Improve multiple branch push performance by memoizing permission checking

If you attempt to push thousands of branches at once, the 60-second timeout
will occur because GitAccess checking does a lot of work to check if the
user has permission to push to a branch. This changes does two things:

1. Instead of making 1 DB query per branch push, use a memoized list of protected branches to check
2. Memoize what permissions the user has to perform on this project

On a test of 10,000 branch pushes, this prevents gitlab-shell from hitting the 60-second
timeout.

Closes #17225

1 files changed, 6 insertions, 1 deletions

diff --git a/lib/gitlab/git_access.rb b/lib/gitlab/git_access.rb
index 6cb41239871..d2a0e316cbe 100644
--- a/lib/gitlab/git_access.rb
+++ b/lib/gitlab/git_access.rb
@@ -122,6 +122,11 @@ module Gitlab
       build_status_object(true)
     end
 
+    def can_user_do_action?(action)
+      @permission_cache ||= {}
+      @permission_cache[action] ||= user.can?(action, project)
+    end
+
     def change_access_check(change)
       oldrev, newrev, ref = change.split(' ')
 
@@ -135,7 +140,7 @@ module Gitlab
           :push_code
         end
 
-      unless user.can?(action, project)
+      unless can_user_do_action?(action)
         status =
           case action
           when :force_push_code_to_protected_branches