Ensure consistency when creating a new build trace chunk

This commit increases consistency when a build trace chunk is created.

app/models/ci/build_trace_chunk.rb

@@ -81,15 +81,17 @@ module Ci
       # database, what is especially important in EE. This method does not
       # change the behavior in CE.
       #
-      def with_consistent_reads(project, &block)
-        return yield unless Feature.enabled?(
-          :gitlab_ci_trace_read_consistency, project, type: :development, default_enabled: false
-        )
+      def with_read_consistency(build, &block)
+        return yield unless consistent_reads_enabled?(build)
 
         ::Gitlab::Database::Consistency
           .with_read_consistency(&block)
       end
 
+      def consistent_reads_enabled?(build)
+        Feature.enabled?(:gitlab_ci_trace_read_consistency, build.project, type: :development, default_enabled: false)
+      end
+
       ##
       # Sometimes we do not want to read raw data. This method makes it easier
       # to find attributes that are just metadata excluding raw data.
@@ -168,7 +170,7 @@ module Ci
       in_lock(lock_key, **lock_params) do # exclusive Redis lock is acquired first
         raise FailedToPersistDataError, 'Modifed build trace chunk detected' if has_changes_to_save?
 
-        self.class.with_consistent_reads(build.project) do
+        self.class.with_read_consistency(build) do
           self.reset.then { |chunk| chunk.unsafe_persist_data! }
         end
       end

lib/gitlab/ci/trace/checksum.rb

@@ -63,7 +63,7 @@ module Gitlab
         #
         def trace_chunks
           strong_memoize(:trace_chunks) do
-            Ci::BuildTraceChunks.with_read_consistency(build.project) do
+            ::Ci::BuildTraceChunk.with_read_consistency(build) do
               build.trace_chunks.persisted
                 .select(::Ci::BuildTraceChunk.metadata_attributes)
             end

lib/gitlab/ci/trace/chunked_io.rb

@@ -227,12 +227,20 @@ module Gitlab
         end
         # rubocop: enable CodeReuse/ActiveRecord
 
-        def build_chunk
-          @chunks_cache[chunk_index] = ::Ci::BuildTraceChunk.new(build: build, chunk_index: chunk_index)
+        def next_chunk
+          @chunks_cache[chunk_index] = begin
+            if ::Ci::BuildTraceChunk.consistent_reads_enabled?(build)
+              ::Ci::BuildTraceChunk
+                .safe_find_or_create_by(build: build, chunk_index: chunk_index)
+            else
+              ::Ci::BuildTraceChunk
+                .new(build: build, chunk_index: chunk_index)
+            end
+          end
         end
 
         def ensure_chunk
-          current_chunk || build_chunk
+          current_chunk || next_chunk || current_chunk
         end
 
         # rubocop: disable CodeReuse/ActiveRecord