Wait postgresql vacuum of deadtuples on merge_request_diff_files deletion

6 files changed, 87 insertions, 180 deletions

diff --git a/db/post_migrate/20180619121030_enqueue_delete_diff_files_workers.rb b/db/post_migrate/20180619121030_enqueue_delete_diff_files_workers.rb
index df30991737c..9e96aaf50a0 100644
--- a/db/post_migrate/20180619121030_enqueue_delete_diff_files_workers.rb
+++ b/db/post_migrate/20180619121030_enqueue_delete_diff_files_workers.rb
@@ -2,24 +2,15 @@ class EnqueueDeleteDiffFilesWorkers < ActiveRecord::Migration
   include Gitlab::Database::MigrationHelpers
 
   DOWNTIME = false
-  SCHEDULER = 'ScheduleDiffFilesDeletion'.freeze
-  TMP_INDEX = 'tmp_partial_diff_id_with_files_index'.freeze
+  MIGRATION = 'DeleteDiffFiles'.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
-
-    # We keep the index since this will be used async.
-    # Ideally we should remove it in an upcoming release.
-    BackgroundMigrationWorker.perform_async(SCHEDULER)
+    BackgroundMigrationWorker.perform_async(MIGRATION)
   end
 
   def down
-    if index_exists_by_name?(:merge_request_diffs, TMP_INDEX)
-      remove_concurrent_index_by_name(:merge_request_diffs, TMP_INDEX)
-    end
+    # no-op
   end
 end
diff --git a/lib/gitlab/background_migration/delete_diff_files.rb b/lib/gitlab/background_migration/delete_diff_files.rb
index e2c90fce6b1..36161285aac 100644
--- a/lib/gitlab/background_migration/delete_diff_files.rb
+++ b/lib/gitlab/background_migration/delete_diff_files.rb
@@ -8,6 +8,7 @@ module Gitlab
         self.table_name = 'merge_request_diffs'
 
         belongs_to :merge_request
+        has_many :merge_request_diff_files
 
         include EachBatch
       end
@@ -18,41 +19,73 @@ module Gitlab
         include EachBatch
       end
 
-      def perform(merge_request_diff_id)
-        merge_request_diff = MergeRequestDiff.find_by(id: merge_request_diff_id)
+      BATCH = 5_000
+      DEAD_TUPLES_THRESHOLD = 50_000
+      VACUUM_WAIT_TIME = 5.minutes
 
-        return unless merge_request_diff
-        return unless should_delete_diff_files?(merge_request_diff)
+      def perform
+        diffs_with_files = MergeRequestDiff
+          .joins(:merge_request)
+          .where("merge_requests.state = 'merged'")
+          .where('merge_requests.latest_merge_request_diff_id IS NOT NULL')
+          .where('merge_requests.latest_merge_request_diff_id != merge_request_diffs.id')
+          .where("merge_request_diffs.state NOT IN ('without_files', 'empty')")
 
-        MergeRequestDiff.transaction do
-          merge_request_diff.update_column(:state, 'without_files')
-
-          # 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
-          #
-          MergeRequestDiffFile.where(merge_request_diff_id: merge_request_diff.id).delete_all
+        diffs_with_files.each_batch(of: BATCH) do |batch, index|
+          wait_deadtuple_vacuum(index)
+          prune_diff_files(batch, index)
+        end
+      end
+
+      def wait_deadtuple_vacuum(index)
+        db_klass = Gitlab::Database
+
+        if defined?(db_klass) && db_klass.respond_to?(:postgresql?) && db_klass.postgresql?
+          while diff_files_dead_tuples_count >= DEAD_TUPLES_THRESHOLD
+            log_info("Dead tuple threshold hit on merge_request_diff_files (#{index}th batch): " \
+                     "#{diff_files_dead_tuples_count}, waiting 5 minutes")
+            sleep VACUUM_WAIT_TIME
+          end
         end
       end
 
       private
 
-      def should_delete_diff_files?(merge_request_diff)
-        return false if merge_request_diff.state == 'without_files'
+      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]
+
+        if dead_tuple.present?
+          dead_tuple['n_dead_tup'].to_i
+        else
+          0
+        end
+      end
 
-        merge_request = merge_request_diff.merge_request
+      def prune_diff_files(batch, index)
+        diff_ids = batch.pluck(:id)
 
