Convert migrations to generate subkeys to a background migration

db/post_migrate/20171005130944_schedule_create_gpg_key_subkeys_from_gpg_keys.rb

+# See http://doc.gitlab.com/ce/development/migration_style_guide.html
+# for more information on how to write migrations for GitLab.
+
+class ScheduleCreateGpgKeySubkeysFromGpgKeys < ActiveRecord::Migration
+  disable_ddl_transaction!
+
+  DOWNTIME = false
+
+  class GpgKey < ActiveRecord::Base
+    self.table_name = 'gpg_keys'
+  end
+
+  def up
+    GpgKey.select(:id).in_batches do |relation|
+      jobs = relation.pluck(:id).map do |id|
+        ['CreateGpgKeySubkeysFromGpgKeys', [id]]
+      end
+
+      BackgroundMigrationWorker.perform_bulk(jobs)
+    end
+  end
+
+  def down
+  end
+end

db/schema.rb

@@ -11,7 +11,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema.define(version: 20171004121444) do
+ActiveRecord::Schema.define(version: 20171005130944) do
 
   # These are extensions that must be enabled in order to support this database
   enable_extension "plpgsql"

db/post_migrate/20171002161539_create_gpg_key_subkeys_for_existing_gpg_keys.rb → lib/gitlab/background_migration/create_gpg_key_subkeys_from_gpg_keys.rb

-# See http://doc.gitlab.com/ce/development/migration_style_guide.html
-# for more information on how to write migrations for GitLab.
-
-class CreateGpgKeySubkeysForExistingGpgKeys < ActiveRecord::Migration
-  disable_ddl_transaction!
-
-  DOWNTIME = false
-
+class Gitlab::BackgroundMigration::CreateGpgKeySubkeysFromGpgKeys
   class GpgKey < ActiveRecord::Base
     self.table_name = 'gpg_keys'
 
@@ -27,17 +20,13 @@ class CreateGpgKeySubkeysForExistingGpgKeys < ActiveRecord::Migration
     sha_attribute :fingerprint
   end
 
-  def up
-    GpgKey.with_subkeys.each_batch do |batch|
-      batch.each do |gpg_key|
-        next if gpg_key.subkeys.any?
+  def perform(gpg_key_id)
+    gpg_key = GpgKey.find_by(id: gpg_key_id)
 
-        create_subkeys(gpg_key) && update_signatures(gpg_key)
-      end
-    end
-  end
+    return if gpg_key.nil?
+    return if gpg_key.subkeys.any?
 
-  def down
+    create_subkeys(gpg_key) && update_signatures(gpg_key)
   end
 
   private