Cache Appearance instances in Redis

This caches the result of Appearance.first in a similar fashion to how
ApplicationSetting instances are cached. We also add some NOT NULL
constraints to the table and correct the timestamp types.

Fixes gitlab-org/gitlab-ce#36066, fixes gitlab-org/gitlab-ce#31698

1 files changed, 20 insertions, 0 deletions

diff --git a/app/models/appearance.rb b/app/models/appearance.rb
index f9c48482be7..ff15689ecac 100644
--- a/app/models/appearance.rb
+++ b/app/models/appearance.rb
@@ -8,7 +8,27 @@ class Appearance < ActiveRecord::Base
   validates :logo,        file_size: { maximum: 1.megabyte }
   validates :header_logo, file_size: { maximum: 1.megabyte }
 
+  validate :single_appearance_row, on: :create
+
   mount_uploader :logo,         AttachmentUploader
   mount_uploader :header_logo,  AttachmentUploader
   has_many :uploads, as: :model, dependent: :destroy # rubocop:disable Cop/ActiveRecordDependent
+
+  CACHE_KEY = 'current_appearance'.freeze
+
+  after_commit :flush_redis_cache
+
+  def self.current
+    Rails.cache.fetch(CACHE_KEY) { first }
+  end
+
+  def flush_redis_cache
+    Rails.cache.delete(CACHE_KEY)
+  end
+
+  def single_appearance_row
+    if self.class.any?
+      errors.add(:single_appearance_row, 'Only 1 appearances row can exist')
+    end
+  end
 end