Add trailing newline to response.

Prometheus requires a trailing newline in its response.

+ cleanup

app/controllers/health_controller.rb

@@ -23,15 +23,27 @@ class HealthController < ActionController::Base
   end
 
   def metrics
-    results = CHECKS.flat_map(&:metrics)
+    response = health_metrics_text + "\n"
+
+    if Gitlab::Metrics.prometheus_metrics_enabled?
+      response += Prometheus::Client::Formats::Text.marshal_multiprocess(ENV['prometheus_multiproc_dir'])
+    end
 
-    response = results.map(&method(:metric_to_prom_line)).join("\n")
-    response = ::Prometheus::Client::Formats::Text.marshal_multiprocess
     render text: response, content_type: 'text/plain; version=0.0.4'
   end
 
   private
 
+  def health_metrics_text
+    results = CHECKS.flat_map(&:metrics)
+
+    types = results.map(&:name)
+              .uniq
+              .map { |metric_name| "# TYPE #{metric_name} gauge" }
+    metrics = results.map(&method(:metric_to_prom_line))
+    types.concat(metrics).join("\n")
+  end
+
   def metric_to_prom_line(metric)
     labels = metric.labels&.map { |key, value| "#{key}=\"#{value}\"" }&.join(',') || ''
     if labels.empty?

app/controllers/sessions_controller.rb

@@ -34,7 +34,6 @@ class SessionsController < Devise::SessionsController
       end
       # hide the signed-in notification
       flash[:notice] = nil
-      PromService.instance.login.increment
       log_audit_event(current_user, with: authentication_method)
       log_user_activity(current_user)
     end
@@ -48,6 +47,10 @@ class SessionsController < Devise::SessionsController
 
   private
 
+  def self.login_counter
+    @login_counter ||= Gitlab::Metrics.counter(:user_session_logins, 'User logins count')
+  end
+
   # Handle an "initial setup" state, where there's only one user, it's an admin,
   # and they require a password change.
   def check_initial_setup
@@ -126,6 +129,7 @@ class SessionsController < Devise::SessionsController
   end
 
   def log_user_activity(user)
+    SessionsController.login_counter.increment
     Users::ActivityService.new(user, 'login').execute
   end
 

app/services/prom_service.rb

-require 'prometheus/client'
-require 'singleton'
-
-class PromService
-  include Singleton
-
-  attr_reader :login
-
-  def initialize
-    @prometheus = Prometheus::Client.registry
-
-    @login = Prometheus::Client::Counter.new(:login, 'Login counter')
-    @prometheus.register(@login)
-  end
-end