/spec/support/prometheus_client_stub.rb b/spec/support/prometheus_client_stub.rb
new file mode 100644
index 00000000..4aa2ad8a
--- /dev/null
+++ b/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