Batchload blobs for diff generation

Gemfile

@@ -263,6 +263,8 @@ gem 'gettext_i18n_rails', '~> 1.8.0'
 gem 'gettext_i18n_rails_js', '~> 1.2.0'
 gem 'gettext', '~> 3.2.2', require: false, group: :development
 
+gem 'batch-loader'
+
 # Perf bar
 gem 'peek', '~> 1.0.1'
 gem 'peek-gc', '~> 0.0.2'

Gemfile.lock

@@ -73,6 +73,7 @@ GEM
       thread_safe (~> 0.3, >= 0.3.1)
     babosa (1.0.2)
     base32 (0.3.2)
+    batch-loader (1.1.1)
     bcrypt (3.1.11)
     bcrypt_pbkdf (1.0.0)
     benchmark-ips (2.3.0)
@@ -982,6 +983,7 @@ DEPENDENCIES
   awesome_print (~> 1.2.0)
   babosa (~> 1.0.2)
   base32 (~> 0.3.0)
+  batch-loader
   bcrypt_pbkdf (~> 1.0)
   benchmark-ips (~> 2.3.0)
   better_errors (~> 2.1.0)

app/controllers/projects/commit_controller.rb

@@ -22,12 +22,7 @@ class Projects::CommitController < Projects::ApplicationController
     apply_diff_view_cookie!
 
     respond_to do |format|
-      format.html do
-        # n+1: https://gitlab.com/gitlab-org/gitlab-ce/issues/37599
-        Gitlab::GitalyClient.allow_n_plus_1_calls do
-          render
-        end
-      end
+      format.html  { render }
       format.diff  { render text: @commit.to_diff }
       format.patch { render text: @commit.to_patch }
     end
@@ -112,7 +107,7 @@ class Projects::CommitController < Projects::ApplicationController
   end
 
   def commit
-    @noteable = @commit ||= @project.commit(params[:id])
+    @noteable = @commit ||= @project.commit_by(oid: params[:id])
   end
 
   def define_commit_vars

app/controllers/projects/merge_requests/diffs_controller.rb

@@ -10,10 +10,7 @@ class Projects::MergeRequests::DiffsController < Projects::MergeRequests::Applic
   def show
     @environment = @merge_request.environments_for(current_user).last
 
-    # n+1: https://gitlab.com/gitlab-org/gitlab-ce/issues/37431
-    Gitlab::GitalyClient.allow_n_plus_1_calls do
-      render json: { html: view_to_html_string("projects/merge_requests/diffs/_diffs") }
-    end
+    render json: { html: view_to_html_string("projects/merge_requests/diffs/_diffs") }
   end
 
   def diff_for_path

app/models/blob.rb

@@ -76,12 +76,24 @@ class Blob < SimpleDelegator
     new(blob, project)
   end
 
+  def self.lazy(project, commit_id, path)
+    BatchLoader.for(commit_id: commit_id, path: path).batch do |items, loader|
+      project.repository.blobs_at(items.map(&:values)).each do |blob|
+        loader.call({ commit_id: blob.commit_id, path: blob.path }, blob) if blob
+      end
+    end
+  end
+
   def initialize(blob, project = nil)
     @project = project
 
     super(blob)
   end
 
+  def inspect
+    "#<#{self.class.name} oid:#{id[0..8]} commit:#{commit_id[0..8]} path:#{path}>"
+  end
+
   # Returns the data of the blob.
   #
   # If the blob is a text based blob the content is converted to UTF-8 and any
@@ -95,7 +107,10 @@ class Blob < SimpleDelegator
   end
 
   def load_all_data!
-    super(project.repository) if project
+    # Endpoint needed: gitlab-org/gitaly#756
+    Gitlab::GitalyClient.allow_n_plus_1_calls do
+      super(project.repository) if project
+    end
   end
 
   def no_highlighting?

app/models/commit.rb

@@ -84,7 +84,7 @@ class Commit
   end
 
   def id
-    @raw.id
+    raw.id
   end
 
   def ==(other)
@@ -361,7 +361,7 @@ class Commit
     @deltas ||= raw.deltas
   end
 
