1 files changed, 18 insertions, 0 deletions
diff --git a/app/models/discussion.rb b/app/models/discussion.rb
index 70aa02063cc..076d8cc280c 100644
--- a/app/models/discussion.rb
+++ b/app/models/discussion.rb
@@ -7,6 +7,9 @@ class Discussion
   include GlobalID::Identification
   include ResolvableDiscussion
 
+  # Bump this if we need to refresh the cached versions of discussions
+  CACHE_VERSION = 1
+
   attr_reader :notes, :context_noteable
 
   delegate  :created_at,
@@ -158,4 +161,19 @@ class Discussion
   def reply_attributes
     first_note.slice(:type, :noteable_type, :noteable_id, :commit_id, :discussion_id)
   end
+
+  def cache_key
+    # Need this so cache will be invalidated when note within a discussion
+    # has been deleted.
+    notes_sha = Digest::SHA1.hexdigest(notes.map(&:id).join(':'))
+
+    [
+      CACHE_VERSION,
+      notes.last.latest_cached_markdown_version,
+      id,
+      notes_sha,
+      notes.max_by(&:updated_at).updated_at,
+      resolved_at
+    ].join(':')
+  end
 end