Merge branch 'add-back-mr-diff-deletion-migration' into 'master'

Add back MR diff deletion migration

See merge request gitlab-org/gitlab-ce!20331

db/post_migrate/20180619121030_enqueue_delete_diff_files_workers.rb

+class EnqueueDeleteDiffFilesWorkers < ActiveRecord::Migration
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+  SCHEDULER = 'ScheduleDiffFilesDeletion'.freeze
+  TMP_INDEX = 'tmp_partial_diff_id_with_files_index'.freeze
+
+  disable_ddl_transaction!
+
+  def up
+    unless index_exists_by_name?(:merge_request_diffs, TMP_INDEX)
+      add_concurrent_index(:merge_request_diffs, :id, where: "(state NOT IN ('without_files', 'empty'))", name: TMP_INDEX)
+    end
+
+    BackgroundMigrationWorker.perform_async(SCHEDULER)
+
+    # We don't remove the index since it's going to be used on DeleteDiffFiles
+    # worker. We should remove it in an upcoming release.
+  end
+
+  def down
+    if index_exists_by_name?(:merge_request_diffs, TMP_INDEX)
+      remove_concurrent_index_by_name(:merge_request_diffs, TMP_INDEX)
+    end
+  end
+end

lib/gitlab/background_migration/delete_diff_files.rb

@@ -4,41 +4,77 @@
 module Gitlab
   module BackgroundMigration
     class DeleteDiffFiles
-      def perform(merge_request_diff_id)
-        merge_request_diff = MergeRequestDiff.find_by(id: merge_request_diff_id)
+      class MergeRequestDiff < ActiveRecord::Base
+        self.table_name = 'merge_request_diffs'
 
-        return unless merge_request_diff
-        return unless should_delete_diff_files?(merge_request_diff)
+        belongs_to :merge_request
+        has_many :merge_request_diff_files
+      end
 
-        MergeRequestDiff.transaction do
-          merge_request_diff.update_column(:state, 'without_files')
+      class MergeRequestDiffFile < ActiveRecord::Base
+        self.table_name = 'merge_request_diff_files'
+      end
 
-          # explain (analyze, buffers) when deleting 453 diff files:
-          #
-          # Delete on merge_request_diff_files  (cost=0.57..8487.35 rows=4846 width=6) (actual time=43.265..43.265 rows=0 loops=1)
-          #   Buffers: shared hit=2043 read=259 dirtied=254
-          #   ->  Index Scan using index_merge_request_diff_files_on_mr_diff_id_and_order on merge_request_diff_files  (cost=0.57..8487.35 rows=4846 width=6) (actu
-          # al time=0.466..26.317 rows=453 loops=1)
-          #         Index Cond: (merge_request_diff_id = 463448)
-          #         Buffers: shared hit=17 read=84
-          # Planning time: 0.107 ms
-          # Execution time: 43.287 ms
+      DEAD_TUPLES_THRESHOLD = 50_000
+      VACUUM_WAIT_TIME = 5.minutes
+
+      def perform(ids)
+        @ids = ids
+
+        # We should reschedule until deadtuples get in a desirable
+        # state (e.g. < 50_000). That may take more than one reschedule.
         #
-          MergeRequestDiffFile.where(merge_request_diff_id: merge_request_diff.id).delete_all
+        if should_wait_deadtuple_vacuum?
+          reschedule
+          return
         end
+
+        prune_diff_files
+      end
+
+      def should_wait_deadtuple_vacuum?
+        return false unless Gitlab::Database.postgresql?
+
+        diff_files_dead_tuples_count >= DEAD_TUPLES_THRESHOLD
       end
 
       private
 
-      def should_delete_diff_files?(merge_request_diff)
-        return false if merge_request_diff.state == 'without_files'
+      def reschedule
+        BackgroundMigrationWorker.perform_in(VACUUM_WAIT_TIME, self.class.name.demodulize, [@ids])
+      end
+
+      def diffs_collection
+        MergeRequestDiff.where(id: @ids)
+      end
+
+      def diff_files_dead_tuples_count
+        dead_tuple =
+          execute_statement("SELECT n_dead_tup FROM pg_stat_all_tables "\
+                            "WHERE relname = 'merge_request_diff_files'")[0]
 
-        merge_request = merge_request_diff.merge_request
+        dead_tuple&.fetch('n_dead_tup', 0).to_i
+      end
+
+      def prune_diff_files
+        removed = 0
+        updated = 0
 