-  def diffs(diff_options = nil)
+  def diffs(diff_options = {})
     Gitlab::Diff::FileCollection::Commit.new(self, diff_options: diff_options)
   end
 

app/models/repository.rb

@@ -478,6 +478,11 @@ class Repository
     nil
   end
 
+  # items is an Array like: [[oid, path], [oid1, path1]]
+  def blobs_at(items)
+    raw_repository.batch_blobs(items).map { |blob| Blob.decorate(blob, project) }
+  end
+
   def root_ref
     if raw_repository
       raw_repository.root_ref

changelogs/unreleased/zj-commit-show-n-1.yml

+---
+title: Fetch blobs in bulk when generating diffs
+merge_request:
+author:
+type: performance

config/initializers/batch_loader.rb

+Rails.application.config.middleware.use(BatchLoader::Middleware)

lib/gitlab/diff/file.rb

@@ -25,6 +25,10 @@ module Gitlab
         @repository = repository
         @diff_refs = diff_refs
         @fallback_diff_refs = fallback_diff_refs
+
+        # Ensure items are collected in the the batch
+        new_blob
+        old_blob
       end
 
       def position(position_marker, position_type: :text)
@@ -95,21 +99,15 @@ module Gitlab
       end
 
       def new_blob
-        return @new_blob if defined?(@new_blob)
-
-        sha = new_content_sha
-        return @new_blob = nil unless sha
+        return unless new_content_sha
 
-        @new_blob = repository.blob_at(sha, file_path)
+        Blob.lazy(repository.project, new_content_sha, file_path)
       end
 
       def old_blob
-        return @old_blob if defined?(@old_blob)
-
-        sha = old_content_sha
-        return @old_blob = nil unless sha
+        return unless old_content_sha
 
-        @old_blob = repository.blob_at(sha, old_path)
+        Blob.lazy(repository.project, old_content_sha, old_path)
       end
 
       def content_sha

lib/gitlab/diff/file_collection/base.rb

@@ -22,10 +22,7 @@ module Gitlab
         end
 
         def diff_files
-          # n+1: https://gitlab.com/gitlab-org/gitlab-ce/issues/37445
-          Gitlab::GitalyClient.allow_n_plus_1_calls do
-            @diff_files ||= @diffs.decorate! { |diff| decorate_diff!(diff) }
-          end
+          @diff_files ||= @diffs.decorate! { |diff| decorate_diff!(diff) }
         end
 
         def diff_file_with_old_path(old_path)

lib/gitlab/git/blob.rb

@@ -179,6 +179,8 @@ module Gitlab
               )
             end
           end
+        rescue Rugged::ReferenceError
+          nil
         end
 
         def rugged_raw(repository, sha, limit:)

lib/gitlab/git/repository.rb

@@ -1161,6 +1161,11 @@ module Gitlab
         Gitlab::Git::Blob.find(self, sha, path) unless Gitlab::Git.blank_ref?(sha)
       end
 
+      # Items should be of format [[commit_id, path], [commit_id1, path1]]
+      def batch_blobs(items, blob_size_limit: nil)
+        Gitlab::Git::Blob.batch(self, items, blob_size_limit: blob_size_limit)
+      end
+
       def commit_index(user, branch_name, index, options)
         committer = user_to_committer(user)
 

spec/controllers/projects/commit_controller_spec.rb

 require 'spec_helper'
 
 describe Projects::CommitController do
-  let(:project)  { create(:project, :repository) }
-  let(:user)     { create(:user) }
+  set(:project)  { create(:project, :repository) }
+  set(:user)     { create(:user) }
   let(:commit)   { project.commit("master") }
   let(:master_pickable_sha) { '7d3b0f7cff5f37573aea97cebfd5692ea1689924' }
   let(:master_pickable_commit)  { project.commit(master_pickable_sha) }
 
   before do
     sign_in(user)
-    project.team << [user, :master]
+    project.add_master(user)
   end
 
   describe 'GET show' do

spec/lib/gitlab/diff/file_spec.rb

@@ -116,12 +116,8 @@ describe Gitlab::Diff::File do
     end
 
     context 'when renamed' do
-      let(:commit) { project.commit('6907208d755b60ebeacb2e9dfea74c92c3449a1f') }
-      let(:diff_file) { commit.diffs.diff_file_with_new_path('files/js/commit.coffee') }
-
-      before do
-        allow(diff_file.new_blob).to receive(:id).and_return(diff_file.old_blob.id)
-      end
+      let(:commit) { project.commit('94bb47ca1297b7b3731ff2a36923640991e9236f') }
+      let(:diff_file) { commit.diffs.diff_file_with_new_path('CHANGELOG.md') }
 
       it 'returns false' do
         expect(diff_file.content_changed?).to be_falsey

spec/models/blob_spec.rb

@@ -16,6 +16,23 @@ describe Blob do
     end
   end
 
+  describe '.lazy' do
+    let(:project) { create(:project, :repository) }
+    let(:commit) { project.commit_by(oid: 'e63f41fe459e62e1228fcef60d7189127aeba95a') }
+
+    it 'fetches all blobs when the first is accessed' do
+      changelog = described_class.lazy(project, commit.id, 'CHANGELOG')
+      contributing = described_class.lazy(project, commit.id, 'CONTRIBUTING.md')
+
+      expect(Gitlab::Git::Blob).to receive(:batch).once.and_call_original
+      expect(Gitlab::Git::Blob).not_to receive(:find)
+
+      # Access property so the values are loaded
+      changelog.id
+      contributing.id
+    end
+  end
+
   describe '#data' do
     context 'using a binary blob' do
       it 'returns the data as-is' do

