Enable LFS chunked encoding

LFS currently doesn't use chunked transfers, which causes the whole body
to be read before it is stored. This causes 5+ GB uploads to be blocked
by Cloudflare on GitLab.com.

The LFS client will only enable this mode if the server sends the
`Transfer-Encoding: chunked` HTTP header.

This is guarded by the `lfs_chunked_encoding` feature flag to ensure
this mode doesn't cause issues.

Relates to https://gitlab.com/gitlab-org/gitlab/-/issues/285489

app/controllers/repositories/lfs_api_controller.rb

@@ -92,16 +92,26 @@ module Repositories
       {
         upload: {
           href: "#{project.http_url_to_repo}/gitlab-lfs/objects/#{object[:oid]}/#{object[:size]}",
-          header: {
-            Authorization: authorization_header,
-            # git-lfs v2.5.0 sets the Content-Type based on the uploaded file. This
-            # ensures that Workhorse can intercept the request.
-            'Content-Type': LFS_TRANSFER_CONTENT_TYPE
-          }.compact
+          header: upload_headers
         }
       }
     end
 
+    def upload_headers
+      headers = {
+        Authorization: authorization_header,
+        # git-lfs v2.5.0 sets the Content-Type based on the uploaded file. This
+        # ensures that Workhorse can intercept the request.
+        'Content-Type': LFS_TRANSFER_CONTENT_TYPE
+      }
+
+      if Feature.enabled?(:lfs_chunked_encoding, project)
+        headers['Transfer-Encoding'] = 'chunked'
+      end
+
+      headers
+    end
+
     def lfs_check_batch_operation!
       if batch_operation_disallowed?
         render(

changelogs/unreleased/sh-lfs-chunked-encoding.yml

+---
+title: Enable LFS chunked encoding
+merge_request: 48269
+author:
+type: changed

config/feature_flags/development/lfs_chunked_encoding.yml

+---
+name: lfs_chunked_encoding
+introduced_by_url: https://gitlab.com/gitlab-org/gitlab/-/jobs/864043673
+rollout_issue_url: https://gitlab.com/gitlab-org/gitlab/-/issues/285581
+milestone: '13.6'
+type: development
+group: 
+default_enabled: false

spec/requests/lfs_http_spec.rb

@@ -219,10 +219,12 @@ RSpec.describe 'Git LFS API and storage' do
   describe 'when handling LFS batch request' do
     let(:update_lfs_permissions) { }
     let(:update_user_permissions) { }
+    let(:lfs_chunked_encoding) { true }
 
     before do
       update_lfs_permissions
       update_user_permissions
+      stub_feature_flags(lfs_chunked_encoding: lfs_chunked_encoding)
       post_lfs_json batch_url(project), body, headers
     end
 
@@ -524,7 +526,24 @@ RSpec.describe 'Git LFS API and storage' do
           expect(json_response['objects']).to be_kind_of(Array)
           expect(json_response['objects'].first).to include(sample_object)
           expect(json_response['objects'].first['actions']['upload']['href']).to eq(objects_url(project, sample_oid, sample_size))
-          expect(json_response['objects'].first['actions']['upload']['header']).to include('Content-Type' => 'application/octet-stream')
+
+          headers = json_response['objects'].first['actions']['upload']['header']
+          expect(headers['Content-Type']).to eq('application/octet-stream')
+          expect(headers['Transfer-Encoding']).to eq('chunked')
+        end
+
+        context 'when lfs_chunked_encoding feature is disabled' do
+          let(:lfs_chunked_encoding) { false }
+
+          it 'responds with upload hypermedia link' do
+            expect(json_response['objects']).to be_kind_of(Array)
+            expect(json_response['objects'].first).to include(sample_object)
+            expect(json_response['objects'].first['actions']['upload']['href']).to eq(objects_url(project, sample_oid, sample_size))
+
+            headers = json_response['objects'].first['actions']['upload']['header']
+            expect(headers['Content-Type']).to eq('application/octet-stream')
+            expect(headers['Transfer-Encoding']).to be_nil
+          end
         end
 
         it_behaves_like 'process authorization header', renew_authorization: renew_authorization
@@ -548,7 +567,10 @@ RSpec.describe 'Git LFS API and storage' do
                 expect(lfs_object.projects.pluck(:id)).not_to include(project.id)
                 expect(lfs_object.projects.pluck(:id)).to include(other_project.id)
                 expect(json_response['objects'].first['actions']['upload']['href']).to eq(objects_url(project, sample_oid, sample_size))
-                expect(json_response['objects'].first['actions']['upload']['header']).to include('Content-Type' => 'application/octet-stream')
+
+                headers = json_response['objects'].first['actions']['upload']['header']
+                expect(headers['Content-Type']).to eq('application/octet-stream')
+                expect(headers['Transfer-Encoding']).to eq('chunked')
               end
 
               it_behaves_like 'process authorization header', renew_authorization: true
@@ -589,7 +611,10 @@ RSpec.describe 'Git LFS API and storage' do
 
               expect(json_response['objects'].last).to include(non_existing_object)
               expect(json_response['objects'].last['actions']['upload']['href']).to eq(objects_url(project, non_existing_object_oid, non_existing_object_size))
-              expect(json_response['objects'].last['actions']['upload']['header']).to include('Content-Type' => 'application/octet-stream')
+
+              headers = json_response['objects'].last['actions']['upload']['header']
+              expect(headers['Content-Type']).to eq('application/octet-stream')
+              expect(headers['Transfer-Encoding']).to eq('chunked')
             end
 
             it_behaves_like 'process authorization header', renew_authorization: true