Merge branch 'fix_redis_inheritederror' into 'master'

Fix Redis::InheritedError

This was hand-tested against 7.5.2-ee.

A proper solution would be to update Sidetiq to 0.6.3 or newer but
that requires first upgrading Sidekiq to 3.x.

See merge request !260

CHANGELOG-EE

@@ -2,6 +2,9 @@ v 7.6.0
   - Added Audit events related to membership changes for groups and projects
   - Added option to attempt a rebase before merging merge request
 
+v 7.5.3
+  - Only set up Sidetiq from a Sidekiq server process (fixes Redis::InheritedError)
+
 v 7.5.0
   - Added an ability to check each author commit's email by regex
   - Added an ability to restrict commit authors to existing Gitlab users

app/workers/ldap_sync_worker.rb

@@ -2,7 +2,9 @@ class LdapSyncWorker
   include Sidekiq::Worker
   include Sidetiq::Schedulable
 
-  if Gitlab.config.ldap.enabled
+  # We check if we are in a Sidekiq server process because of a bug in Sidetiq
+  # 0.6.1 which was giving Unicorn trouble (throwing a Redis::InheritedError).
+  if Gitlab.config.ldap.enabled && Sidekiq.server?
     HOUR = Gitlab.config.ldap.schedule_sync_hour
     MINUTE = Gitlab.config.ldap.schedule_sync_minute