Update diego sync to not fetch every bit of every object, only completely fetch objects that need syncing

lib/cloud_controller/diego/processes_sync.rb

@@ -21,35 +21,24 @@ def sync
         @bump_freshness = true
         diego_lrps = bbs_apps_client.fetch_scheduling_infos.index_by { |d| d.desired_lrp_key.process_guid }
         logger.info('fetched-scheduling-infos')
-
-        batched_processes do |processes|
+        to_desire = []
+        to_update = {}
+        batched_processes_for_sync do |processes|
           processes.each do |process|
             process_guid = ProcessGuid.from_process(process)
             diego_lrp    = diego_lrps.delete(process_guid)
 
             if diego_lrp.nil?
-              workpool.submit(process) do |p|
-                logger.info('desiring-lrp', process_guid: p.guid, app_guid: p.app_guid)
-                bbs_apps_client.desire_app(p)
-                logger.info('desire-lrp', process_guid: p.guid)
-              end
+              to_desire.append(process.id)
             elsif process.updated_at.to_f.to_s != diego_lrp.annotation
-              workpool.submit(process, diego_lrp) do |p, l|
-                logger.info('updating-lrp', process_guid: p.guid, app_guid: p.app_guid)
-                bbs_apps_client.update_app(p, l)
-                logger.info('update-lrp', process_guid: p.guid)
-              end
+              to_update[process.id] = diego_lrp
             end
           end
         end
 
-        diego_lrps.each_key do |process_guid_to_delete|
-          workpool.submit(process_guid_to_delete) do |guid|
-            logger.info('deleting-lrp', process_guid: guid)
-            bbs_apps_client.stop_app(guid)
-            logger.info('delete-lrp', process_guid: guid)
-          end
-        end
+        update_processes(to_update)
+        desire_processes(to_desire)
+        delete_lrps(diego_lrps)
 
         workpool.drain
 
@@ -95,31 +84,69 @@ def process_workpool_exceptions(exceptions)
         @statsd_updater.update_synced_invalid_lrps(invalid_lrps)
       end
 
+      def update_processes(to_update)
+        batched_processes(to_update.keys) do |processes|
+          processes.each do |process|
+            workpool.submit(process, to_update[process.id]) do |p, l|
+              logger.info('updating-lrp', process_guid: p.guid, app_guid: p.app_guid)
+              bbs_apps_client.update_app(p, l)
+              logger.info('update-lrp', process_guid: p.guid)
+            end
+          end
+        end
+      end
+
+      def desire_processes(to_create)
+        batched_processes(to_create) do |processes|
+          processes.each do |process|
+            workpool.submit(process) do |p|
+              logger.info('desiring-lrp', process_guid: p.guid, app_guid: p.app_guid)
+              bbs_apps_client.desire_app(p)
+              logger.info('desire-lrp', process_guid: p.guid)
+            end
+          end
+        end
+      end
+
+      def delete_lrps(to_delete)
+        to_delete.each_key do |process_guid_to_delete|
+          workpool.submit(process_guid_to_delete) do |guid|
+            logger.info('deleting-lrp', process_guid: guid)
+            bbs_apps_client.stop_app(guid)
+            logger.info('delete-lrp', process_guid: guid)
+          end
+        end
+      end
+
       def formatted_backtrace_from_error(error)
         error.backtrace.present? ? error.backtrace.join("\n") + "\n..." : ''
       end
 
-      def batched_processes
+      def batched_processes_for_sync
         last_id = 0
 
         loop do
-          processes = processes(last_id).all
+          processes = processes_for_sync(last_id).all
           yield processes
           return if processes.count < BATCH_SIZE
 
           last_id = processes.last.id
         end
       end
 
-      def processes(last_id)
+      def batched_processes(ids)
+        ids.each_slice(BATCH_SIZE) do |id_chunk|
+          processes = processes(id_chunk).all
+          yield processes
+        end
+      end
+
+      def processes(ids)
         processes = ProcessModel.
                     diego.
                     runnable.
-                    where(Sequel.lit("#{ProcessModel.table_name}.id > ?", last_id)).
-                    order("#{ProcessModel.table_name}__id".to_sym).
-                    eager(:desired_droplet, :space, :service_bindings, { routes: :domain }, { app: :buildpack_lifecycle_data }).
-                    limit(BATCH_SIZE)
-
+                    where(Sequel.lit("#{ProcessModel.table_name}.id IN ?", ids)).
+                    eager(:desired_droplet, :space, :service_bindings, { routes: :domain }, { app: :buildpack_lifecycle_data })
         if FeatureFlag.enabled?(:diego_docker)
           processes.select_all(ProcessModel.table_name)
         else
@@ -128,6 +155,18 @@ def processes(last_id)
         end
       end
 
+      def processes_for_sync(last_id)
+        processes = ProcessModel.
+                    diego.
+                    runnable.
+                    where(Sequel.lit("#{ProcessModel.table_name}.id > ?", last_id)).
+                    order("#{ProcessModel.table_name}__id".to_sym).
+                    limit(BATCH_SIZE)
+
+        processes.select("#{ProcessModel.table_name}__id".to_sym, "#{ProcessModel.table_name}__guid".to_sym, "#{ProcessModel.table_name}__version".to_sym,
+                         "#{ProcessModel.table_name}__updated_at".to_sym)
+      end
+
       def bbs_apps_client
         CloudController::DependencyLocator.instance.bbs_apps_client
       end