-        return false unless merge_request.state == 'merged'
-        return false if merge_request_diff.id == merge_request.latest_merge_request_diff_id
+        MergeRequestDiff.transaction do
+          updated = diffs_collection.update_all(state: 'without_files')
+          removed = MergeRequestDiffFile.where(merge_request_diff_id: @ids).delete_all
+        end
+
+        log_info("Removed #{removed} merge_request_diff_files rows, "\
+                 "updated #{updated} merge_request_diffs rows")
+      end
+
+      def execute_statement(sql)
+        ActiveRecord::Base.connection.execute(sql)
+      end
 
-        true
+      def log_info(message)
+        Rails.logger.info("BackgroundMigration::DeleteDiffFiles - #{message}")
       end
     end
   end

lib/gitlab/background_migration/schedule_diff_files_deletion.rb

+# frozen_string_literal: true
+# rubocop:disable Style/Documentation
+
+module Gitlab
+  module BackgroundMigration
+    class ScheduleDiffFilesDeletion
+      class MergeRequestDiff < ActiveRecord::Base
+        self.table_name = 'merge_request_diffs'
+
+        belongs_to :merge_request
+
+        include EachBatch
+      end
+
+      DIFF_BATCH_SIZE = 5_000
+      INTERVAL = 5.minutes
+      MIGRATION = 'DeleteDiffFiles'
+
+      def perform
+        diffs = MergeRequestDiff
+          .from("(#{diffs_collection.to_sql}) merge_request_diffs")
+          .where('merge_request_diffs.id != merge_request_diffs.latest_merge_request_diff_id')
+          .select(:id)
+
+        diffs.each_batch(of: DIFF_BATCH_SIZE) do |relation, index|
+          ids = relation.pluck(:id)
+
+          BackgroundMigrationWorker.perform_in(index * INTERVAL, MIGRATION, [ids])
+        end
+      end
+
+      private
+
+      def diffs_collection
+        MergeRequestDiff
+          .joins(:merge_request)
+          .where("merge_requests.state = 'merged'")
+          .where('merge_requests.latest_merge_request_diff_id IS NOT NULL')
+          .where("merge_request_diffs.state NOT IN ('without_files', 'empty')")
+          .select('merge_requests.latest_merge_request_diff_id, merge_request_diffs.id')
+      end
+    end
+  end
+end

spec/lib/gitlab/background_migration/delete_diff_files_spec.rb

 require 'spec_helper'
 
-describe Gitlab::BackgroundMigration::DeleteDiffFiles, :migration, schema: 20180626125654 do
+describe Gitlab::BackgroundMigration::DeleteDiffFiles, :migration, schema: 20180619121030 do
   describe '#perform' do
     context 'when diff files can be deleted' do
       let(:merge_request) { create(:merge_request, :merged) }
-      let(:merge_request_diff) do
+      let!(:merge_request_diff) do
         merge_request.create_merge_request_diff
         merge_request.merge_request_diffs.first
       end
 
+      let(:perform) do
+        described_class.new.perform(MergeRequestDiff.pluck(:id))
+      end
+
       it 'deletes all merge request diff files' do
-        expect { described_class.new.perform(merge_request_diff.id) }
+        expect { perform }
           .to change { merge_request_diff.merge_request_diff_files.count }
           .from(20).to(0)
       end
 
       it 'updates state to without_files' do
-        expect { described_class.new.perform(merge_request_diff.id) }
+        expect { perform }
           .to change { merge_request_diff.reload.state }
           .from('collected').to('without_files')
       end
 
       it 'rollsback if something goes wrong' do
-        expect(MergeRequestDiffFile).to receive_message_chain(:where, :delete_all)
+        expect(described_class::MergeRequestDiffFile).to receive_message_chain(:where, :delete_all)
           .and_raise
 
-        expect { described_class.new.perform(merge_request_diff.id) }
+        expect { perform }
           .to raise_error
 
         merge_request_diff.reload
@@ -35,35 +39,35 @@ describe Gitlab::BackgroundMigration::DeleteDiffFiles, :migration, schema: 20180
       end
     end
 
-    it 'deletes no merge request diff files when MR is not merged' do
-      merge_request = create(:merge_request, :opened)
-      merge_request.create_merge_request_diff
-      merge_request_diff = merge_request.merge_request_diffs.first
-
-      expect { described_class.new.perform(merge_request_diff.id) }
-        .not_to change { merge_request_diff.merge_request_diff_files.count }
-        .from(20)
-    end
-
-    it 'deletes no merge request diff files when diff is marked as "without_files"' do
+    it 'reschedules itself when should_wait_deadtuple_vacuum' do
       merge_request = create(:merge_request, :merged)
-      merge_request.create_merge_request_diff
-      merge_request_diff = merge_request.merge_request_diffs.first
+      first_diff = merge_request.merge_request_diff
+      second_diff = merge_request.create_merge_request_diff
+
+      Sidekiq::Testing.fake! do
+        worker = described_class.new
+        allow(worker).to receive(:should_wait_deadtuple_vacuum?) { true }
 
