Memoize CI config node validator to prevent leaks

lib/gitlab/ci/config/node/validatable.rb

@@ -7,13 +7,11 @@ module Gitlab
 
           class_methods do
             def validator
-              validator = Class.new(Node::Validator)
-
+              @validator ||= Class.new(Node::Validator).tap do |validator|
                 if defined?(@validations)
                   @validations.each { |rules| validator.class_eval(&rules) }
                 end
-
-              validator
+              end
             end
 
             private

spec/lib/gitlab/ci/config/node/validatable_spec.rb

@@ -23,6 +23,10 @@ describe Gitlab::Ci::Config::Node::Validatable do
         .to be Gitlab::Ci::Config::Node::Validator
     end
 
+    it 'returns only one validator to mitigate leaks' do
+      expect { node.validator }.not_to change { node.validator }
+    end
+
     context 'when validating node instance' do
       let(:node_instance) { node.new }