Merge branch 'sh-skip-lfs-updates-mirroring' into 'master'

Skip updating LFS objects in mirror updates if repository has not changed

Closes #38256

See merge request gitlab-org/gitlab!21744

changelogs/unreleased/sh-skip-lfs-updates-mirroring.yml

+---
+title: Skip updating LFS objects in mirror updates if repository has not changed
+merge_request: 21744
+author:
+type: performance

ee/app/services/projects/update_mirror_service.rb

@@ -24,12 +24,17 @@ module Projects
         return error("The mirror user is not allowed to push code to all branches on this project.")
       end
 
+      checksum_before = project.repository.checksum
+
       update_tags do
         project.fetch_mirror(forced: true)
       end
 
       update_branches
-      update_lfs_objects
+
+      # Updating LFS objects is expensive since it requires scanning for blobs with pointers.
+      # Let's skip this if the repository hasn't changed.
+      update_lfs_objects if project.repository.checksum != checksum_before
 
       success
     rescue Gitlab::Shell::Error, Gitlab::Git::BaseError, UpdateError => e

ee/spec/services/projects/update_mirror_service_spec.rb

@@ -325,13 +325,26 @@ describe Projects::UpdateMirrorService do
       end
     end
 
-    context 'updating Lfs objects' do
+    context 'updating LFS objects' do
+      context 'when repository does not change' do
+        before do
+          allow(project).to receive(:lfs_enabled?).and_return(true)
+        end
+
+        it 'does not attempt to update LFS objects' do
+          expect(Projects::LfsPointers::LfsImportService).not_to receive(:new)
+
+          service.execute
+        end
+      end
+
+      context 'when repository changes' do
         before do
           stub_fetch_mirror(project)
         end
 
         context 'when Lfs is disabled in the project' do
-        it 'does not update Lfs objects' do
+          it 'does not update LFS objects' do
             allow(project).to receive(:lfs_enabled?).and_return(false)
             expect(Projects::LfsPointers::LfsObjectDownloadListService).not_to receive(:new)
 
@@ -344,7 +357,7 @@ describe Projects::UpdateMirrorService do
             allow(project).to receive(:lfs_enabled?).and_return(true)
           end
 
-        it 'updates Lfs objects' do
+          it 'updates LFS objects' do
             expect(Projects::LfsPointers::LfsImportService).to receive(:new).and_call_original
             expect_any_instance_of(Projects::LfsPointers::LfsObjectDownloadListService).to receive(:execute).and_return({})
 
@@ -383,6 +396,7 @@ describe Projects::UpdateMirrorService do
           end
         end
       end
+    end
 
     it "fails when the mirror user doesn't have access" do
       stub_fetch_mirror(project)