Wrap Sidekiq scheduler threads in Rails reloader

We execute DB queries in our Sidekiq client middleware so this is needed
to properly checkin DB connections after every poll. On the next poll, a
new connection will be checked out and a connection check query will be
executed. Rails would then handle the reconnection for us in case the
connection is bad.

Without this, we would continue using a bad connection until Sidekiq is
restarted.

Changelog: fixed

config/initializers/sidekiq.rb

@@ -116,3 +116,4 @@ Sidekiq.configure_client do |config|
 end
 
 Sidekiq::Client.prepend Gitlab::Patch::SidekiqClient
+Sidekiq::Cron::Poller.prepend Gitlab::Patch::SidekiqCronPoller

lib/gitlab/patch/sidekiq_cron_poller.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module Patch
+    module SidekiqCronPoller
+      def enqueue
+        Rails.application.reloader.wrap do
+          ::Gitlab::WithRequestStore.with_request_store do
+            super
+          ensure
+            ::Gitlab::Database::LoadBalancing.release_hosts
+          end
+        end
+      end
+    end
+  end
+end

lib/gitlab/sidekiq_enq.rb

@@ -14,10 +14,17 @@ module Gitlab
     LUA_ZPOPBYSCORE_SHA = Digest::SHA1.hexdigest(LUA_ZPOPBYSCORE)
 
     def enqueue_jobs(now = Time.now.to_f.to_s, sorted_sets = Sidekiq::Scheduled::SETS)
-      if Feature.enabled?(:atomic_sidekiq_scheduler, default_enabled: :yaml)
-        atomic_find_jobs_and_enqueue(now, sorted_sets)
-      else
-        find_jobs_and_enqueue(now, sorted_sets)
+      Rails.application.reloader.wrap do
+        ::Gitlab::WithRequestStore.with_request_store do
+          if Feature.enabled?(:atomic_sidekiq_scheduler, default_enabled: :yaml)
+            atomic_find_jobs_and_enqueue(now, sorted_sets)
+          else
+            find_jobs_and_enqueue(now, sorted_sets)
+          end
+
+        ensure
+          ::Gitlab::Database::LoadBalancing.release_hosts
+        end
       end
     end