From 52f4e834f293c9fdbf5805639d022ac4e3856b75 Mon Sep 17 00:00:00 2001
From: Eugen Rochko <eugen@zeonfederated.com>
Date: Thu, 26 May 2022 22:14:47 +0200
Subject: [PATCH] Fix concurrent unfollowing decrementing follower count more
 than once (#18527)

---
 app/services/unfollow_service.rb | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/app/services/unfollow_service.rb b/app/services/unfollow_service.rb
index 151f3674fd..d83a60e4e7 100644
--- a/app/services/unfollow_service.rb
+++ b/app/services/unfollow_service.rb
@@ -2,6 +2,8 @@
 
 class UnfollowService < BaseService
   include Payloadable
+  include Redisable
+  include Lockable
 
   # Unfollow and notify the remote user
   # @param [Account] source_account Where to unfollow from
@@ -13,7 +15,9 @@ class UnfollowService < BaseService
     @target_account = target_account
     @options        = options
 
-    unfollow! || undo_follow_request!
+    with_lock("relationship:#{[source_account.id, target_account.id].sort.join(':')}") do
+      unfollow! || undo_follow_request!
+    end
   end
 
   private