Improve reliability of LdapSyncWorker

First of all, Sidekiq job retries are not needed because this is a
recurring job. Second of all, we add the option to run once every
X days instead of once every day. This helps when the job takes
close to or more than 24 hours to complete.

app/workers/ldap_sync_worker.rb

@@ -2,11 +2,14 @@ class LdapSyncWorker
   include Sidekiq::Worker
   include Sidetiq::Schedulable
+  sidekiq_options retry: false
+
   if Gitlab.config.ldap.enabled
+    DAILY = Gitlab.config.ldap.schedule_sync_daily
     HOUR = Gitlab.config.ldap.schedule_sync_hour
     MINUTE = Gitlab.config.ldap.schedule_sync_minute
-    recurrence { daily.hour_of_day(HOUR).minute_of_hour(MINUTE) }
+    recurrence { daily(DAILY).hour_of_day(HOUR).minute_of_hour(MINUTE) }
   end
   def perform

config/gitlab.yml.example

@@ -168,6 +168,7 @@ production: &base
     # In addition to refreshing users when they log in,
     # enabling this setting will refresh LDAP user membership once a day.
     # Default time of the day when this will happen is at 1:30am server time.
+    schedule_sync_daily: 1 # Run once every X days. Default: 1, meaning 'daily'
     schedule_sync_hour: 1 # Hour of the day. Value from 0-23.
     schedule_sync_minute: 30 # Minute of the hour. Value from 0-59.

config/initializers/1_settings.rb

@@ -92,6 +92,7 @@ end
 Settings['ldap'] ||= Settingslogic.new({})
 Settings.ldap['enabled'] = false if Settings.ldap['enabled'].nil?
 Settings.ldap['sync_time'] = 3600 if Settings.ldap['sync_time'].nil?
+Settings.ldap['schedule_sync_daily'] = 1 if Settings.ldap['schedule_sync_daily'].nil?
 Settings.ldap['schedule_sync_hour'] = 1 if Settings.ldap['schedule_sync_hour'].nil?
 Settings.ldap['schedule_sync_minute'] = 30  if Settings.ldap['schedule_sync_minute'].nil?