-        return false unless merge_request.state == 'merged'
-        return false if merge_request_diff.id == merge_request.latest_merge_request_diff_id
+        removed = 0
+        updated = 0
+
+        MergeRequestDiff.transaction do
+          updated = MergeRequestDiff.where(id: diff_ids)
+            .update_all(state: 'without_files')
+          removed = MergeRequestDiffFile.where(merge_request_diff_id: diff_ids)
+            .delete_all
+        end
+
+        log_info("#{index}th batch - 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
diff --git a/lib/gitlab/background_migration/schedule_diff_files_deletion.rb b/lib/gitlab/background_migration/schedule_diff_files_deletion.rb
deleted file mode 100644
index 6442468836b..00000000000
--- a/lib/gitlab/background_migration/schedule_diff_files_deletion.rb
+++ /dev/null
@@ -1,61 +0,0 @@
-# frozen_string_literal: true
-# rubocop:disable Metrics/AbcSize
-# rubocop:disable Style/Documentation
-
-module Gitlab
-  module BackgroundMigration
-    class ScheduleDiffFilesDeletion
-      class MergeRequestDiff < ActiveRecord::Base
-        self.table_name = 'merge_request_diffs'
-
-        has_many :merge_request_diff_files
-
-        include EachBatch
-      end
-
-      ITERATION_BATCH = 1000
-      DELETION_BATCH = 1000 # per minute
-      MIGRATION = 'DeleteDiffFiles'
-
-      # Considering query times and Redis writings, this should take around 2
-      # hours to complete.
-      def perform
-        diffs_with_files = MergeRequestDiff.where.not(state: %w(without_files empty))
-
-        # This will be increased for each scheduled job
-        process_job_in = 1.second
-
-        # explain (analyze, buffers) example for the iteration:
-        #
-        # Index Only Scan using tmp_index_20013 on merge_request_diffs  (cost=0.43..1630.19 rows=60567 width=4) (actual time=0.047..9.572 rows=56976 loops=1)
-        #   Index Cond: ((id >= 764586) AND (id < 835298))
-        #   Heap Fetches: 8
-        #   Buffers: shared hit=18188
-        # Planning time: 0.752 ms
-        # Execution time: 12.430 ms
-        #
-        diffs_with_files.reorder(nil).each_batch(of: ITERATION_BATCH) do |relation, scheduler_index|
-          relation.each do |diff|
-            BackgroundMigrationWorker.perform_in(process_job_in, MIGRATION, [diff.id])
-
-            diff_files_count = diff.merge_request_diff_files.reorder(nil).count
-
-            # We should limit on 1000 diff files deletion per minute to avoid
-            # replication lag issues.
-            #
-            interval = (diff_files_count.to_f / DELETION_BATCH).minutes
-            process_job_in += interval
-          end
-        end
-
-        log_days_to_process_all_jobs(process_job_in)
-      end
-
-      def log_days_to_process_all_jobs(seconds_to_process)
-        days_to_process_all_jobs = (seconds_to_process / 60 / 60 / 24).to_i
-        Rails.logger.info("Gitlab::BackgroundMigration::DeleteDiffFiles will take " \
-                          "#{days_to_process_all_jobs} days to be processed")
-      end
-    end
-  end
-end
diff --git a/spec/lib/gitlab/background_migration/delete_diff_files_spec.rb b/spec/lib/gitlab/background_migration/delete_diff_files_spec.rb
index d8497315e2d..f128c9ecf1b 100644
--- a/spec/lib/gitlab/background_migration/delete_diff_files_spec.rb
+++ b/spec/lib/gitlab/background_migration/delete_diff_files_spec.rb
@@ -4,19 +4,19 @@ describe Gitlab::BackgroundMigration::DeleteDiffFiles, :migration, schema: 20180
   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
 
       it 'deletes all merge request diff files' do
-        expect { described_class.new.perform(merge_request_diff.id) }
+        expect { described_class.new.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 { described_class.new.perform }
           .to change { merge_request_diff.reload.state }
           .from('collected').to('without_files')
       end
@@ -25,7 +25,7 @@ describe Gitlab::BackgroundMigration::DeleteDiffFiles, :migration, schema: 20180
         expect(described_class::MergeRequestDiffFile).to receive_message_chain(:where, :delete_all)
           .and_raise
 
-        expect { described_class.new.perform(merge_request_diff.id) }
+        expect { described_class.new.perform }
           .to raise_error
 
         merge_request_diff.reload
@@ -40,7 +40,7 @@ describe Gitlab::BackgroundMigration::DeleteDiffFiles, :migration, schema: 20180
       merge_request.create_merge_request_diff
       merge_request_diff = merge_request.merge_request_diffs.first
 
-      expect { described_class.new.perform(merge_request_diff.id) }
+      expect { described_class.new.perform }
         .not_to change { merge_request_diff.merge_request_diff_files.count }
         .from(20)
     end
@@ -52,7 +52,7 @@ describe Gitlab::BackgroundMigration::DeleteDiffFiles, :migration, schema: 20180
 
       merge_request_diff.clean!
 