spec/models/diff_viewer/base_spec.rb

@@ -32,10 +32,8 @@ describe DiffViewer::Base do
       end
 
       context 'when the binaryness does not match' do
-        before do
-          allow(diff_file.old_blob).to receive(:binary?).and_return(false)
-          allow(diff_file.new_blob).to receive(:binary?).and_return(false)
-        end
+        let(:commit) { project.commit_by(oid: 'ae73cb07c9eeaf35924a10f713b364d32b2dd34f') }
+        let(:diff_file) { commit.diffs.diff_file_with_new_path('Gemfile.zip') }
 
         it 'returns false' do
           expect(viewer_class.can_render?(diff_file)).to be_falsey
@@ -60,8 +58,7 @@ describe DiffViewer::Base do
 
       context 'when the binaryness does not match' do
         before do
-          allow(diff_file.old_blob).to receive(:binary?).and_return(true)
-          allow(diff_file.new_blob).to receive(:binary?).and_return(true)
+          allow_any_instance_of(Blob).to receive(:binary?).and_return(true)
         end
 
         it 'returns false' do
@@ -77,12 +74,12 @@ describe DiffViewer::Base do
     end
 
     context 'when the file was renamed and only the old blob is supported' do
-      let(:commit) { project.commit('2f63565e7aac07bcdadb654e253078b727143ec4') }
+      let(:commit) { project.commit_by(oid: '2f63565e7aac07bcdadb654e253078b727143ec4') }
       let(:diff_file) { commit.diffs.diff_file_with_new_path('files/images/6049019_460s.jpg') }
 
       before do
         allow(diff_file).to receive(:renamed_file?).and_return(true)
-        allow(diff_file.new_blob).to receive(:extension).and_return('jpeg')
+        viewer_class.extensions = %w(notjpg)
       end
 
       it 'returns false' do
@@ -94,8 +91,7 @@ describe DiffViewer::Base do
   describe '#collapsed?' do
     context 'when the combined blob size is larger than the collapse limit' do
       before do
-        allow(diff_file.old_blob).to receive(:raw_size).and_return(512.kilobytes)
-        allow(diff_file.new_blob).to receive(:raw_size).and_return(513.kilobytes)
+        allow(diff_file).to receive(:raw_size).and_return(1025.kilobytes)
       end
 
       it 'returns true' do
@@ -113,8 +109,7 @@ describe DiffViewer::Base do
   describe '#too_large?' do
     context 'when the combined blob size is larger than the size limit' do
       before do
-        allow(diff_file.old_blob).to receive(:raw_size).and_return(2.megabytes)
-        allow(diff_file.new_blob).to receive(:raw_size).and_return(4.megabytes)
+        allow(diff_file).to receive(:raw_size).and_return(6.megabytes)
       end
 
       it 'returns true' do
@@ -132,8 +127,7 @@ describe DiffViewer::Base do
   describe '#render_error' do
     context 'when the combined blob size is larger than the size limit' do
       before do
-        allow(diff_file.old_blob).to receive(:raw_size).and_return(2.megabytes)
-        allow(diff_file.new_blob).to receive(:raw_size).and_return(4.megabytes)
+        allow(diff_file).to receive(:raw_size).and_return(6.megabytes)
       end
 
       it 'returns :too_large' do

spec/models/diff_viewer/server_side_spec.rb

 require 'spec_helper'
 
 describe DiffViewer::ServerSide do
-  let(:project) { create(:project, :repository) }
-  let(:commit) { project.commit('570e7b2abdd848b95f2f578043fc23bd6f6fd24d') }
-  let(:diff_file) { commit.diffs.diff_file_with_new_path('files/ruby/popen.rb') }
+  set(:project) { create(:project, :repository) }
+  let(:commit) { project.commit_by(oid: '570e7b2abdd848b95f2f578043fc23bd6f6fd24d') }
+  let!(:diff_file) { commit.diffs.diff_file_with_new_path('files/ruby/popen.rb') }
 
   let(:viewer_class) do
     Class.new(DiffViewer::Base) do
@@ -15,8 +15,7 @@ describe DiffViewer::ServerSide do
 
   describe '#prepare!' do
     it 'loads all diff file data' do
-      expect(diff_file.old_blob).to receive(:load_all_data!)
-      expect(diff_file.new_blob).to receive(:load_all_data!)
+      expect(Blob).to receive(:lazy).at_least(:twice)
 
       subject.prepare!
     end