From 3d1690c77625fbbfa5c0ec28aeabc9702c5dfb05 Mon Sep 17 00:00:00 2001
From: Nick Thomas <nick@gitlab.com>
Date: Tue, 13 Nov 2018 20:41:45 +0000
Subject: [PATCH] Fix a race condition intermittently breaking GitLab startup

---
 app/models/shard.rb                             | 11 +++++------
 changelogs/unreleased/53972-fix-fill-shards.yml |  5 +++++
 2 files changed, 10 insertions(+), 6 deletions(-)
 create mode 100644 changelogs/unreleased/53972-fix-fill-shards.yml

diff --git a/app/models/shard.rb b/app/models/shard.rb
index 2fa22bd040c..2e75bc91df0 100644
--- a/app/models/shard.rb
+++ b/app/models/shard.rb
@@ -9,13 +9,12 @@ class Shard < ActiveRecord::Base
 
     # The GitLab config does not change for the lifecycle of the process
     in_config = Gitlab.config.repositories.storages.keys.map(&:to_s)
+    in_db = all.pluck(:name)
 
-    transaction do
-      in_db = all.pluck(:name)
-      missing = in_config - in_db
-
-      missing.map { |name| by_name(name) }
-    end
+    # This may race with other processes creating shards at the same time, but
+    # `by_name` will handle that correctly
+    missing = in_config - in_db
+    missing.map { |name| by_name(name) }
   end
 
   def self.by_name(name)
diff --git a/changelogs/unreleased/53972-fix-fill-shards.yml b/changelogs/unreleased/53972-fix-fill-shards.yml
new file mode 100644
index 00000000000..ca94d6cc589
--- /dev/null
+++ b/changelogs/unreleased/53972-fix-fill-shards.yml
@@ -0,0 +1,5 @@
+---
+title: Fix a race condition intermittently breaking GitLab startup
+merge_request: 23028
+author:
+type: fixed