1 files changed, 60 insertions, 0 deletions
diff --git a/lib/gitlab/database/background_migration/scheduler.rb b/lib/gitlab/database/background_migration/scheduler.rb
new file mode 100644
index 00000000000..5f8a5ec06a5
--- /dev/null
+++ b/lib/gitlab/database/background_migration/scheduler.rb
@@ -0,0 +1,60 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Database
+    module BackgroundMigration
+      class Scheduler
+        def perform(migration_wrapper: BatchedMigrationWrapper.new)
+          active_migration = BatchedMigration.active.queue_order.first
+
+          return unless active_migration&.interval_elapsed?
+
+          if next_batched_job = create_next_batched_job!(active_migration)
+            migration_wrapper.perform(next_batched_job)
+          else
+            finish_active_migration(active_migration)
+          end
+        end
+
+        private
+
+        def create_next_batched_job!(active_migration)
+          next_batch_range = find_next_batch_range(active_migration)
+
+          return if next_batch_range.nil?
+
+          active_migration.create_batched_job!(next_batch_range.min, next_batch_range.max)
+        end
+
+        def find_next_batch_range(active_migration)
+          batching_strategy = active_migration.batch_class.new
+          batch_min_value = active_migration.next_min_value
+
+          next_batch_bounds = batching_strategy.next_batch(
+            active_migration.table_name,
+            active_migration.column_name,
+            batch_min_value: batch_min_value,
+            batch_size: active_migration.batch_size)
+
+          return if next_batch_bounds.nil?
+
+          clamped_batch_range(active_migration, next_batch_bounds)
+        end
+
+        def clamped_batch_range(active_migration, next_bounds)
+          min_value, max_value = next_bounds
+
+          return if min_value > active_migration.max_value
+
+          max_value = max_value.clamp(min_value, active_migration.max_value)
+
+          (min_value..max_value)
+        end
+
+        def finish_active_migration(active_migration)
+          active_migration.finished!
+        end
+      end
+    end
+  end
+end