Use exclusive lease when updating pages legacy storage

We don't need this lease right now, but we'll need it
to make sure that legacy storage isn't being touched
while we'll be migrating it to the zip storage

app/services/pages/legacy_storage_lease.rb

+# frozen_string_literal: true
+
+module Pages
+  module LegacyStorageLease
+    extend ActiveSupport::Concern
+
+    include ::ExclusiveLeaseGuard
+
+    LEASE_TIMEOUT = 1.hour
+
+    def lease_key
+      "pages_legacy_storage:#{project.id}"
+    end
+
+    def lease_timeout
+      LEASE_TIMEOUT
+    end
+  end
+end

app/services/projects/update_pages_service.rb

@@ -4,6 +4,9 @@ module Projects
   class UpdatePagesService < BaseService
     InvalidStateError = Class.new(StandardError)
     FailedToExtractError = Class.new(StandardError)
+    ExclusiveLeaseTaken = Class.new(StandardError)
+
+    include ::Pages::LegacyStorageLease
 
     BLOCK_SIZE = 32.kilobytes
     PUBLIC_DIR = 'public'
@@ -109,6 +112,17 @@ module Projects
     end
 
     def deploy_page!(archive_public_path)
+      deployed = try_obtain_lease do
+        deploy_page_unsafe!(archive_public_path)
+        true
+      end
+
+      unless deployed
+        raise ExclusiveLeaseTaken, "Failed to deploy pages - other deployment is in progress"
+      end
+    end
+
+    def deploy_page_unsafe!(archive_public_path)
       # Do atomic move of pages
       # Move and removal may not be atomic, but they are significantly faster then extracting and removal
       # 1. We move deployed public to previous public path (file removal is slow)

spec/services/pages/legacy_storage_lease_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe ::Pages::LegacyStorageLease do
+  let(:project) { create(:project) }
+
+  let(:implementation) do
+    Class.new do
+      include ::Pages::LegacyStorageLease
+
+      attr_reader :project
+
+      def initialize(project)
+        @project = project
+      end
+
+      def execute
+        try_obtain_lease do
+          execute_unsafe
+        end
+      end
+
+      def execute_unsafe
+        true
+      end
+    end
+  end
+
+  let(:service) { implementation.new(project) }
+
+  it 'allows method to be executed' do
+    expect(service).to receive :execute_unsafe
+
+    service.execute
+  end
+
+  context 'when another service holds the lease for the same project' do
+    around do |example|
+      implementation.new(project).try_obtain_lease do
+        example.run
+      end
+    end
+
+    it 'does not run guarded method' do
+      expect(service).not_to receive(:execute_unsafe)
+
+      expect(service.execute).to eq(nil)
+    end
+  end
+
+  context 'when another service holds the lease for the different project' do
+    around do |example|
+      implementation.new(create(:project)).try_obtain_lease do
+        example.run
+      end
+    end
+
+    it 'allows method to be executed' do
+      expect(service).to receive(:execute_unsafe).and_call_original
+
+      expect(service.execute).to eq(true)
+    end
+  end
+end

spec/services/projects/update_pages_service_spec.rb

@@ -69,6 +69,16 @@ RSpec.describe Projects::UpdatePagesService do
         expect(project.pages_metadatum.reload.pages_deployment_id).to eq(deployment.id)
       end
 
+      it 'fails if another deployment is in progress' do
+        subject.try_obtain_lease do
+          expect do
+            execute
+          end.to raise_error("Failed to deploy pages - other deployment is in progress")
+
+          expect(GenericCommitStatus.last.description).to eq("Failed to deploy pages - other deployment is in progress")
+        end
+      end
+
       it 'does not fail if pages_metadata is absent' do
         project.pages_metadatum.destroy!
         project.reload