1 files changed, 79 insertions, 0 deletions
diff --git a/app/services/pages/migrate_from_legacy_storage_service.rb b/app/services/pages/migrate_from_legacy_storage_service.rb
new file mode 100644
index 00000000000..9b36b3f11b4
--- /dev/null
+++ b/app/services/pages/migrate_from_legacy_storage_service.rb
@@ -0,0 +1,79 @@
+# frozen_string_literal: true
+
+module Pages
+  class MigrateFromLegacyStorageService
+    def initialize(logger, migration_threads:, batch_size:, ignore_invalid_entries:)
+      @logger = logger
+      @migration_threads = migration_threads
+      @batch_size = batch_size
+      @ignore_invalid_entries = ignore_invalid_entries
+
+      @migrated = 0
+      @errored = 0
+      @counters_lock = Mutex.new
+    end
+
+    def execute
+      @queue = SizedQueue.new(1)
+
+      threads = start_migration_threads
+
+      ProjectPagesMetadatum.only_on_legacy_storage.each_batch(of: @batch_size) do |batch|
+        @queue.push(batch)
+      end
+
+      @queue.close
+
+      @logger.info("Waiting for threads to finish...")
+      threads.each(&:join)
+
+      { migrated: @migrated, errored: @errored }
+    end
+
+    def start_migration_threads
+      Array.new(@migration_threads) do
+        Thread.new do
+          while batch = @queue.pop
+            Rails.application.executor.wrap do
+              process_batch(batch)
+            end
+          end
+        end
+      end
+    end
+
+    def process_batch(batch)
+      batch.with_project_route_and_deployment.each do |metadatum|
+        project = metadatum.project
+
+        migrate_project(project)
+      end
+
+      @logger.info("#{@migrated} projects are migrated successfully, #{@errored} projects failed to be migrated")
+    rescue => e
+      # This method should never raise exception otherwise all threads might be killed
+      # and this will result in queue starving (and deadlock)
+      Gitlab::ErrorTracking.track_exception(e)
+      @logger.error("failed processing a batch: #{e.message}")
+    end
+
+    def migrate_project(project)
+      result = nil
+      time = Benchmark.realtime do
+        result = ::Pages::MigrateLegacyStorageToDeploymentService.new(project, ignore_invalid_entries: @ignore_invalid_entries).execute
+      end
+
+      if result[:status] == :success
+        @logger.info("project_id: #{project.id} #{project.pages_path} has been migrated in #{time.round(2)} seconds")
+        @counters_lock.synchronize { @migrated += 1 }
+      else
+        @logger.error("project_id: #{project.id} #{project.pages_path} failed to be migrated in #{time.round(2)} seconds: #{result[:message]}")
+        @counters_lock.synchronize { @errored += 1 }
+      end
+    rescue => e
+      @counters_lock.synchronize { @errored += 1 }
+      @logger.error("project_id: #{project&.id} #{project&.pages_path} failed to be migrated: #{e.message}")
+      Gitlab::ErrorTracking.track_exception(e, project_id: project&.id)
+    end
+  end
+end