Add ApplicationRecord#safe_ensure_unique method

Port of https://dev.gitlab.org/gitlab/gitlab-ee/merge_requests/866
to CE excluding the migration and service changes as they don't
apply to CE.

1 files changed, 14 insertions, 3 deletions

diff --git a/app/models/application_record.rb b/app/models/application_record.rb
index 6976185264e..348468197bf 100644
--- a/app/models/application_record.rb
+++ b/app/models/application_record.rb
@@ -15,6 +15,19 @@ class ApplicationRecord < ActiveRecord::Base
     where(nil).pluck(self.primary_key)
   end
 
+  def self.safe_ensure_unique(retries: 0)
+    transaction(requires_new: true) do
+      yield
+    end
+  rescue ActiveRecord::RecordNotUnique
+    if retries > 0
+      retries -= 1
+      retry
+    end
+
+    false
+  end
+
   def self.safe_find_or_create_by!(*args)
     safe_find_or_create_by(*args).tap do |record|
       record.validate! unless record.persisted?
@@ -22,10 +35,8 @@ class ApplicationRecord < ActiveRecord::Base
   end
 
   def self.safe_find_or_create_by(*args)
-    transaction(requires_new: true) do
+    safe_ensure_unique(retries: 1) do
       find_or_create_by(*args)
     end
-  rescue ActiveRecord::RecordNotUnique
-    retry
   end
 end