Introduce a new CacheableAttributes concern

Signed-off-by: Rémy Coutable <remy@rymai.me>

1 files changed, 54 insertions, 0 deletions

diff --git a/app/models/concerns/cacheable_attributes.rb b/app/models/concerns/cacheable_attributes.rb
new file mode 100644
index 00000000000..b32459fdabf
--- /dev/null
+++ b/app/models/concerns/cacheable_attributes.rb
@@ -0,0 +1,54 @@
+module CacheableAttributes
+  extend ActiveSupport::Concern
+
+  included do
+    after_commit { self.class.expire }
+  end
+
+  class_methods do
+    # Can be overriden
+    def current_without_cache
+      last
+    end
+
+    def cache_key
+      "#{name}:#{Gitlab::VERSION}:#{Gitlab.migrations_hash}:json".freeze
+    end
+
+    def defaults
+      {}
+    end
+
+    def build_from_defaults(attributes = {})
+      new(defaults.merge(attributes))
+    end
+
+    def cached
+      json_attributes = Rails.cache.read(cache_key)
+      return nil unless json_attributes.present?
+
+      build_from_defaults(JSON.parse(json_attributes))
+    end
+
+    def current
+      cached_record = cached
+      return cached_record if cached_record.present?
+
+      current_without_cache.tap { |current_record| current_record&.cache! }
+    rescue
+      # Fall back to an uncached value if there are any problems (e.g. Redis down)
+      current_without_cache
+    end
+
+    def expire
+      Rails.cache.delete(cache_key)
+    rescue
+      # Gracefully handle when Redis is not available. For example,
+      # omnibus may fail here during gitlab:assets:compile.
+    end
+  end
+
+  def cache!
+    Rails.cache.write(self.class.cache_key, attributes.to_json)
+  end
+end