Fix memory leak in readiness health check endpoint

app/controllers/health_controller.rb

@@ -19,8 +19,19 @@ def api_key_tester
     render json: { ok: is_good_result }, status: response_status
   end
 
+  def self.impatient_mongoid_client
+    @impatient_mongoid_client ||= Mongo::Client.new(
+      Errbit::Config.mongo_url,
+      server_selection_timeout: 0.5,
+      connect_timeout:          0.5,
+      socket_timeout:           0.5
+    )
+  end
+
 private
 
+  delegate :impatient_mongoid_client, to: :class
+
   def run_mongo_check
     # collections might be empty which is ok but it will raise an exception if
     # database cannot be contacted
@@ -31,13 +42,4 @@ def run_mongo_check
   ensure
     impatient_mongoid_client.close
   end
-
-  def impatient_mongoid_client
-    @impatient_mongoid_client ||= Mongo::Client.new(
-      Errbit::Config.mongo_url,
-      server_selection_timeout: 0.5,
-      connect_timeout:          0.5,
-      socket_timeout:           0.5
-    )
-  end
 end

spec/requests/health_controller_spec.rb

@@ -2,6 +2,12 @@
   let(:errbit_app) { Fabricate(:app, api_key: 'APIKEY') }
 
   describe "readiness" do
+    before do
+      if HealthController.instance_variable_defined? :@impatient_mongoid_client
+        HealthController.remove_instance_variable :@impatient_mongoid_client
+      end
+    end
+
     it 'can let you know when the app is ready to receive requests' do
       get '/health/readiness'
       expect(response).to be_success