Cache the number of user SSH keyscache-user-keys-count

By caching the number of personal SSH keys we reduce the number of
queries necessary on pages such as ProjectsController#show (which can
end up querying this data multiple times).

The cache is refreshed/flushed whenever an SSH key is added, removed, or
when a user is removed.

1 files changed, 34 insertions, 0 deletions

diff --git a/app/services/base_count_service.rb b/app/services/base_count_service.rb
new file mode 100644
index 00000000000..99cc9a196e6
--- /dev/null
+++ b/app/services/base_count_service.rb
@@ -0,0 +1,34 @@
+# Base class for services that count a single resource such as the number of
+# issues for a project.
+class BaseCountService
+  def relation_for_count
+    raise(
+      NotImplementedError,
+      '"relation_for_count" must be implemented and return an ActiveRecord::Relation'
+    )
+  end
+
+  def count
+    Rails.cache.fetch(cache_key, raw: raw?) { uncached_count }.to_i
+  end
+
+  def refresh_cache
+    Rails.cache.write(cache_key, uncached_count, raw: raw?)
+  end
+
+  def uncached_count
+    relation_for_count.count
+  end
+
+  def delete_cache
+    Rails.cache.delete(cache_key)
+  end
+
+  def raw?
+    false
+  end
+
+  def cache_key
+    raise NotImplementedError, 'cache_key must be implemented and return a String'
+  end
+end