Ensure that only persisted chunk can be flushed

app/models/ci/build_trace_chunk.rb

@@ -138,13 +138,15 @@ module Ci
     #
     def persist_data!
       in_lock(*lock_params) do         # exclusive Redis lock is acquired first
+        raise FailedToPersistDataError, 'Modifed build trace chunk detected' if has_changes_to_save?
+
         self.reset.then do |chunk|     # we ensure having latest lock_version
           chunk.unsafe_persist_data!   # we migrate the data and update data store
         end
       end
     rescue ActiveRecord::StaleObjectError
       raise FailedToPersistDataError, <<~MSG
-        data migration race condition detected
+        Data migration race condition detected
 
         store: #{data_store}
         build: #{build.id}

spec/models/ci/build_trace_chunk_spec.rb

@@ -597,6 +597,14 @@ RSpec.describe Ci::BuildTraceChunk, :clean_gitlab_redis_shared_state do
               expect { build_trace_chunk.persist_data! }
                 .to raise_error(described_class::FailedToPersistDataError)
             end
+
+            it 'does not allow flushing unpersisted chunk' do
+              build_trace_chunk.checksum = '12345'
+
+              expect { build_trace_chunk.persist_data! }
+                .to raise_error(described_class::FailedToPersistDataError,
+                                /Modifed build trace chunk detected/)
+            end
           end
         end
       end