Rescue RuntimeError when "too many loops" occur

With this workaround we temporarily prevent an
exception from Fugit gem to be raised in
Gitlab::Ci::CronParser

lib/gitlab/ci/cron_parser.rb

@@ -13,7 +13,7 @@ module Gitlab
 
       def next_time_from(time)
         @cron_line ||= try_parse_cron(@cron, @cron_timezone)
-        @cron_line.next_time(time).utc.in_time_zone(Time.zone) if @cron_line.present?
+        find_next_time(time) if @cron_line.present?
       end
 
       def cron_valid?
@@ -49,6 +49,14 @@ module Gitlab
       def try_parse_cron(cron, cron_timezone)
         Fugit::Cron.parse("#{cron} #{cron_timezone}")
       end
+
+      def find_next_time(time)
+        @cron_line.next_time(time).utc.in_time_zone(Time.zone)
+      rescue RuntimeError => error
+        raise error unless error.message =~ /too many loops/
+        # Fugit::Cron raises a RuntimeError if :next_time does not find the next schedule 
+        # given an invalid pattern - E.g. try_parse_cron('0 12 31 2 *')
+      end
     end
   end
 end

spec/lib/gitlab/ci/cron_parser_spec.rb

@@ -181,6 +181,13 @@ describe Gitlab::Ci::CronParser do
 
       it { expect(subject).to be_nil }
     end
+
+    context 'when cron is scheduled to a non existent day' do
+      let(:cron) { '0 12 31 2 *' }
+      let(:cron_timezone) { 'UTC' }
+
+      it { expect(subject).to be_nil }
+    end
   end
 
   describe '#cron_valid?' do