-      expect { described_class.new.perform(merge_request_diff.id) }
+      expect { described_class.new.perform }
         .not_to change { merge_request_diff.merge_request_diff_files.count }
         .from(20)
     end
@@ -61,9 +61,26 @@ describe Gitlab::BackgroundMigration::DeleteDiffFiles, :migration, schema: 20180
       merge_request = create(:merge_request, :merged)
       merge_request_diff = merge_request.merge_request_diff
 
-      expect { described_class.new.perform(merge_request_diff.id) }
+      expect { described_class.new.perform }
         .not_to change { merge_request_diff.merge_request_diff_files.count }
         .from(20)
     end
   end
+
+  describe '#wait_deadtuple_vacuum' do
+    it 'sleeps process for VACUUM_WAIT_TIME when hitting 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(worker).to receive(:sleep).with(described_class::VACUUM_WAIT_TIME).once
+
+      worker.wait_deadtuple_vacuum(1)
+    end
+  end
 end
diff --git a/spec/lib/gitlab/background_migration/schedule_diff_files_deletion_spec.rb b/spec/lib/gitlab/background_migration/schedule_diff_files_deletion_spec.rb
deleted file mode 100644
index 04f20b75531..00000000000
--- a/spec/lib/gitlab/background_migration/schedule_diff_files_deletion_spec.rb
+++ /dev/null
@@ -1,73 +0,0 @@
-require 'spec_helper'
-
-describe Gitlab::BackgroundMigration::ScheduleDiffFilesDeletion, :migration, schema: 20180619121030 do
-  describe '#perform' do
-    let(:merge_request_diffs) { table(:merge_request_diffs) }
-    let(:diff_files) { table(:merge_request_diff_files) }
-    let(:merge_requests) { table(:merge_requests) }
-    let(:namespaces) { table(:namespaces) }
-    let(:projects) { table(:projects) }
-
-    def diff_file_params(extra_params = {})
-      extra_params.merge(new_file: false,
-                         renamed_file: false,
-                         too_large: false,
-                         deleted_file: false,
-                         a_mode: 'foo',
-                         b_mode: 'bar',
-                         new_path: 'xpto',
-                         old_path: 'kux',
-                         diff: 'content')
-    end
-
-    def create_diffs(id:, files_number:, state: 'collected')
-      merge_request_diffs.create!(id: id, merge_request_id: 1, state: state)
-      files_number.times.to_a.each do |index|
-        params = diff_file_params(merge_request_diff_id: id, relative_order: index)
-
-        diff_files.create!(params)
-      end
-    end
-
-    before do
-      stub_const("#{described_class.name}::DELETION_BATCH", 10)
-
-      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')
-    end
-
-    it 'correctly schedules diff file deletion workers' do
-      Sidekiq::Testing.fake! do
-        Timecop.freeze do
-          create_diffs(id: 1, files_number: 25)
-          create_diffs(id: 2, files_number: 11)
-          create_diffs(id: 3, files_number: 4, state: 'without_files')
-          create_diffs(id: 4, files_number: 5, state: 'empty')
-          create_diffs(id: 5, files_number: 9)
-
-          worker = described_class.new
-
-          expect(worker).to receive(:log_days_to_process_all_jobs).with(1.second + 2.5.minutes + 1.1.minutes + 0.9.minutes)
-
-          worker.perform
-
-          expect(described_class::MIGRATION).to be_scheduled_delayed_migration(1.second, 1)
-          expect(described_class::MIGRATION).to be_scheduled_delayed_migration(1.second + 2.5.minutes, 2)
-          expect(described_class::MIGRATION).to be_scheduled_delayed_migration(1.second + 2.5.minutes + 1.1.minutes, 5)
-          expect(BackgroundMigrationWorker.jobs.size).to eq(3)
-        end
-      end
-    end
-  end
-
-  describe '#days_to_process_all_jobs' do
-    it 'logs how many days it will take to run all jobs' do
-      expect(Rails).to receive_message_chain(:logger, :info)
-        .with("Gitlab::BackgroundMigration::DeleteDiffFiles will take 3 days to be processed")
-
-      described_class.new.log_days_to_process_all_jobs(3.days.seconds)
-    end
-  end
-end
diff --git a/spec/migrations/enqueue_delete_diff_files_workers_spec.rb b/spec/migrations/enqueue_delete_diff_files_workers_spec.rb
index 3d19c6fcc10..803830d81cf 100644
--- a/spec/migrations/enqueue_delete_diff_files_workers_spec.rb
+++ b/spec/migrations/enqueue_delete_diff_files_workers_spec.rb
@@ -2,11 +2,11 @@ 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 file deletion scheduler' do
+  it 'correctly schedules diff files deletion' do
     Sidekiq::Testing.fake! do
       expect(BackgroundMigrationWorker)
         .to receive(:perform_async)
-        .with(described_class::SCHEDULER)
+        .with(described_class::MIGRATION)
         .and_call_original
 
       migrate!