Add pages_file_entries to plan_limits

Adds file entries limit to pages deployments:
https://gitlab.com/gitlab-org/gitlab/-/issues/320793.

GitLab Pages daemon actually caches index of each archive in memory,
so archives with too many entries can increase the memory usage.

To prevent this, we adding the limit. It also will work for
self-managed,  but we provide a workaround to change it in docs.

Changelog: added

app/services/projects/update_pages_service.rb

@@ -157,6 +157,10 @@ module Projects
       entries_count = build.artifacts_metadata_entry("", recursive: true).entries.count
       sha256 = build.job_artifacts_archive.file_sha256
 
+      if pages_file_entries_limit > 0 && entries_count > pages_file_entries_limit
+        raise InvalidStateError, "pages site contains #{entries_count} file entries, while limit is set to #{pages_file_entries_limit}"
+      end
+
       deployment = nil
       File.open(artifacts_path) do |file|
         deployment = project.pages_deployments.create!(file: file,
@@ -198,6 +202,12 @@ module Projects
       max_pages_size
     end
 
+    def pages_file_entries_limit
+      return 0 unless Feature.enabled?(:pages_limit_entries_count, project, default_enabled: :yaml)
+
+      project.actual_limits.pages_file_entries
+    end
+
     def tmp_path
       @tmp_path ||= File.join(::Settings.pages.path, TMP_EXTRACT_PATH)
     end

config/feature_flags/development/pages_limit_entries_count.yml

+---
+name: pages_limit_entries_count
+introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/merge_requests/64925/diffs
+rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/334765
+milestone: '14.1'
+type: development
+group: group::release
+default_enabled: false

db/migrate/20210611082822_add_pages_file_entries_to_plan_limits.rb

+# frozen_string_literal: true
+
+class AddPagesFileEntriesToPlanLimits < ActiveRecord::Migration[6.1]
+  def change
+    add_column(:plan_limits, :pages_file_entries, :integer, default: 100_000, null: false)
+  end
+end

db/schema_migrations/20210611082822

+28b31b6e8aba1b8feec2b9a29b5f91f7145431be5d8b9875bddb8183f89700f7
\ No newline at end of file

db/structure.sql

@@ -16475,7 +16475,8 @@ CREATE TABLE plan_limits (
     ci_daily_pipeline_schedule_triggers integer DEFAULT 0 NOT NULL,
     ci_max_artifact_size_running_container_scanning integer DEFAULT 0 NOT NULL,
     ci_max_artifact_size_cluster_image_scanning integer DEFAULT 0 NOT NULL,
-    ci_jobs_trace_size_limit integer DEFAULT 100 NOT NULL
+    ci_jobs_trace_size_limit integer DEFAULT 100 NOT NULL,
+    pages_file_entries integer DEFAULT 100000 NOT NULL
 );
 
 CREATE SEQUENCE plan_limits_id_seq

doc/administration/instance_limits.md

@@ -457,6 +457,21 @@ installation, run the following in the [GitLab Rails console](operations/rails_c
 Plan.default.actual_limits.update!(ci_max_artifact_size_junit: 10)
 ```
 
+### Number of files per GitLab Pages web-site
+
+The total number of file entries (including directories and symlinks) is limited to `100000` per
+GitLab Pages website.
+
+This is the default limit for all [GitLab self-managed and SaaS plans](https://about.gitlab.com/pricing/).
+
+You can update the limit in your self-managed instance using the
+[GitLab Rails console](operations/rails_console.md#starting-a-rails-console-session).
+For example, to change the limit to `100`:
+
+```ruby
+Plan.default.actual_limits.update!(pages_file_entries: 100)
+```
+
 ### Number of registered runners per scope
 
 > [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/321368) in GitLab 13.12.

spec/services/projects/update_pages_service_spec.rb

@@ -158,6 +158,21 @@ RSpec.describe Projects::UpdatePagesService do
         expect(execute).not_to eq(:success)
       end
 
+      it 'limits pages file count' do
+        create(:plan_limits, :default_plan, pages_file_entries: 2)
+
+        expect(execute).not_to eq(:success)
+
+        expect(GenericCommitStatus.last.description).to eq("pages site contains 3 file entries, while limit is set to 2")
+      end
+
+      it 'does not limit pages file count if feature is disabled' do
+        stub_feature_flags(pages_limit_entries_count: false)
+        create(:plan_limits, :default_plan, pages_file_entries: 2)
+
+        expect(execute).to eq(:success)
+      end
+
       it 'removes pages after destroy' do
         expect(PagesWorker).to receive(:perform_in)
         expect(project.pages_deployed?).to be_falsey