Add the ability to perform background migrations

Background migrations can be used to perform long running data
migrations without these blocking a deployment procedure.

See MR https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/11854 for
more information.

1 files changed, 48 insertions, 0 deletions

diff --git a/spec/lib/gitlab/background_migration_spec.rb b/spec/lib/gitlab/background_migration_spec.rb
new file mode 100644
index 00000000000..f2073b9bcb3
--- /dev/null
+++ b/spec/lib/gitlab/background_migration_spec.rb
@@ -0,0 +1,48 @@
+require 'spec_helper'
+
+describe Gitlab::BackgroundMigration do
+  describe '.steal' do
+    it 'steals jobs from a queue' do
+      queue = [double(:job, args: ['Foo', [10, 20]])]
+
+      allow(Sidekiq::Queue).to receive(:new).
+        with(BackgroundMigrationWorker.sidekiq_options['queue']).
+        and_return(queue)
+
+      expect(queue[0]).to receive(:delete)
+
+      expect(described_class).to receive(:perform).with('Foo', [10, 20])
+
+      described_class.steal('Foo')
+    end
+
+    it 'does not steal jobs for a different migration' do
+      queue = [double(:job, args: ['Foo', [10, 20]])]
+
+      allow(Sidekiq::Queue).to receive(:new).
+        with(BackgroundMigrationWorker.sidekiq_options['queue']).
+        and_return(queue)
+
+      expect(described_class).not_to receive(:perform)
+
+      expect(queue[0]).not_to receive(:delete)
+
+      described_class.steal('Bar')
+    end
+  end
+
+  describe '.perform' do
+    it 'performs a background migration' do
+      instance = double(:instance)
+      klass = double(:klass, new: instance)
+
+      expect(described_class).to receive(:const_get).
+        with('Foo').
+        and_return(klass)
+
+      expect(instance).to receive(:perform).with(10, 20)
+
+      described_class.perform('Foo', [10, 20])
+    end
+  end
+end