Merge branch 'fix/sm/atomic-migration' into 'master'

Fix migrate! method (Minimal fix with ExclusiveLock to prevent race conditions)

Closes #4928 and #4980

See merge request gitlab-org/gitlab-ee!4624

app/uploaders/records_uploads.rb

@@ -24,8 +24,7 @@ module RecordsUploads
         uploads.where(path: upload_path).delete_all
         upload.destroy! if upload
-        self.upload = build_upload
-        upload.save!
+        self.upload = build_upload.tap(&:save!)
       end
     end

ee/app/uploaders/object_storage.rb

@@ -61,6 +61,39 @@ module ObjectStorage
     end
   end
+  # Add support for automatic background uploading after the file is stored.
+  #
+  module BackgroundMove
+    extend ActiveSupport::Concern
+
+    def background_upload(mount_points = [])
+      return unless mount_points.any?
+
+      run_after_commit do
+        mount_points.each { |mount| send(mount).schedule_background_upload } # rubocop:disable GitlabSecurity/PublicSend
+      end
+    end
+
+    def changed_mounts
+      self.class.uploaders.select do |mount, uploader_class|
+        mounted_as = uploader_class.serialization_column(self.class, mount)
+        uploader = send(:"#{mounted_as}") # rubocop:disable GitlabSecurity/PublicSend
+
+        next unless uploader
+        next unless uploader.exists?
+        next unless send(:"#{mounted_as}_changed?") # rubocop:disable GitlabSecurity/PublicSend
+
+        mount
+      end.keys
+    end
+
+    included do
+      after_save on: [:create, :update] do
+        background_upload(changed_mounts)
+      end
+    end
+  end
+
   module Concern
     extend ActiveSupport::Concern
@@ -127,7 +160,7 @@ module ObjectStorage
       return unless persist_object_store?
       updated = model.update_column(store_serialization_column, object_store)
-      raise ActiveRecordError unless updated
+      raise 'Failed to update object store' unless updated
     end
     def use_file
@@ -153,32 +186,12 @@ module ObjectStorage
     #   new_store: Enum (Store::LOCAL, Store::REMOTE)
     #
     def migrate!(new_store)
-      return unless object_store != new_store
-      return unless file
-      new_file = nil
-      file_to_delete = file
-      from_object_store = object_store
-      self.object_store = new_store # changes the storage and file
-
-      cache_stored_file! if file_storage?
-
-      with_callbacks(:migrate, file_to_delete) do
-        with_callbacks(:store, file_to_delete) do # for #store_versions!
-          new_file = storage.store!(file)
-          persist_object_store!
-          self.file = new_file
-        end
-      end
-
-      file
-    rescue => e
-      # in case of failure delete new file
-      new_file.delete unless new_file.nil?
-      # revert back to the old file
-      self.object_store = from_object_store
-      self.file = file_to_delete
-      raise e
+      uuid = Gitlab::ExclusiveLease.new(exclusive_lease_key, timeout: 1.hour.to_i).try_obtain
+      raise 'Already running' unless uuid
+      unsafe_migrate!(new_store)
+    ensure
+      Gitlab::ExclusiveLease.cancel(exclusive_lease_key, uuid)
     end
     def schedule_migration_to_object_storage(*args)
@@ -261,5 +274,43 @@ module ObjectStorage
         raise UnknownStoreError
       end
     end
+
+    def exclusive_lease_key
+      "object_storage_migrate:#{model.class}:#{model.id}"
+    end
+
+    #
+    # Move the file to another store
+    #
+    #   new_store: Enum (Store::LOCAL, Store::REMOTE)
+    #
+    def unsafe_migrate!(new_store)
+      return unless object_store != new_store
+      return unless file
+
+      new_file = nil
+      file_to_delete = file
+      from_object_store = object_store
+      self.object_store = new_store # changes the storage and file
+
+      cache_stored_file! if file_storage?
+
+      with_callbacks(:migrate, file_to_delete) do
+        with_callbacks(:store, file_to_delete) do # for #store_versions!
+          new_file = storage.store!(file)
+          persist_object_store!
+          self.file = new_file
+        end
+      end
+
+      file
+    rescue => e
+      # in case of failure delete new file
+      new_file.delete unless new_file.nil?
+      # revert back to the old file
+      self.object_store = from_object_store
+      self.file = file_to_delete
+      raise e
+    end
   end
 end

spec/ee/spec/models/ee/lfs_object_spec.rb

@@ -61,10 +61,24 @@ describe LfsObject do
           end
           it 'schedules the model for migration' do
-            expect(ObjectStorageUploadWorker).to receive(:perform_async).with('LfsObjectUploader', described_class.name, :file, kind_of(Numeric))
+            expect(ObjectStorage::BackgroundMoveWorker)
+              .to receive(:perform_async)
+              .with('LfsObjectUploader', described_class.name, :file, kind_of(Numeric))
+              .once
             subject
           end
+
+          it 'schedules the model for migration once' do
+            expect(ObjectStorage::BackgroundMoveWorker)
+              .to receive(:perform_async)
+              .with('LfsObjectUploader', described_class.name, :file, kind_of(Numeric))
+              .once
+
+            lfs_object = create(:lfs_object)
+            lfs_object.file = fixture_file_upload(Rails.root + "spec/fixtures/dk.png", "`/png")
+            lfs_object.save!
+          end
         end
         context 'when is unlicensed' do

