process page views in parallel for multiple shards

Change-Id: Ief4bb4e51248ad1bc005522735b52c6329b7c50d
Reviewed-on: https://gerrit.instructure.com/11246
Reviewed-by: Zach Wily <zach@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>

config/periodic_jobs.rb

@@ -73,7 +73,7 @@ if PageView.page_view_method == :cache
   # periodically pull new page views off the cache and insert them into the db
   Delayed::Periodic.cron 'PageView.process_cache_queue', '*/1 * * * *' do
     Shard.with_each_shard do
-      PageView.process_cache_queue
+      PageView.send_later_enqueue_args(:process_cache_queue, :singleton => "PageView.process_cache_queue:#{Shard.current.description}")
     end
   end
 end

lib/stubs/shard.rb

@@ -49,6 +49,10 @@ class Shard
     {}
   end
 
+  def description
+    "default"
+  end
+
   yaml_as "tag:instructure.com,2012:Shard"
 
   def self.yaml_new(klass, tag, val)