-      merge_request_diff.clean!
+        worker.perform([first_diff.id, second_diff.id])
 
-      expect { described_class.new.perform(merge_request_diff.id) }
-        .not_to change { merge_request_diff.merge_request_diff_files.count }
-        .from(20)
+        expect(described_class.name.demodulize).to be_scheduled_delayed_migration(5.minutes, [first_diff.id, second_diff.id])
+        expect(BackgroundMigrationWorker.jobs.size).to eq(1)
+      end
+    end
   end
 
-    it 'deletes no merge request diff files when diff is the latest' do
-      merge_request = create(:merge_request, :merged)
-      merge_request_diff = merge_request.merge_request_diff
+  describe '#should_wait_deadtuple_vacuum?' do
+    it 'returns true when hitting merge_request_diff_files hits DEAD_TUPLES_THRESHOLD', :postgresql do
+      worker = described_class.new
+      threshold_query_result = [{ "n_dead_tup" => described_class::DEAD_TUPLES_THRESHOLD.to_s }]
+      normal_query_result = [{ "n_dead_tup" => '3' }]
+
+      allow(worker)
+        .to receive(:execute_statement)
+        .with(/SELECT n_dead_tup */)
+        .and_return(threshold_query_result, normal_query_result)
 
-      expect { described_class.new.perform(merge_request_diff.id) }
-        .not_to change { merge_request_diff.merge_request_diff_files.count }
-        .from(20)
+      expect(worker.should_wait_deadtuple_vacuum?).to be(true)
     end
   end
 end

spec/lib/gitlab/background_migration/schedule_diff_files_deletion_spec.rb

+require 'spec_helper'
+
+describe Gitlab::BackgroundMigration::ScheduleDiffFilesDeletion, :migration, schema: 20180619121030 do
+  describe '#perform' do
+    let(:merge_request_diffs) { table(:merge_request_diffs) }
+    let(:merge_requests) { table(:merge_requests) }
+    let(:namespaces) { table(:namespaces) }
+    let(:projects) { table(:projects) }
+
+    before do
+      stub_const("#{described_class.name}::DIFF_BATCH_SIZE", 3)
+
+      namespaces.create!(id: 1, name: 'gitlab', path: 'gitlab')
+      projects.create!(id: 1, namespace_id: 1, name: 'gitlab', path: 'gitlab')
+
+      merge_requests.create!(id: 1, target_project_id: 1, source_project_id: 1, target_branch: 'feature', source_branch: 'master', state: 'merged')
+
+      merge_request_diffs.create!(id: 1, merge_request_id: 1, state: 'collected')
+      merge_request_diffs.create!(id: 2, merge_request_id: 1, state: 'empty')
+      merge_request_diffs.create!(id: 3, merge_request_id: 1, state: 'without_files')
+      merge_request_diffs.create!(id: 4, merge_request_id: 1, state: 'collected')
+      merge_request_diffs.create!(id: 5, merge_request_id: 1, state: 'collected')
+      merge_request_diffs.create!(id: 6, merge_request_id: 1, state: 'collected')
+      merge_request_diffs.create!(id: 7, merge_request_id: 1, state: 'collected')
+
+      merge_requests.update(1, latest_merge_request_diff_id: 7)
+    end
+
+    it 'correctly schedules diff file deletion workers' do
+      Sidekiq::Testing.fake! do
+        Timecop.freeze do
+          described_class.new.perform
+
+          expect(described_class::MIGRATION).to be_scheduled_delayed_migration(5.minutes, [1, 4, 5])
+
+          expect(described_class::MIGRATION).to be_scheduled_delayed_migration(10.minutes, [6])
+
+          expect(BackgroundMigrationWorker.jobs.size).to eq(2)
+        end
+      end
+    end
+  end
+end

spec/migrations/enqueue_delete_diff_files_workers_spec.rb

+require 'spec_helper'
+require Rails.root.join('db', 'post_migrate', '20180619121030_enqueue_delete_diff_files_workers.rb')
+
+describe EnqueueDeleteDiffFilesWorkers, :migration, :sidekiq do
+  it 'correctly schedules diff files deletion schedulers' do
+    Sidekiq::Testing.fake! do
+      expect(BackgroundMigrationWorker)
+        .to receive(:perform_async)
+        .with(described_class::SCHEDULER)
+        .and_call_original
+
+      migrate!
+
+      expect(BackgroundMigrationWorker.jobs.size).to eq(1)
+    end
+  end
+end