spec/requests/lfs_http_spec.rb

@@ -997,7 +997,7 @@ describe 'Git LFS API and storage' do
           context 'and workhorse requests upload finalize for a new lfs object' do
             before do
-              allow_any_instance_of(LfsObjectUploader).to receive(:exists?) { false }
+              lfs_object.destroy
             end
             context 'with object storage disabled' do

spec/support/shared_examples/uploaders/object_storage_shared_examples.rb

@@ -20,6 +20,19 @@ shared_examples "migrates" do |to_store:, from_store: nil|
     migrate(from)
   end
+  it 'returns corresponding file type' do
+    expect(subject).to be_an(CarrierWave::Uploader::Base)
+    expect(subject).to be_a(ObjectStorage::Concern)
+
+    if from == described_class::Store::REMOTE
+      expect(subject.file).to be_a(CarrierWave::Storage::Fog::File)
+    elsif from == described_class::Store::LOCAL
+      expect(subject.file).to be_a(CarrierWave::SanitizedFile)
+    else
+      raise 'Unexpected file type'
+    end
+  end
+
   it 'does nothing when migrating to the current store' do
     expect { migrate(from) }.not_to change { subject.object_store }.from(from)
   end
@@ -38,6 +51,42 @@ shared_examples "migrates" do |to_store:, from_store: nil|
     expect(File.exist?(original_file)).to be_falsey
   end
+  it 'can access to the original file during migration' do
+    file = subject.file
+
+    allow(subject).to receive(:delete_migrated_file) { } # Remove as a callback of :migrate
+    allow(subject).to receive(:record_upload) { } # Remove as a callback of :store (:record_upload)
+
+    expect(file.exists?).to be_truthy
+    expect { migrate(to) }.not_to change { file.exists? }
+  end
+
+  context 'when migrate! is not oqqupied by another process' do
+    it 'executes migrate!' do
+      expect(subject).to receive(:object_store=).at_least(1)
+
+      migrate(to)
+    end
+  end
+
+  context 'when migrate! is occupied by another process' do
+    let(:exclusive_lease_key) { "object_storage_migrate:#{subject.model.class}:#{subject.model.id}" }
+
+    before do
+      @uuid = Gitlab::ExclusiveLease.new(exclusive_lease_key, timeout: 1.hour.to_i).try_obtain
+    end
+
+    it 'does not execute migrate!' do
+      expect(subject).not_to receive(:unsafe_migrate!)
+
+      expect { migrate(to) }.to raise_error('Already running')
+    end
+
+    after do
+      Gitlab::ExclusiveLease.cancel(exclusive_lease_key, @uuid)
+    end
+  end
+
   context 'migration is unsuccessful' do
     shared_examples "handles gracefully" do |error:|
       it 'does not update the object_store' do

spec/uploaders/job_artifact_uploader_spec.rb

@@ -67,4 +67,14 @@ describe JobArtifactUploader do
     it { is_expected.to include("/#{job_artifact.job_id}/#{job_artifact.id}/") }
     it { is_expected.to end_with("ci_build_artifacts.zip") }
   end
+
+  describe "#migrate!" do
+    before do
+      uploader.store!(fixture_file_upload(Rails.root.join('spec/fixtures/trace/sample_trace')))
+      stub_artifacts_object_storage
+    end
+
+    it_behaves_like "migrates", to_store: described_class::Store::REMOTE
+    it_behaves_like "migrates", from_store: described_class::Store::REMOTE, to_store: described_class::Store::LOCAL
+  end
 end

spec/uploaders/object_storage_spec.rb

@@ -128,6 +128,33 @@ describe ObjectStorage do
         expect(uploader.object_store).to eq(uploader.upload.store)
       end
     end
+
+    describe '#migrate!' do
+      let(:new_store) { ObjectStorage::Store::REMOTE }
+
+      before do
+        stub_uploads_object_storage(uploader: AvatarUploader)
+      end
+
+      subject { uploader.migrate!(new_store) }
+
+      it 'persist @object_store to the recorded upload' do
+        subject
+
+        expect(uploader.upload.store).to eq(new_store)
+      end
+
+      describe 'fails' do
+        it 'is handled gracefully' do
+          store = uploader.object_store
+          expect_any_instance_of(Upload).to receive(:save!).and_raise("An error")
+
+          expect { subject }.to raise_error("An error")
+          expect(uploader.exists?).to be_truthy
+          expect(uploader.upload.store).to eq(store)
+        end
+      end
+    end
   end
   # this means the model holds an <mounted_as>_store attribute directly