Create a diff deletion worker scheduler to avoid long-running post-migration

1 files changed, 32 insertions, 0 deletions

diff --git a/lib/gitlab/background_migration/schedule_diff_files_deletion.rb b/lib/gitlab/background_migration/schedule_diff_files_deletion.rb
new file mode 100644
index 00000000000..d944ed90fce
--- /dev/null
+++ b/lib/gitlab/background_migration/schedule_diff_files_deletion.rb
@@ -0,0 +1,32 @@
+# frozen_string_literal: true
+# rubocop:disable Metrics/AbcSize
+# rubocop:disable Style/Documentation
+
+module Gitlab
+  module BackgroundMigration
+    class ScheduleDiffFilesDeletion
+      BATCH_SIZE = 5
+      MIGRATION = 'DeleteDiffFiles'
+      DELAY_INTERVAL = 10.minutes
+
+      def perform(diff_ids, scheduler_index)
+        relation = MergeRequestDiff.where(id: diff_ids)
+
+        job_batches = relation.pluck(:id).in_groups_of(BATCH_SIZE, false).map do |ids|
+          ids.map { |id| [MIGRATION, [id]] }
+        end
+
+        job_batches.each_with_index do |jobs, inner_index|
+          # This will give some space between batches of workers.
+          interval = DELAY_INTERVAL * scheduler_index + inner_index.minutes
+
+          # A single `merge_request_diff` can be associated with way too many
+          # `merge_request_diff_files`. It's better to avoid scheduling big
+          # batches and go with 5 at a time.
+          #
+          BackgroundMigrationWorker.bulk_perform_in(interval, jobs)
+        end
+      end
+    end
+  end
+end