Copy original file to temp file always to prevent data loss

app/services/ci/create_trace_artifact_service.rb

@@ -8,7 +8,7 @@ module Ci
 
         temp_file!(JobArtifactUploader.workhorse_upload_path) do |temp_path|
           FileUtils.cp(stream.path, temp_path)
-          create_job_trace!(temp_path)
+          create_job_trace!(job, temp_path)
           FileUtils.rm(stream.path)
         end
       end
@@ -16,17 +16,17 @@ module Ci
 
     private
 
-    def create_job_trace!(path)
+    def create_job_trace!(job, path)
       job.create_job_artifacts_trace!(
         project: job.project,
         file_type: :trace,
-        file: UploadedFile.new(path, 'build.log', 'application/octet-stream')
+        file: UploadedFile.new(path, 'job.log', 'application/octet-stream')
       )
     end
 
     def temp_file!(temp_dir)
       FileUtils.mkdir_p(temp_dir)
-      temp_file = Tempfile.new('file', temp_dir)
+      temp_file = Tempfile.new('legacy-trace-tmp-', temp_dir)
       temp_file&.close
       yield(temp_file.path)
     ensure

spec/services/ci/create_trace_artifact_service_spec.rb

@@ -4,40 +4,56 @@ describe Ci::CreateTraceArtifactService do
   describe '#execute' do
     subject { described_class.new(nil, nil).execute(job) }
 
-    let(:job) { create(:ci_build) }
-
     context 'when the job does not have trace artifact' do
       context 'when the job has a trace file' do
-        before do
-          allow_any_instance_of(Gitlab::Ci::Trace)
-            .to receive(:default_path) { expand_fixture_path('trace/sample_trace') }
+        let!(:job) { create(:ci_build, :trace_live) }
+        let!(:legacy_path) { job.trace.read { |stream| return stream.path } }
 
-          allow_any_instance_of(JobArtifactUploader).to receive(:move_to_cache) { false }
-          allow_any_instance_of(JobArtifactUploader).to receive(:move_to_store) { false }
-        end
+        it { expect(File.exists?(legacy_path)).to be_truthy }
 
         it 'creates trace artifact' do
           expect { subject }.to change { Ci::JobArtifact.count }.by(1)
 
-          expect(job.job_artifacts_trace.read_attribute(:file)).to eq('sample_trace')
+          expect(File.exists?(legacy_path)).to be_falsy
+          expect(File.exists?(job.job_artifacts_trace.file.path)).to be_truthy
+          expect(job.job_artifacts_trace.exists?).to be_truthy
+          expect(job.job_artifacts_trace.file.filename).to eq('job.log')
         end
 
-        context 'when the job has already had trace artifact' do
+        context 'when failed to create trace artifact record' do
           before do
-            create(:ci_job_artifact, :trace, job: job)
+            # When ActiveRecord error happens
+            allow_any_instance_of(Ci::JobArtifact).to receive(:save).and_return(false)
+            allow_any_instance_of(Ci::JobArtifact).to receive_message_chain(:errors, :full_messages)
+              .and_return("Error")
+
+            subject rescue nil
+
+            job.reload
           end
 
-          it 'does not create trace artifact' do
-            expect { subject }.not_to change { Ci::JobArtifact.count }
+          it 'keeps legacy trace and removes trace artifact' do
+            expect(File.exists?(legacy_path)).to be_truthy
+            expect(job.job_artifacts_trace).to be_nil
           end
         end
       end
 
       context 'when the job does not have a trace file' do
+        let!(:job) { create(:ci_build) }
+
         it 'does not create trace artifact' do
           expect { subject }.not_to change { Ci::JobArtifact.count }
         end
       end
     end
+
+    context 'when the job has already had trace artifact' do
+      let!(:job) { create(:ci_build, :trace_artifact) }
+
+      it 'does not create trace artifact' do
+        expect { subject }.not_to change { Ci::JobArtifact.count }
+      end
+    end
   end
 end