Merge branch 'fix/gb/process-scheduled-background-migrations' into 'master'

Process scheduled background migrations as well

Closes #34951

See merge request !12787

lib/gitlab/background_migration.rb

 module Gitlab
   module BackgroundMigration
+    def self.queue
+      @queue ||= BackgroundMigrationWorker.sidekiq_options['queue']
+    end
+
     # Begins stealing jobs from the background migrations queue, blocking the
     # caller until all jobs have been completed.
     #
+    # When a migration raises a StandardError is is going to be retries up to
+    # three times, for example, to recover from a deadlock.
+    #
+    # When Exception is being raised, it enqueues the migration again, and
+    # re-raises the exception.
+    #
     # steal_class - The name of the class for which to steal jobs.
     def self.steal(steal_class)
-      queue = Sidekiq::Queue
-        .new(BackgroundMigrationWorker.sidekiq_options['queue'])
+      enqueued = Sidekiq::Queue.new(self.queue)
+      scheduled = Sidekiq::ScheduledSet.new
 
+      [scheduled, enqueued].each do |queue|
         queue.each do |job|
           migration_class, migration_args = job.args
 
+          next unless job.queue == self.queue
           next unless migration_class == steal_class
 
-        perform(migration_class, migration_args)
+          begin
+            perform(migration_class, migration_args, retries: 3) if job.delete
+          rescue Exception # rubocop:disable Lint/RescueException
+            BackgroundMigrationWorker # enqueue this migration again
+              .perform_async(migration_class, migration_args)
 
-        job.delete
+            raise
+          end
+        end
       end
     end
 
+    ##
+    # Performs a background migration.
+    #
     # class_name - The name of the background migration class as defined in the
     #              Gitlab::BackgroundMigration namespace.
     #

spec/lib/gitlab/background_migration_spec.rb

 require 'spec_helper'
 
 describe Gitlab::BackgroundMigration do
+  describe '.queue' do
+    it 'returns background migration worker queue' do
+      expect(described_class.queue)
+        .to eq BackgroundMigrationWorker.sidekiq_options['queue']
+    end
+  end
+
   describe '.steal' do
-    it 'steals jobs from a queue' do
-      queue = [double(:job, args: ['Foo', [10, 20]])]
+    context 'when there are enqueued jobs present' do
+      let(:queue) do
+        [double(args: ['Foo', [10, 20]], queue: described_class.queue)]
+      end
 
+      before do
         allow(Sidekiq::Queue).to receive(:new)
-        .with(BackgroundMigrationWorker.sidekiq_options['queue'])
+          .with(described_class.queue)
           .and_return(queue)
+      end
 
-      expect(queue[0]).to receive(:delete)
+      context 'when queue contains unprocessed jobs' do
+        it 'steals jobs from a queue' do
+          expect(queue[0]).to receive(:delete).and_return(true)
 
-      expect(described_class).to receive(:perform).with('Foo', [10, 20])
+          expect(described_class).to receive(:perform)
+            .with('Foo', [10, 20], anything)
 
           described_class.steal('Foo')
         end
 
-    it 'does not steal jobs for a different migration' do
-      queue = [double(:job, args: ['Foo', [10, 20]])]
+        it 'does not steal job that has already been taken' do
+          expect(queue[0]).to receive(:delete).and_return(false)
 
-      allow(Sidekiq::Queue).to receive(:new)
-        .with(BackgroundMigrationWorker.sidekiq_options['queue'])
-        .and_return(queue)
+          expect(described_class).not_to receive(:perform)
 
+          described_class.steal('Foo')
+        end
+
+        it 'does not steal jobs for a different migration' do
           expect(described_class).not_to receive(:perform)
 
           expect(queue[0]).not_to receive(:delete)
@@ -31,16 +47,74 @@ describe Gitlab::BackgroundMigration do
         end
       end
 
+      context 'when one of the jobs raises an error' do
+        let(:migration) { spy(:migration) }
+
+        let(:queue) do
+          [double(args: ['Foo', [10, 20]], queue: described_class.queue),
+           double(args: ['Foo', [20, 30]], queue: described_class.queue)]
+        end
+
+        before do
+          stub_const("#{described_class}::Foo", migration)
+
+          allow(queue[0]).to receive(:delete).and_return(true)
+          allow(queue[1]).to receive(:delete).and_return(true)
+        end
+
+        it 'enqueues the migration again and re-raises the error' do
+          allow(migration).to receive(:perform).with(10, 20)
+            .and_raise(Exception, 'Migration error').once
+
+          expect(BackgroundMigrationWorker).to receive(:perform_async)
+            .with('Foo', [10, 20]).once
+
+          expect { described_class.steal('Foo') }.to raise_error(Exception)
+        end
+      end
+    end
+
+    context 'when there are scheduled jobs present', :sidekiq, :redis do
+      it 'steals all jobs from the scheduled sets' do
+        Sidekiq::Testing.disable! do
+          BackgroundMigrationWorker.perform_in(10.minutes, 'Object')
+
+          expect(Sidekiq::ScheduledSet.new).to be_one
+          expect(described_class).to receive(:perform).with('Object', any_args)
+
+          described_class.steal('Object')
+
+          expect(Sidekiq::ScheduledSet.new).to be_none
+        end
+      end
+    end
+
+    context 'when there are enqueued and scheduled jobs present', :sidekiq, :redis do
+      it 'steals from the scheduled sets queue first' do
+        Sidekiq::Testing.disable! do
+          expect(described_class).to receive(:perform)
+            .with('Object', [1], anything).ordered
+          expect(described_class).to receive(:perform)
+            .with('Object', [2], anything).ordered
+
+          BackgroundMigrationWorker.perform_async('Object', [2])
+          BackgroundMigrationWorker.perform_in(10.minutes, 'Object', [1])
+
+          described_class.steal('Object')
+        end
+      end
+    end
+  end
+
   describe '.perform' do
-    it 'performs a background migration' do
-      instance = double(:instance)
-      klass = double(:klass, new: instance)
+    let(:migration) { spy(:migration) }
 
-      expect(described_class).to receive(:const_get)
-        .with('Foo')
-        .and_return(klass)
+    before do
+      stub_const("#{described_class.name}::Foo", migration)
+    end
 
-      expect(instance).to receive(:perform).with(10, 20)
+    it 'performs a background migration' do
+      expect(migration).to receive(:perform).with(10, 20).once
 
       described_class.perform('Foo', [10, 20])
     end

spec/support/sidekiq.rb

@@ -8,4 +8,8 @@ RSpec.configure do |config|
   config.after(:each, :sidekiq) do
     Sidekiq::Worker.clear_all
   end
+
+  config.after(:each, :sidekiq, :redis) do
+    Sidekiq.redis { |redis| redis.flushdb }
+  end
 end