Add rake task to migrate Terraform states to object storage

https://gitlab.com/gitlab-org/gitlab/-/merge_requests/50740

app/models/terraform/state_version.rb

@@ -10,6 +10,7 @@ module Terraform
 
     scope :ordered_by_version_desc, -> { order(version: :desc) }
     scope :with_files_stored_locally, -> { where(file_store: Terraform::StateUploader::Store::LOCAL) }
+    scope :preload_state, -> { includes(:terraform_state) }
 
     default_value_for(:file_store) { StateUploader.default_store }
 

app/uploaders/terraform/state_uploader.rb

@@ -6,6 +6,10 @@ module Terraform
 
     storage_options Gitlab.config.terraform_state
 
+    # TODO: Remove this line
+    # See https://gitlab.com/gitlab-org/gitlab/-/issues/232917
+    alias_method :upload, :model
+
     delegate :terraform_state, :project_id, to: :model
 
     # Use Lockbox to encrypt/decrypt the stored file (registers CarrierWave callbacks)

changelogs/unreleased/terraform-states-migrate-task.yml

+---
+title: Add rake task to migrate Terraform states to object storage
+merge_request: 50740
+author:
+type: added

doc/administration/terraform_state.md

@@ -100,6 +100,11 @@ See [the available connection settings for different providers](object_storage.m
    ```
 
 1. Save the file and [reconfigure GitLab](restart_gitlab.md#omnibus-gitlab-reconfigure) for the changes to take effect.
+1. Migrate any existing local states to the object storage (GitLab 13.9 and later):
+
+   ```shell
+   gitlab-rake gitlab:terraform_states:migrate
+   ```
 
 **In installations from source:**
 
@@ -120,3 +125,8 @@ See [the available connection settings for different providers](object_storage.m
    ```
 
 1. Save the file and [restart GitLab](restart_gitlab.md#installations-from-source) for the changes to take effect.
+1. Migrate any existing local states to the object storage (GitLab 13.9 and later):
+
+   ```shell
+   sudo -u git -H bundle exec rake gitlab:terraform_states:migrate RAILS_ENV=production
+   ```

lib/gitlab/terraform/state_migration_helper.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module Terraform
+    class StateMigrationHelper
+      class << self
+        def migrate_to_remote_storage(&block)
+          migrate_in_batches(
+            ::Terraform::StateVersion.with_files_stored_locally.preload_state,
+            ::Terraform::StateUploader::Store::REMOTE,
+            &block
+          )
+        end
+
+        private
+
+        def batch_size
+          ENV.fetch('MIGRATION_BATCH_SIZE', 10).to_i
+        end
+
+        def migrate_in_batches(versions, store, &block)
+          versions.find_each(batch_size: batch_size) do |version| # rubocop:disable CodeReuse/ActiveRecord
+            version.file.migrate!(store)
+
+            yield version if block_given?
+          end
+        end
+      end
+    end
+  end
+end

lib/tasks/gitlab/terraform/migrate.rake

+# frozen_string_literal: true
+
+require 'logger'
+
+desc "GitLab | Terraform | Migrate Terraform states to remote storage"
+namespace :gitlab do
+  namespace :terraform_states do
+    task migrate: :environment do
+      logger = Logger.new(STDOUT)
+      logger.info('Starting transfer of Terraform states to object storage')
+
+      begin
+        Gitlab::Terraform::StateMigrationHelper.migrate_to_remote_storage do |state_version|
+          message = "Transferred Terraform state version ID #{state_version.id} (#{state_version.terraform_state.name}/#{state_version.version}) to object storage"
+
+          logger.info(message)
+        end
+      rescue => e
+        logger.error("Failed to migrate: #{e.message}")
+      end
+    end
+  end
+end

spec/lib/gitlab/terraform/state_migration_helper_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Gitlab::Terraform::StateMigrationHelper do
+  before do
+    stub_terraform_state_object_storage
+  end
+
+  describe '.migrate_to_remote_storage' do
+    let!(:local_version) { create(:terraform_state_version, file_store: Terraform::StateUploader::Store::LOCAL) }
+
+    subject { described_class.migrate_to_remote_storage }
+
+    it 'migrates remote files to remote storage' do
+      subject
+
+      expect(local_version.reload.file_store).to eq(Terraform::StateUploader::Store::REMOTE)
+    end
+  end
+end

spec/tasks/gitlab/terraform/migrate_rake_spec.rb

+# frozen_string_literal: true
+
+require 'rake_helper'
+
+RSpec.describe 'gitlab:terraform_states' do
+  let_it_be(:version) { create(:terraform_state_version) }
+
+  let(:logger) { instance_double(Logger) }
+  let(:helper) { double }
+
+  before(:all) do
+    Rake.application.rake_require 'tasks/gitlab/terraform/migrate'
+  end
+
+  before do
+    allow(Logger).to receive(:new).with(STDOUT).and_return(logger)
+  end
+
+  describe 'gitlab:terraform_states:migrate' do
+    subject { run_rake_task('gitlab:terraform_states:migrate') }
+
+    it 'invokes the migration helper to move files to object storage' do
+      expect(Gitlab::Terraform::StateMigrationHelper).to receive(:migrate_to_remote_storage).and_yield(version)
+      expect(logger).to receive(:info).with('Starting transfer of Terraform states to object storage')
+      expect(logger).to receive(:info).with(/Transferred Terraform state version ID #{version.id}/)
+
+      subject
+    end
+
+    context 'an error is raised while migrating' do
+      let(:error_message) { 'Something went wrong' }
+
+      before do
+        allow(Gitlab::Terraform::StateMigrationHelper).to receive(:migrate_to_remote_storage).and_raise(StandardError, error_message)
+      end
+
+      it 'logs the error' do
+        expect(logger).to receive(:info).with('Starting transfer of Terraform states to object storage')
+        expect(logger).to receive(:error).with("Failed to migrate: #{error_message}")
+
+        subject
+      end
+    end
+  end
+end